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Pathology week x – Blood cell disorders ver.2

Red Blood Cells and Bleeding Disorders

Anaemia

- reduction in blood oxygen transport capacity, usually due to reduced circulating rbc mass

- reflected by low Hb and Hct

- in most anaemias increased erythropoietin production induces erythroid marrow dysplasia

- classification can be based on mechanisms of production, or on basis of red cell MCV etc

Classification of Anaemia According to Underlying Mechanism

Blood Loss

Acute: trauma

Chronic: lesions of GI tract, gynaecologic disturbances

Increased Rate of Destruction (Haemolytic Anaemias)

Intrinsic (intracorpuscular) abnormalities of rbcs

Hereditary

RBC membrane disorders

- cytoskeleton: spherocytosis, elliptocytosis

- lipid synthesis: selective increase in membrane lecithin

RBC enzyme deficiencies

Glycolytic enzymes: pyruvate kinase deficiency, hexokinase deficiency

Enzymes of hexose monophosphate shunt: G6PD, glutathione synthetase

Disorders of haemoglobin synthesis

Deficient globin synthesis: thalassaemia

Structurally abnormal globin synthesis (haemoglobinopathies): sickle cell anaemia, unstable haemoglobins

Acquired

Membrane defect: paroxysmal nocturnal haemoglobinuria

Extrinsic (extracorpuscular) abnormalities

Antibody mediated

Isohemagglutinins: transfusion reactions, erythroblastosis fetalis

Autoantibodies: idiopathic (primary), drug-associated, SLE, malignant neoplasms, mycoplasmal infection

Mechanical trauma to red cells

Microangiopathic haemolytic anaemias: TTP, DIC

Cardiac traumatic haemolytic anaemia

Infections: malaria, hookworm

Chemical injury: lead poisoning

Sequestration in mononuclear phagocyte system: hypersplenism

Impaired RBC Production

Disturbance of proliferation/differentiation of stem cells: aplastic anaemia, pure red cell aplasia, renal failure,

endocrine disorders

Disturbance of proliferation and maturation of erythroblasts

Defective DNA synthesis: deficiency or impaired use of vitamin B12 and folic acid (megaloblastic anaemias)

Defective haemoglobin synthesis

Deficient haem synthesis: iron deficiency

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Deficient globin synthesis: thalassemias

Unknown or multiple mechanisms: sideroblastic anaemia, chronic infections, marrow infiltrations

Anaemias of Blood Loss

- clinical/morphological reactions depend on rate of haemorrhage

o acute blood loss: loss of blood volume, may lead to shock or death; after 4-5/7 increase EPO causes

compensatory increase in marrow production (reticulocytosis)

o chronic blood loss: anaemia results when iron reserves depleted; with iron supplementation increased

marrow production (reticulocytosis) in several days

Haemolytic Anaemias

- premature rbc destruction (normal life span 120 days), accumulation of haemoglobin catabolites (eg bilirubin) and

marked increased erythropoiesis with reticulocytosis

- haemolysis intravascular or extravascular:

o intravascular: rbcs damaged by mechanical injury (eg microangiopathic haemolytic anaemia) or

complement (eg mismatched transfusions)

� haemoglobinaemia

� haemoglobinuria

� haemosiderinuria

� conjugated hyperbilirubinaemia

� reduced haptoglobin (protein that binds haemoglobin)

o extravascular: in mononuclear phagocytes of spleen

� predisposing factors: rbc membrane injury, reduced deformability, opsonisation

� symptoms similar to intravascular, without haemoglobinaemia/haemoglobinuria

Hereditary Spherocytosis

- 75% autosomal dominant

- rbc cytoskeletal membrane protein defects render erythrocytes spheroidal, less deformable, vulnerable to splenic

sequestration and destruction

- defects lead to deficiencies in spectrin – a meshwork protein of rbc membranes

- morph: cells small, lack central pallor; congestion in splenic cords of Billroth; bone marrow shows normoblastic

hyperplasia - clinically: variable; anaemia, moderate splenomegaly, jaundice, 50% gallstones from bilirubin

- infections can trigger haemolytic crisis with massive haemolysis or aplastic crisis (transient suppression of

erythropoiesis by parvovirus)

- mean cell Hb conc increased due to cellular dehydration

Glucose-6-Phosphate Dehydrogenase Deficiency (G6PD)

- G6PD enzyme in hexose monophosphate shunt that produces reduced glutathione (molecule that protects rbcs from

oxidative injury)

- if deficient, oxidant stresses induce haemoglobin denaturation

- altered Hb precipitates as Heinz bodies, attach to inner cell membrane, reduce deformability and increase

susceptibility to splenic macrophage destruction

- Heinz bodies damage cell membranes causing intra and extravascular haemolysis

- X-linked, several variants, only G6PD A- and G6PD Mediterranean cause haemolysis

- older rbcs haemolyse in response to some drugs (antimalarials)

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- fava beans can cause haemolysis (favism) because generate oxidants

Sickle Cell Anaemia

- hereditary haemoglobinopathy from abnormal Hb (HbS) due to substitution valine for glutamic acid at 6th position

of β-globin chain

- HbA (α2β2) changed to HbS (α2βs

2)

- deoxygenated HbS aggregation and polymerization into long chain that deform (sickle) rbcs

- factors influencing sickling:

o amount of HbS and its interaction with other Hb chains in the cells (most important):

� heterozygotes ~40% HbS, rest is HbA which interacts with HbS and interferes with aggregation

– little tendency to sickle

� homozygotes mostly HbS, full-blown disease

� other β globin chains influence sickling

• HbF (fetal) interacts weakly with HbS so infants < 6 months no disease

• HbC, another mutant Hb, greater tendency to aggregate with HbS so pts heterozygotic

for both HbS and HbC have more severe disease (HbSC)

o mean corpuscular Hb conc (MCHC):

� high HbS concs increase rate of contact and interaction between HbS molecules

• dehydration increases MCHC – incr sickling and occlusion small vessels

� diseases that reduce MCHC (eg α-thalassaemia) decrease sickling severity

o capillary bed transit times:

� normal transit rate fast - significant deoxygenation, therefore sickling can’t occur

� sickling usually confined to areas of sluggish blood flow (eg spleen, marrow), or in areas of

inflammation

- consequences of sickling:

o chronic haemolysis: sickling damages rbc membranes so cells irreversibly sickled; rigid, nondeformable

cells prone to sequestration + destruction; survival rbc shortened to 20/7

o microvacular occlusions: due to inelasticity and propensity to adhere to capillary endothelium – causes

hypoxia and infarction

- morph: splenomegaly, then scarring and shrinkage (autosplenectomy) due to repeat episodes; bone marrow shows

normoblastic hyperplasia; microvascular occlusions produce infarction

- clinically:

o chronic haemolytic anaemia (hyperbilirubinaemia, gallstones)

o vaso-occlusive crises (painful ischaemic necrosis – bone, lung, liver, brain, penis, spleen)

o aplastic crisis (transient suppression erythropoiesis triggered by parvovirus)

o progressive splenic fibrosis and impairment of alternate complement pathway

� predisposes to infections: Salmonella, encapsulated – Strep pneumo, H infl

Thalassaemia Syndromes

- heterozygous group of mendelian disorders, characterized by defects that lead to reduced synthesis of α or βglobin

chains

- α chains encoded by single gene on chr 11

- β chains encoded by 2 closely linked genes on chr 16

Genetic Defects:

- β-thalassaemia syndromes: deficient synthesis of β-globin:

o βo-thalassaemia – total absence βglobin chains in homozygous state

o β+-thalassaemia – reduced β-globin synthesis in homozygous state

o several point mutations affecting transcription, processing, translation β–globin mRNA

- α-thalassaemia: reduced α-globin synthesis due to deletion of one or more α-globin genes

Pathophysiology:

- consequences of low globin chain due to both low intracellular Hb (hypochromia) and relative excess of other

chain

- β-thalassemia:

o excess free α chains aggregate into insoluble inclusions in rbcs, leading to premature destruction of

maturing erythroblasts in marrow (ineffective erythropoiesis) and lysis of mature rbcs in spleen

(haemolysis)

o severe anaemia causes compensatory expansion of erythropoeitic marrow, encroaching on cortical bone,

causing skeletal abnormalities in children

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o ineffective erythropoiesis also associated with excess absorption of iron – with repeat transfusions leads to

iron overload

- α-thalassaemia:

o due to imbalanced synthesis of α and non-α chains (γ in infancy, β after 6/12)

o free β chains form unstable tetramers (HbH) that damage rbcs and their precursors

o free γ chains form stable tetramers (HbBarts) that bind O2 with excessive avidity, resulting in tissue

hypoxia

Clinical and Genetic Classification of Thalassemias

Clinical Nomenclature Genotype Disease

β-Thalassemias

Thalassemia major Homozygous β0-

thalassemia (β0/β

0)

Severe; requires blood transfusions

Homozygous β+-

thalassemia (β+/β

+)

Thalassemia intermedia β0/β

β+/β

+

Severe, but does not require regular blood transfusions

Thalassemia minor β0/β

β+/β

Asymptomatic, mild or absent anaemia; rbc abnormalities seen

α-Thalassemias

Hydrops fetails -/--/- Lethal in utero without transfusions

HbH disease -/--/α Severe; resembles β-thalassemia intermedia

α-Thalassemia trait -/-α/α (Asian)

-/α-/α (black African)

Asymptomatic, like β-thalassemia minor

Silent carrier -/αα/α Asymptomatic; no red cell abnormality

Clinical classification:

β-Thalassaemia:

- classification based on severity of anaemia – based on genetic defect (β+ or β

0) as well as gene dosage

(homozygous/heterozygous)

- Thalassaemia major: homozygous either β+ or β

0, severe transfusion-dependent anaemia

o Hb 30-60

o most common in Mediterranean countries, Africa, SE Asia

o peripheral blood: anisocytosis (variable cell size), microcytic hypochromic rbcs, target cells, strippled or

fragmented rbcs

o without transfusions is lethal

o transfusion lessen anaemia and suppress secondary changes related to excess erythropoiesis (bone

deformities)

o multiple transfusions, morbidity due to cardiac failure from iron overload and secondary

haemochromatosis

- Thalassaemia minor: heterozygotes, usually asymptomatic due to sufficient β-globin synthesis

o more common form, affects same ethnic groups

o peripheral blood: hypochromia, microcytosis, basophilic stippling, target cells

o Hb electrophoresis shows increased HbA2 (α2δ2 Hb)

- Thalassaemia intermedia: clinical features and severity between major and minor; heterozygotes

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Α-Thalassaemia:

- classification and severity related to number of α-globin genes deleted

- silent carrier state: asymptomatic, single gene deletion

- α-Thalassaemia trait: either 1 chromosome has both α-globing genes or each has one deletion, clinically similar to

β-thalassaemia minor

- Haemoglobin H (HbH) disease: deletion 3 α-globin genes, decreased synthesis α chain, formation unstable

tetramers or excess β-globin (HbH)

- Hydrops fetalis: deletion all 4 genes, in fetus excess γ-globin chains form tetramers (HbBarts) with high O2 affinity

and inability to release O2 into tissue; not compatible with life

Paroxysmal Nocturnal Haemoglobinuria (PNH)

- rare acquired haemolytic anaemia due to a membrane defect, chronic intravascular haemolysis

- rbc ↑ sensitivity to complement-mediated lysis - deficiency family of proteins in cell membrane

- complement activated spontaneously

- platelets also affected so predisposition to thrombosis, esp portal, cerebral and hepatic veins

- may be autoimmune response to GPI-linked proteins on haemopoietic stem cells

- sometimes associated with aplastic anaemia, rarely transforms to acute leukaemia

Immunohaemolytic Anaemias

- haemolysis due to anti-red cell antibodies

- direct Coombs test detects Abs and complement on rbcs

- classified on nature of Abs and presence/absence of underlying disorder

Immunohaemolytic Anaemias

Warm Antibody Type

Ab is IgG type, does not usually fix complement, is active at 37°C

Primary (idiopathic 60%)

Secondary (Lymphomas and leukemias, other neoplastic diseases, autoimmune disorder (esp SLE), drugs)

Cold Agglutinin Type

Abs are IgM and most active in vitro at 0° to 4°C

Abs dissociate > 30°C; agglutination cells by IgM and complement fixation only in cool parts of body (fingers, ears)

Acute (mycoplasmal infection, EBV)

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Chronic (Idiopathic; assoc with lymphoma)

Cold Haemolysins (Paroxysmal Cold Haemoglobinuria)

IgG Abs bind red cells at low temperature, fix complement, cause haemolysis when temp raised above 30°C

usually post infection – Mycoplasma, measles, mumps, influenza

Haemolytic Anaemias resulting from trauma to RBCs

- trauma to rbcs causes fragmentation and intravascular haemolysis

- blood shows fragmented rbcs (schistocytes)

- underlying conditions:

o prosthetic heart valve with turbulence and shear forces

o diffuse narrowing of microvasculature due to fibrin deposition eg DIC

Anaemias of diminished erythropoiesis

- impaired rbc production, various causes - nutrient def (iron, B12, folate), stem cell failure

Megaloblastic Anaemia

- usually due to deficiency B12 or folate

- morphology:

o abnormally large erythroid precursors (megaloblasts)

o ineffective erythropoiesis (megaloblasts die in BM), compensatory megaloblastic hyperplasia

o prominent anisocytosis, due to abnormal erythropoiesis, with abnormally large and oval rbcs (macro-oval-

ocytes); mean corpuscular volume >110fL

o abnormal granulopoiesis with giant metamyelocytes and hypersegmented neutrophils

- pathophysiology:

o B12 and folate essential for production of thymidine (building block of DNA)

o deficiency causes deranged or inadequate DNA synthesis

o anaemia due to ineffective erythropoiesis and abnormal rbcs that are susceptible to premature removal by

phagocytes

o B12/folate def also affect other dividing cells – myeloid precursors, GI epithelium

o ineffective granulopoiesis and thrombopoiesis can result in pancytopenia

Causes of Megaloblastic Anaemia

Vitamin B12 Deficiency

Decreased intake (inadequate diet, vegetarianism)

Impaired absorption

Intrinsic factor deficiency (pernicious anaemia, gastrectomy)

Malabsorption states

Diffuse intestinal disease (lymphoma, systemic sclerosis)

Ileal resection, ileitis

Competitive parasitic uptake (fish tapeworm infestation)

Bacterial overgrowth in blind loops and diverticula of bowel

Increased requirement (pregnancy, hyperthyroidism, disseminated cancer)

Folic Acid Deficiency

Decreased intake (inadequate diet-alcoholism, infancy)

Impaired absorption (malabsorption states, intrinsic intestinal disease, anticonvulsants, oral contraceptives)

Increased loss (haemodialysis)

Increased requirement (pregnancy, infancy, disseminated cancer, markedly increased haematopoiesis)

Impaired use (folic acid antagonists)

Unresponsive to Vitamin B12 or Folic Acid Therapy

Metabolic inhibitors of DNA synthesis and/or folate metabolism (methotrexate)

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Anaemias of Vitamin B12 Deficiency – Pernicious Anaemia

- main source of Vit B12 is animal products

Pernicious Anaemia:

- autoimmune to gastric parietal cells, results in chronic atrophic gastritis/parietal cell loss

- deficiency in IF production; autoreactive T cells produce antibodies:

o type I Abs block binding of B12 to IF

o type II Abs prevent IF or IF-B12 complex from binding to ileal receptor

o Abs against gastric proton pump bind to parietal cells and affect acid secretion

- significant association with other autoimmune diseases of adrenals and thyroid

- morphology:

o BM – megaloblastic erythroid hyperplasia, giant myelocytes, metamyelocytes,

o GI – changes of atrophic glossitis: tongue shiny and red, gastric fundal atrophy with absence of parietal

cells, atrophic gastric mucosa replaced by mucus-secreting goblet cells (“intestinalization”)

o CNS – 75% - demyelination of dorsal and lateral spinal cord tracts, if advanced spastic paresis and

sensory ataxia (folate deficiency doesn’t cause neuro effects)

- clinically: insidious onset, 40-60 years, symptoms of anaemia and spinal tract involvement

o increased risk gastric cancer

o diagnosis by B12 levels, film, anti-IF Abs and reticulocytosis after parenteral B12 admin

Vitamin B12 absorption:

- peptic digestion releases dietary Vit B12

- bound to salivary proteins - R binders

- R-B12 complexes are digested in duodenum by

pancreatic proteases

- released B12 binds to intrinsic factor (IF)

(protein secreted by parietal cells of gastric

fundus)

- IF-B12 complexes bind to IF receptors in distal

ileum epithelium

- absorbed B12 complexes with transcobalamin II

and is transported to tissues

Deficiencies in B12 result from impaired absorption,

with several causes:

- achlorhydria (elderly), impairs B12 release from

R protein-bound form

- gastrectomy, leads to loss of IF

- pernicious anaemia

- resection of distal ileum, prevents absorption of

IF-B12 complex

- malabsorption syndromes

- increased requirements (eg pregnancy)

- inadequate diet (uncommon due to large body

reserves

Anaemia of Folate Deficiency

- megaloblastic anaemia the same as B12 deficiency but without gastric atrophy and neurological

- reduced serum or rbc folate levels

- causes:

o inadequate intake (alcoholics, elderly)

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o malabsorption syndromes (tropical and nontropical sprue)

o increased demand (pregnancy, infancy, disseminated cancer)

o use of folate antagonists (methotrexate)

Iron Deficiency Anaemia

- common cause of anaemia

- duodenum primary site for absorption

- 20% haem iron absorbable, 1-2% nonhaem iron absorbable

- total body iron content 2g women, 6g men

- in all tissues, particularly liver, spleen, BM, skeletal muscle

- 80% body iron is in haemoglobin, myoglobin and iron-containing enzymes (catalase and cytochromes); remainder

stored in haemosiderin and ferritin

- ferritin good indicator of body iron stores

Aetiology:

- negative iron balance due to:

o low dietary intake (rare, most diets adequate)

o malabsorption (sprue, celiac disease, gastrectomy)

o excessive demand (pregnancy, infancy)

o chronic blood loss (most important cause; GI (ulcers, cancer, haemorrhoids, hookworms) or female GU

(menorrhagia, metrorrhagia, cancers)

Clinically:

- peripheral blood: rbcs hypochromic, microcytic, variable shape (poikilocytosis)

- BM: mild hyperplasia of normoblasts, loss of sideroblasts, absent iron in macrophages

- other organs: severe deficiency – depletion of essential iron-containing enzymes: alopecia, koilonychias, atrophic

tongue and gastric mucosa

o Plummer-Vinson triad: hypo microcytic anaemia, atrophic glossitis, oesophageal webs

- diagnosis: clinical and low serum iron and ferritin, increased total plasma iron-binding capacity, reduced plasma

transferrin saturation

Iron Metabolism

- haem iron enters mucosal cells directly via haem transporter

- nonhaem iron (Fe3+

) first reduced to ferrous iron (Fe2+

) by membrane-bound cytochrome B, then transported into

cell by transport protein DMT1

- some of absorbed iron transported across basolateral membrane, and bound to plasma transferrin for distribution

through body

- basolateral transport involves ferriportin, a membrane transport, and hephaestin, an iron oxidase which transforms

it back to Fe3+

- remaining intracellular iron bound to ferritin, excreted in faeces when epithelium sloughed

- iron haemostasis regulated in part by hepcidin, a small liver-derived polypeptide that blocks duodenal uptake by

inhibiting ferroportin activity

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Internal Iron Cycle:

- plasma iron bound to transferring, transported to

marrow

- in BM is transferred to developing red cells and

incorporated into haemoglobin

- mature rbcs released into circulation and after

120 days are ingested by macrophages in

reticuloendothelial system (RES)

- in RES iron extracted from haemoglobin and

returned to plasma, completing the cycle

Anaemia of Chronic Disease

- chronic inflammatory mediators (TNF, IL1) increase release of hepcidin from liver

- hepcidin blocks ferroportin activity on macrophages so iron is sequestered away from erythroid progenators

- serum iron low but ferritin high

- inflammatory mediators also reduce epo production, exacerbating anaemia

- normocytic/normochromic or microcytic/hypochromic

- trmt of underlying condition corrects anaemia, epo partially effective

Aplastic Anaemia

- failure or suppression of multipotent myeloid stem cells

- neutropenia, anaemia, thrombocytopenia (pancytopenia)

Major Causes of Aplastic Anaemia

Acquired

Idiopathic (65%)

Primary stem cell defect

Immune mediated

Myelotoxic agents

Dose related (alkylating agents, antimetabolites - vincristine, benzene, chloramphenicol, inorganic arsenicals)

Idiosyncratic (chloramphenicol, streptomycin, chlorpromazine, insecticides (DDT, parathion)

Physical agents (whole-body irradiation)

Viral infections (nonA, nonB, nonC, nonG Hep, CMV, EBV, VZV)

Inherited

Fanconi anaemia

Pathogenesis:

- stem cell alterations due to environmental insults, drug exposure or infection

- idiopathic cases:

o damaged stem cells can produce progeny expressing neo-antigens that evoke an autoimmune reaction by

T cells , or give rise to a clonal population with reduced proliferative capacity, leading to marrow aplasia

Morphology:

- hypocellular marrow (cells replaced by fat cells)

- secondary effects due to granulocytopenia (infection), thrombocytopenia (bleeding), anaemia

- no splenomegaly

- if due to chemical, withdrawal of agent may cause recovery

- often bone marrow transplant or immunosuppression required

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Other forms of marrow failure:

- CRF: multifactorial, mainly due to inadequate epo production

- liver disease: anaemia due to bone marrow failure, exacerbated by variceal bleeding or folate deficiency

- myelophthisic anaemia: space-occupying lesions the destroy BM – often mets

Polycythaemia

- relative or absolute increase in concentration of rbcs

o relative: due to decreased plasma volume – haemoconcentration (dehydration) or due to stress

polycythaemia (Gaisbock syndrome)

o absolute:

� primary: increased rbcs due to myeloid neoplasm – polycythaemia vera

� secondary: increased rbcs due to increased epo

• appropriate (lung disease, altitude, cyanotic heart disease)

• inappropriate (epo-secreting tumours – renal cell/HCC)

Bleeding Disorders - due to increase blood vessel fragility, platelet disorders, coagulation disorders or combination

o bleeding time (time for standardized skin puncture to stop bleeding)

� prolonged: defect in platelet number or function

o platelet count

o prothrombin time (PT) - tests extrinsic and common coagulation pathways

� prolonged: deficiency or dysfunction factor V, VII, X, prothrombin, fibrinogen

o partial thromboplastin time (PTT) - tests intrinsic and common clotting pathways

� prolonged: deficiency or dysfunction of factor V, VIII, IX, X, XI, XII, prothrombin, fibrinogen

o specialized tests (clotting factor levels)

Increased Vascular Fragility

- relatively common, don’t usually cause serious bleeding

- petechial and purpuric haemorrhages

- platelet count and coagulation time normal

- bleeding time variable

- causes:

o infections (meningococcus, rickettsia – due to vasculitis or DIC)

o drug reactions (secondary to immune complex deposition in vessel walls with hypersensitivity vasculitis)

o poor vascular support (abnormal collagen – scurvy, Ehlers-Danlos; Cushings; vascular wall amyloid

deposition)

o Henoch-Schonlein purpura (systemic hypersensitivity reaction of unknown cause characterized by

purpuric rash, abdo pain, polyarthralgia, acute GN; associated with vascular and glomerular mesangial

deposition of immune complexes)

Thrombocytopenia

- petechial bleeding, most often from small vessels of skin and mucous membranes

- must be severe (<2)) before bleeding evident

Causes of Thrombocytopenia

Decreased production of platelets

Generalized diseases of bone marrow

Aplastic anaemia: congenital and acquired

Marrow infiltration: leukaemia, disseminated cancer

Selective impairment of platelet production

Drug-induced: alcohol, thiazides, cytotoxic drugs

Infections: measles, human immunodeficiency virus (HIV)

Ineffective megakaryopoiesis

Megaloblastic anaemia, Myelodysplastic syndromes

Decreased platelet survival

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Immunologic destruction

Autoimmune: ITP, SLE

Isoimmune: post-transfusion and neonatal

Drug-associated: quinidine, heparin, sulfa compounds

Infections: EBV, HIV (immune complex injury, antiplt Abs and HIV-induced suppression of

megakaryocytes, CMV)

Nonimmunologic destruction

DIC, TTP, giant haemangiomas, micrangiopathic haemolytic anaemias

Sequestration

Hypersplenism

Dilutional

Immune Thrombocytopenia Purpura (ITP)

- two forms of antibody-mediated platelet destruction:

o acute ITP: self-limited, often in children post viral infection (rubella, CMV, hep, EBV)

� platelet destruction due to transient antiplatelet autoantibodies

o chronic ITP: platelet autoantibodies (made in spleen) directed toward one of two platelet antigens – plt

membrane glycoprotein complexes IIb/IIIa or Ib/IX

� destruction of Ab-coated platelets in spleen

� splenectomy benefits 80%

Clinically:

- chronic: adults, esp women childbearing age

- long history easy bruising or nosebleeds

- sometimes sudden on shower of petechial haemorrhages or internal bleed (melaena, haematuria)

- subarach/intracerebral bleed rare but possible

- idiopathic or secondary to SLE/AIDS/drugs/lymphoid neoplasms

- diagnosis: clinically and BMA

- prolonged bleeding time, normal PT/PTT

- no splenomegaly

Drug-Induced Thrombocytopenia

- many drugs can cause immune-mediated platelet destruction by acting as haptens or forming immune complexes

that deposit on platelet membranes

- drug-induced Abs cause rapid removal of platelets via reticuloendothelial system

- heparin stimulates formation of Abs directed against a complex of heparin and platelet factor 4

o leads to thrombi in arteries and veins

- withdrawal of drug causes improvement

Thrombotic Thrombocytopenic Purpura (TTP) and Haemolytic Uraemic Syndrome (HUS)

- two related disorders within the spectrum of thrombotic microangiopathies

- thrombocytopenia, microangiopathic haemolytic anaemia, fever, transient neurological deficits (TTP), renal failure

(HUS)

- some overlap of symptoms

- most symptoms due to widespread hyaline microthrombi in arterioles and capillaries composed of dense

aggregates of platelets and fibrin

Pathophysiology:

- clinically similar to DIC, but without activation of clotting system

- TTP and HUS have similar features but different causes

- TTP – associated with inherited or acquired deficiencies in ADAMTS13 (serum metalloprotease that limits size of

vWF multimers in plasma

o in its absence very high MW vWF multimers accumulate that promote platelet aggregation in

microcirculation

o acquired – Abs against ADAMTS13

- HUS – commonly follow GI infections with verotoxin-producing E coli

o Verotoxin injures endothelial cells and promotes dysregulated platelet activation and aggregation

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Clinically:

- acquired TTP affects women

- HUS often in children and elderly after food poisoning

- trmt: plasma exchange or plasmapheresis (removes Abs in acquired TTP or toxins in HUS)

- endothelial injury due to other causes (toxic drugs, radiation) may cause chronic HUS

Haemorrhagic Disorders Related to Defective Platelet Functions

- prolonged bleeding time but normal platelet count

- congenital or acquired

- congenital:

o defective platelet adhesion (autosomal recessive Bernard-Soulier syndrome, deficient plt membrane

glycoprotein complex GpIb/IX – the plt receptor for vWF – necessary for plt adhesion)

o defective platelet aggregation (thrombasthenia – autosomal recessive deficiency plt membrane

glycoprotein GpIIb/GpIIIa – involved in binding fibrinogen)

o disorders of platelet secretion (initial plt aggregation with collagen or ATP normal but subsequent plt

responses impaired)

- acquired:

o aspirin: potent inhibitor of enzyme COX and can suppress the synthesis of thromboxane A2, necessary for

plt aggregation

o uraemia: complex pathogenesis, caused by defects in platelet function

Haemorrhagic Diatheses Related to Abnormalities in Clotting Factors

- clotting abnormalities acquired or hereditary

- acquired: usually associated with multiple clotting abnormalities

o Vit K deficiency causes decreased production of factors II, VII, IX, X and protein C

o liver makes virtually all clotting factors so severe liver disease will cause bleeding

o DIC produces deficiency of multiple coagulation factors

- hereditary: typically single clotting factor

o Haemophilia A and B

o von Willebrand disease

von Willebrand Disease

- vWF made by endothelial cells and megakaryocytes

- needed for platelet adhesion to subendothelial collagen via interaction with plt glycoprotein Ib

- relatively common disorder, several types:

o type 1: reduced amount vWF, autosomal dominant, most common form, clinically mild

o type 2: reduced amount intermediate and large vWF multimers (active forms of vWF), autosomal

dominant

o type 3: reduced amount vWF, autosomal recessive, uncommon, severe

- levels of factor VII often reduced because vWF stabilises factor VII in circulation

o therefore patients have defects in platelet function and coagulation pathway

o prolonged bleeding time (despite normal plt count) and prolonged PTT

- commonly presents with spontaneous bleeding from mucous membranes, excess bleeding from wounds and

menorrhagia

- except in type 3, FVIII levels only moderately depressed so symptoms of haemophilia uncommon (bleeding into

joints)

Factor VIII Deficiency (Haemophilia A)

- X-linked recessive (affects males and homozygous females)

- reduced amount and activity of factor VIII

- clinical features only in severe deficiency (levels <1% of normal)

- mild-moderate deficiency (1-50%) asymptomatic, but may have excessive post-traumatic bleeding

- variable deficiency is due to different types of mutations in factor VIII gene

- clinically:

o massive haemorrhage after trauma or operations

o spontaneous haemorrhages in regions of body subject to trauma (joints – haemarthroses), which lead to

progressive, crippling deformities

o absence of petechiae

o prolonged PTT and normal bleeding time

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- diagnosis: factor VIII assay, also antenatal diagnosis

- treatment: recombinant factor VIII or factor VIII concentrates

- previously high rate of HIV before blood screened and heat-treated

Factor IX Deficiency (Haemophilia B, Christmas Disease)

- x-linked recessive

- clinically indistinguishable from Haemophilia A

- assay of factor IX levels

Disseminated Intravascular Coagulation

- acute, subacute or chronic thrombohaemorrhagic disorder occurring as a secondary complication of a number of

diseases

- activation of coagulation sequence – formation of microthrombi throughout microcirculation

- causes consumption of platelets, fibrin and coagulation factors, and secondary activation of fibrinolytic

mechanisms

- clinically:

o signs and symptoms of infarction due to microthrombi

o haemorrhagic diathesis from activation of fibrinolytic mechanisms and depletion of haemostatic elements

Major Disorders Associated with Disseminated Intravascular Coagulation

Obstetric Complications

Abruptio placentae, Retained dead fetus, Septic abortion, Amniotic fluid embolism, Toxemia

Infections

Gram-negative sepsis, Meningococcemia, RMSF, Histoplasmosis, Aspergillosis, Malaria

Neoplasms

Carcinomas of pancreas, prostate, lung, stomach; Acute promyelocytic leukaemia

Massive Tissue Injury

Traumatic, Burns, Extensive surgery

Miscellaneous

Acute intravascular haemolysis, snakebite, giant haemangioma, shock, heat stroke, vasculitis, AAA, liver

disease

Pathogenesis:

- triggered by two mechanisms:

o release of tissue factor or thromboplastic substances:

� tissue factor or thromboplastic substances from placenta in obstetric complications, granules of

leukaemic cells, mucus from adenocarcinomas

• gram negative sepsis – endotoxins activate monocytes which release IL1 and TNF

which increase tissue factor expression on endothelial cell membranes while decreasing

thrombomodulin expression

o results in both activation of clotting system and inhibition of coagulation

control

o widespread endothelial cell injury:

� initiates DIC by causing tissue factor release from endothelial cells, promoting platelet

aggregation and by activating the intrinsic coagulation pathway by exposing subendothelial

connective tissue

� can occur through antigen-antibody complex deposition (SLE), temperature extremes

(heatstroke, burns) or infections (meningococci, rickettsiae)

Morphology:

- microthrombi with infarctions and sometimes haemorrhages found in many organs and tissues

o kidneys: thrombi in renal glomeruli – microinfarcts or renal cortical necrosis

o lungs: microthrombi in alveolar capillaries, may resemble ARDS

o brain: microinfarcts and haemorrhages

o adrenals: massive haemorrhages - Waterhouse-Friderichsen synd in meningococcaemia

o placenta: widespread thrombi with atrophy

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Clinically:

- ~50% in obstetrics, ~33% in carcinomatosis, the rest mainly sepsis and trauma

- onset fulminant (endotoxic shock or amniotic fluid embolism) – usually bleeding, or insidious (carcinomatosis,

retained dead fetus) – usually thrombotic

- many clinical manifestations:

o microangiopathic haemolytic anaemia from widespread microvascular occlusion

o respiratory symptoms (dyspnoea, cyanosis, resp distress)

o neurological (seizures, coma)

o oliguria, ARF

o circulatory failure and shock

- treatment depends on clinical picture: treat underlying cause, heparin and antithrombin III or coagulants such as

FFP

Blood Types

- rbcs contain blood group antigens called agglutinogens

ABO system:

- A and B antigens inherited as mendelian dominants

- 4 blood groups

Genotypes Blood Types Agglutinogens Agglutinins

OO O (47%) - Anti-A and Anti-B

OA or AA A (41%) A Anti-B

OB or BB B (9%) B Anti-A

AB AB (3%) A and B -

- when type A agglutinogen not present, antibodies called anti-A agglutinins develop

- when type B agglutinogen not present, antibodies called anti-B agglutinins develop

- type AB contains both A and B agglutinogens but no agglutinins

- origin of agglutinins: gamma globulins, IgG and IgM, produced due to small amounts of type A and B antigens

enter body in food, bacteria, and other ways, and initiate development of anti-A and anti-B agglutinins

- agglutination process in transfusion reactions: if anti-A or anti-B plasma agglutinins are mixed with red blood cells

that contain A or B agglutinogens, the red cells agglutinate as a result of agglutinins' attaching themselves to rbcs –

causes cells to clump, plug small blood vessels, or be attacked by WBCs causing haemolysis

o either immediate haemolysis (less common) – need high titer of Abs

o or delayed haemolysis

- O negative - universal donors, AB positive - universal recipients

Rh blood types:

- unlike ABO system, Rh system spontaneous agglutinins almost never occur; instead, must first be massively

exposed to Rh antigen, such as by transfusion of blood containing Rh antigen

- six common types of Rh antigens - C, D, E, c, d, and e (have one of each of three pairs)

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- 85% white people have type D antigen, called Rh positive

- Anti-Rh Agglutinins form if Rh-negative person injected with Rh-positive blood, sensitized for next exposure –

develop anti-Rh Abs in 2-4 weeks that cause a mild delayed transfusion reaction – subsequent exposure would

cause severe reaction

Erythroblastosis Fetalis (Haemolytic Disease of the Newborn):

- agglutination and phagocytosis of fetus’s rbcs

- usually mother Rh negative and father Rh positive

- baby inherits Rh-positive, mother develops anti-Rh agglutins from exposure to fetus’s RhD

- mothers agglutinins diffuse through the placenta into fetus and cause agglutination

- causes jaundice with kernicterus, severe anaemia

- treatment: replace neonate's blood with Rh-negative blood

- prevention: anti-D antibody given to Rh-negative mother at 28-30/40

Transfusion Reactions:

- transfusion reaction likely to occur if red blood cells of the donor blood are agglutinated

- rare that transfused blood causes agglutination of recipient's cells, because plasma portion of donor blood

immediately diluted

- either immediate haemolysis resulting from haemolysins or later haemolysis resulting from phagocytosis of

agglutinated cells

- acute: fever, tachycardia, hypotension, bleeding, haemoglobinuria, hyperbilirubinaemia, chest and back pain

- haemoglobin released from red cells converted by phagocytes into bilirubin – jaundice

- can cause renal failure few mins to few hours after transfusion. 3 causes:

o Ag-Ab reaction releases toxic substances from haemolyzing blood cause renal vasoconstriction

o loss of circulating red cells, along with production of toxic substances from haemolyzed cells and from

immune reaction, often causes circulatory shock

o if total amount of free haemoglobin released into circulating blood is greater than quantity that can bind

with haptoglobin, much of excess leaks through glomerular membranes into kidney tubules - haemoglobin

precipitates and blocks kidney tubules

Other antigens:

MNSs, Lutheran, Kell, Kidd, Duffy, H

White Blood Cells

- disorders are deficiencies or proliferations (reactive or neoplastic)

Leukopenia

Neutropenia

- clinically significant <1000cells/mm3, counts <200 cells/mm

3 = agranulocytosis

- clinically neutrophil half life 6-7 hrs so insults that impair granulopoiesis quickly produce neutropenia

- mechanisms:

o inadequate or ineffective granulopoiesis

� suppression of myeloid stem cells (aplastic anaemia, infiltrative marrow disorders – tumours,

granulomatous disease)

� suppression of committed granulocytic precursors (exposure to some drugs)

� disease states characterised by ineffective granulopoiesis (megaloblastic anaemia,

myelodysplastic syndromes)

� rare inherited conditions (Kostmann syndrome)

o increased removal or destruction of neutrophils

� injury to neutrophils by immunologic disorders (SLE) or drug exposures

� splenic sequestration

� increased peripheral utilization in bacterial, fungal, rickettsial infections

o most significant neutropenias are drug induced:

� dose-related: predictable fashion (chemo drugs – alkylating agents, antimetabolites)

� idiosyncratic and unpredictable (aminopyrine, chloramphenicol, sulfonamides, chlorpromazine,

thiouracil, phenylbutazone)

- morphology:

o marrow alterations depend if only granulocytes affected or if all cell types affected

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� marrow hypercellularity (increased granulocytic precursors)

• increased destruction of mature neutrophils

• ineffective granulopoiesis (megaloblastic anaemia, myelodysplastic)

� marrow hypocellularity

• neutropenia due to drugs that suppress granulocyte progenitor cells

- clinically:

o related to intercurrent bacterial or fungal infections

� malaise, fever, chills, weakness, fatigability

� ulcerating necrotizing lesions of gingiva, buccal mucosa or pharynx

- prognosis:

o infections often fulminant – need broad spectrum Abs at first sign of infection

o granulocyte-colony stimulating factor decreases duration and severity after chemo

Reactive (Inflammatory) Proliferations of White Blood Cells and Nodes

Leukocytosis

- commonly in variety of inflammatory states

- particular type of leukocyte affected depends on underlying cause:

o polymorphonuclear leukocytosis (neutrophilic granulocytosis, neutrophilia)

� acute inflammation associated with infection or tissue necrosis

� sepsis or severe inflammatory disorders cause neutrophils to develop toxic changes

• abnormally coarse, dark neutrophilic granules (toxic granulations)

• blue cytoplasmic patches of dilated ER (Dohle bodies)

• cytoplasmic vacuoles

o eosinophilic leukocytosis (eosinophilia)

� allergic disorders (asthma, hay fever, allergic skin diseases)

� parasitic infections

� drug reactions

� some malignancies (Hodgkin lymphoma)

� collagen vascular disorders and vasculitides

� atheroembolic disease (transiently)

o basophilic leukocytosis

� rare, suggests underlying myeloproliferative disease (eg CML)

o monocytosis

� chronic infections (Tb, bacterial endocarditis, malaria)

� collagen vascular diseases (SLE)

� inflammatory bowel disease

o lymphocytosis

� accompanies monocytosis in many disorders associated with chronic immunologic stimulation

(Tb), viral infections (Hep A, CMV, EBV), Bordetella pertussis

Pathogenesis:

- elevation of circulating neutrophil counts (most common form of leukocytosis) occurs by various mechanisms:

o expansion of marrow neutrophilic progenitor cell and storage pools

� hours to days after elevated colony-stimulating factors released from marrow

� stimulants of colony stimulating factor production: IL1, TNF (eg in infectious and inflammatory

disorders)

o increased release of mature neutrophils from bone marrow storage pool rapidly after elevations in IL1 and

TNF

o increased demargination of peripheral blood neutrophils in acute stress, or with steroids

o decreased extravastation of neutrophils into tissues with steroids

- other factors cause different forms of leukocytosis

o IL5 causes eosinophilic leukocytosis

o C-kit ligand and IL7 induce lymphopoiesis

- distinguishing reactive leukocytosis from neoplastic (leukaemia) problematic in two settings:

o childhood acute viral infections (atypical lymphocytes can simulate leukaemia

o severe inflammatory states – immature granulocytes sometimes appear in blood and simulate

myelogenous leukaemia (leukemoid reaction)

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Acute Nonspecific Lymphadenitis

- localized or systemic:

o localized – commonly caused by direct microbiologic drainage (cervical area from dental or tonsil

infections)

o systemic – associated with bacteremia and viral infections, esp children

- affected nodes enlarged, tender, fluctuant if abscess formation, overlying skin red, +/- sinuses

Chronic Nonspecific Lymphadenitis

3 patterns:

- follicular hyperplasia

o caused by inflammatory processes that activate B cells

� RA, toxoplasmosis, early stages of HIV

- paracortical lymphoid hyperplasia

o due to activated T cells

� immunologic reactions induced by drugs (phenytoin) and acute viral infections (EBV)

- sinus histiocytosis (reticular hyperplasia)

o infiltration of histiocytes (macrophages)

� non-specific, often in LNs draining epithelial cancers

Neoplastic Proliferations of White Blood Cells

- 3 broad categories:

o lymphoid neoplasms

� tumours of B-cell, T-cell or NK cell origin

o myeloid neoplasms

� originate from transformed haematopoietic stem cells that produce myeloid lineage cells

(erythroid, granulocytic, thrombocytic)

• acute myelogenous leukemias

• myelodysplastic syndromes

• chronic myeloproliferative disorders

o histiocytoses

� lesions of histiocytes, including Langerhans cells

Aetiologic and Pathogenetic Factors in White Blood Cell Neoplasia

Chromosomal Translocations and Oncogenes

- can cause inappropriate expression of normal proteins or synthesis of novel oncoproteins

- some translocations specific to one tumour type, others occur in several neoplasms

Inherited Genetic Factors

- genetic disease promote genomic instability (Downs and NF1 have increased risk of leukaemia)

Viruses and Environmental Agents

- HTLV-1 – T cell leukaemia

- EBV – lymphomas

- HHV8 – B cell lymphomas

- environmental agents that cause chronic immune stimulation predispose to lymphoid neoplasm

o H. pylori – gastric lymphoma; gluten-sensitive enteropathy – Tcell lymphoma

Iatrogenic Factors

- radiotherapy, chemotherapy increases the risk of wbc neoplasms

o AML, myelodysplastic syndrome, lymphoma

Lymphoid Neoplasms

- diagnosis required biopsy of LNs or other involved tissues

- all lymphoid neoplasms come from single transformed cell – monoclonal

- 85% B cell origin

- tend to disrupt normal immune regulatory mechanisms

- neoplastic B and T cells circulate widely but tend to home in and grow where normally reside

- five broad categories, based on their cell of origin/immunophenotype:

o precursor B-cell neoplasms (immature B cells)

o peripheral B-cell neoplasms (mature B cells)

o precursor T-cell neoplasms (immature T cells)

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o peripheral T-cell and NK-cell neoplasms (neoplasms of mature T and NK cells)

o Hodgkin lymphoma (neoplasms of Reed-Sternberg cells and variants)

- leukaemia: widespread involvement of BM, with large numbers of circulating tumour cells

- lymphoma: proliferations involving discrete tissue masses (eg in LNs, spleen or extranodal tissue); two broad

categories:

o Hodgkin lymphoma

o Non-Hodgkin lymphoma

- plasma cell neoplasms: tumours composed of terminally differentiated B cells

Precursor B-cell and T-cell Neoplasms

Acute Lymphoblastic Leukaemia/Lymphoma (ALL):

- composed by immature, precursor B (pre-B) or precursor T (pre-T) lymphocytes (lymphoblasts)

o 85% pre-B tumours childhood acute leukaemias involving marrow and blood

o less common pre-T ALLs in adolescent boys, involve thymus (mediastinal mass)

o 90% of ALL have chromosomal changes

- clinically: ALL and AML similar

o abrupt stormy onset in days-weeks

o symptoms related to depressed marrow function (anaemia, infections, bleeding )

o bone pain

o generalized lymphadenopathy, splenomegaly, hepatomegaly (testes common in ALL)

o CNS – headache, vomiting, nerve palsies

- good prognosis

Peripheral B-cell Neoplasms

Chronic Lymphocytic Leukaemia/Small Lymphocytic Lymphoma:

- CLL and SLL on differ by degree of peripheral lymphocytosis

- prolymphocytes

- involves marrow, spleen, liver

- CLL most common adult leukaemia (lymphocyte count >1000cells/mm3)

- clinically:

o median age 60, M:F 2:1

o fatigue, weight loss, anorexia

o generalized lymphadenopathy, hepatosplenomegaly

o lymphocytosis up to 200,000 cells/mm3

o immune abnormalities – hypogammaglobulinaemia, autoAbs against rbcs or plts

- worse prognosis

Follicular Lymphoma:

- most common form NHL

- proliferations centrocytes and centroblasts

- involves spleen, liver, marrow

- clinically:

o painless, generalized lymphadenopathy in middle age, waxing-waning course

o not curable, median survival 7-9 years

o 30-50% transform to diffuse large B-cell lymphoma – poor prognosis

Diffuse Large B-cell Lymphoma:

- makes up 20% NHL and 60% aggressive lymphoid neoplasms

- 2 subtypes occur in immunodeficiency

- clinically:

o median age 60

o rapidly enlarging symptomatic mass at nodal or extranodal site (GI, skin, bone, brain)

o aggressive, rapidly fatal untreated but good rates of remission with chemo

Burkitt Lymphoma:

- 3 different settings: African (endemic) BL, Sporadic BL, aggressive subset in HIV

- comprise of relatively mature B cells

- African tumours infected with EBV

- clinically:

o childhood or young adult

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o rapidly growing masses at extranodal sites (African in mandible, nonendemic often ileocecal or

peritoneal)

- aggressive but responds well to chemo – may be cured

Plasma Cell Neoplasms and Related Disorders:

- neoplasms of terminally differentiated B cells

- expansion of a single clone of Ig-secreting plasma cells with increase in serum levels of a single Hb or its

fragments (monoclonal gammopathy)

- sometimes only light or heavy chains produced (free light chain in urine – Bence Jones protein)

- clinically:

o Multiple myeloma (plasma cell myeloma)

o Solitary plasmacytoma

o Monoclonal gammopathy of undetermined significance

o Waldenstrom macroglobulinaemia

o Primary or lymphocyte-associated amyloidosis

o Mantle Cell Lymphoma

o Marginal Zone Lymphoma

o Hairy Cell Leukaemia

- Multiple Myeloma:

o most common of malignant gammopathies

o plasma cell neoplasm of older adults

o destructive bony lesions at multiples sites

o tumours secrete free light chains, cause renal disease and sometimes cause amyloidosis

o tumour cells produce cytokines including MIP1α and RANKL that are osteoclast-activating factors and

contribute to bony destruction – vertebrae, ribs, skull, pelvis, femur – sharply punched out

o generalized osteoporosis

o renal disease due to:

� protein casts in tubules

� metastatic calcification due to hypercalcaemia

� pyelonephritis due to risk of bacterial infections

� amyloid deposition in glomeruli

� lightchain deposition in glomeruli

� interstitial infiltrates of abnormal plasma cells or chronic inflammatory cells

o in advanced disease plasma cells infiltrate spleen, liver, LNs, skin, nerve roots

o Bence-Jones protein (Ig light chain) on urine electrophoresis

o high levels of a single Ig in serum (M protein ‘spike’) (usually IgG or IgA)

o other Ig levels decreased

o clinically:

� peak age 50-60

� clinical features due to:

• organ infiltration

• excess Ig production

• suppression of normal humoral immunity

� bone infiltration, bone pain, pathologic fractures

• secondary hypercalcaemia causes renal disease, polyuria, confusion, lethargy, weakness,

constipation

� recurrent bacterial infections

• decreased production of normal Igs

� hyperviscosity syndrome

• excessive M protein production and aggregation

� renal insufficiency

• multifactorial, BJ proteinuria most important – toxic to tubules

� extensive bone marrow involvement

• normocytic, normochromic anaemia and moderate pancytopenia

o prognosis: depends on stage/level of Bence Jones/number of bony lesions

o chemo induces remission in 50-70% but median survival only 3 years

o causes of death most often infection and renal failure

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Peripheral T-cell and NK cell Neoplasms

- cells resemble normal T or NK cells

Peripheral T-cell Lymphoma

- generalised lymphadenopathy, sometimes eosinophilia, pruritis, fever and weight loss

- poor prognosis

Anaplastic Large Cell Lymphoma:

- disseminated disease, good prognosis if have ALK gene rearrangement

Adult T-Cell Leukaemia/Lymphoma:

- in patient infected with HTLV-1 (human T-cell leukaemia virus type-1), cells express CD4

- skin involvement, generalized lymphadenopathy, hepatosplenomegaly, peripheral blood lymphocytosis,

hypercalcaemia

- aggressive disease, refractory to treatment, median survival 8 months

Mycosis Fungoides and Sezary Syndrome:

- tumours of T cells that home to skin (cutaneous T cell lymphomas), composed of CD4+ T cells

Large Granular Lymphocytic Leukaemia:

- CD8+ cells - lymphocytosis, splenomegaly, neutropenia, anaemia

Hodgkin Lymphoma:

- one of most common malignancies in young adults, average age onset 32

- presence of neoplastic giant cells called Reed-Sternberg cells

- often localized to single group LNs - painless enlargement, extranodal involvement uncommon

- associated with EBV

- tumour burden rather than stage is prognostic indicator

- complications of therapy: risk of second cancer (NHL, AML, myelodysplastic or solid organ)

Myeloid Neoplasms

- common origin from progenitor cells that usually give rise to cells of myeloid series (erythrocytes, granulocytes,

monocytes, platelets)

- almost always involve marrow

- lesser involvement of spleen, liver, LNs

- 3 forms:

o acute myelogenous leukaemia

� marrow accumulation of immature myeloid cells

o myelodysplastic syndromes

� ineffective haematopoiesis and cytopenias

o chronic myeloproliferative disorders

� increased production of terminally differentiated myeloid cells

Acute Myelogenous Leukaemia:

- heterogeneous group of disorders, undifferentiated immature myeloid progenitor cells (blasts) accumulate in

marrow and displace normal cells causing haematopoietic failure

- assoc with acquired (or rarely inherited) genetic alterations that inhibit terminal differentiation

- variable number of leukaemia cells in circulation

o diagnosis based on >20% myeloid blasts in marrow

- 50-70% have karyotypic changes

- AML can arise:

o de novo in patients with no risk factors and normal karyotype

o following myelodysplastic syndrome or after chemo/radiation

o after treatment with drugs that inhibit enzyme topoisomerase II

o with certain translocations

- clinically:

o makes up 20% childhood leukaemias

o M>F, peak age 15-39, features similar to ALL

o weeks-months: anaemia, neutropenia, thrombocytopenia (fatigue, fever, bleeding)

o petechiae, ecchymoses, bleeding gingival/GI/GU; opportunisitic infection

o procoagulants released by leukaemic cells can cause DIC

o mild lymphadenopathy and organomegaly

o CNS less common in AML

- prognosis variable: 60% remission with chemo, but only 20% disease free at 5 years

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Myelodysplastic Syndromes:

- group of clonal stem cell disorders with ineffective haematopoiesis

- risk of transformation to AML (highest risk in therapy-related MDS)

- marrow partially/wholly replaced by clones of mutent multipotent stem cell that retains it capacity to differentiate

into rbcs/granulocytes/platelets but ineffective and disordered

- marrow hypercellular or normocellular

- blood shows pancytopenia

- arises in 2 settings:

o idiopathic or primary MDS (>age 50)

o therapy-related MDS (2-8 yrs post myelosuppressive chemo or radiotherapy)

- pathogenesis unknown, happens after stem cell damage and chromosomal abnormalities

- clinically: half asymptomatic, found incidentally, symptoms due to cytopenias

- prognosis: median survival 9-29 months (worse prognosis if therapy-related, increased numbers of blasts, multiple

clonal chromosomal abnormalities or severe thrombocytopenia

Chronic Myeloproliferative Disorders:

- 4 chronic MPDs:

o chronic myelogenous leukaemia (CML)

o polycythaemia vera

o essential thrombocytosis

o myelofibrosis with myeloid metaplasia

- in last 3 the target of neoplastic transformation is a multipotent progenitor cell capable of giving rise to mature

erythrocytes, platelets, granulocytes and monocytes

- in CML the target is a pluripotent stem cell that can give rise to lymphoid and myeloid cells

- chronic MPDs are similar to AML – neoplastic cells flood marrow and suppress normal cells, however unlike

AML terminal differentiation is initially unaffected

- this causes marrow hypercellularity, increased haematopoiesis and often elevated cell counts

- features common to all 4 chronic MPDs:

o neoplastic stem cells home to haematopoietic organs, esp spleen and extramedullary haematopoiesis

causes splenomegaly

o a terminal phase with marrow fibrosis and cytopenias

o progression over time to acute leukaemia (only CML)

- MPDs overlap with each other and reactive conditions – diagnosis by labs esp cytogenetics

Chronic Myelogenous Leukaemia:

- neoplasm pleuripotent haematopoietic stem cell causing proliferation granulocytic progenitors

- distinguished from other MPDs by t(9;22) Philadelphia chromosome (BCR-ABL fusion gene)

- high levels granulocytes (mixture neutrophils, metamyelocytes, myelocytes)

- also eosinophilia, basophilia, thrombocytosis

- marked splenomegaly – can cause infarction

- clinically:

o 25-60 years

o insidious onset of fatigue, weakness, weight loss, anorexia due to anaemia

o symptoms related to splenomegaly or infarction

o 3 years stable phase, then 50% develop accelerated phase with worsening anaemia and thrombocytopenia,

in 6-12 months terminated in acute leukaemia (blast crisis)

o other 50% go straight to blast crisis with no intermediate stage

o less commonly progress to diffuse marrow fibrosis

- curable by bone marrow transplant during stable phase

- if can’t have transplant use Gleevec – BCR-ABL kinase inhibitor

Polycythaemia Vera:

- transformed multipotent myeloid stem cell

- increased proliferation and production of erythroid, granulocytic and megakaryocytic elements

- causes erythrocytosis (polycythaemia), granulocytosis, thrombocytosis

- increased rbc mass responsible for most symptoms

- early in disease: BM hypercellularity (all lineages), basophilia and neutrophilia, giant platelets and megakaryocyte

fragments, mild organomegaly

- late in disease: marrow fibrosis leading to extramedullary haematopoiesis – organomegaly

- transformation to AML in 2-15%

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- Hb 140-280, Hct >60%, increased WCC and platelets, BCR-ABL fusion genes absent

- clinically:

o insidious onset late middle age

o erythrocytosis – incr rbc mass and incr total blood volume causes abnormal flow, vascular distension,

vascular stasis – plethora, cyanosis, hypertension

o basophilia – histamine release increases risk of GI ulcers, pruritis

o high cell turnover – hyperuricaemia and gout

o platelet dysfunction – with abnormal flow increase risk of bleeding and thrombosis

- without treatment, death from thrombosis or bleeding in months

- with phlebotomy median survival 10 years

Essential Thrombocytosis:

- MPD arising in pluripotent stem cell, but increased proliferation confined to megakaryocytes

- dysfunction of platelets from neoplastic clones cause bleeding and thrombosis

- thrombocytosis, abnormally large platelets, mild leukocytosis

- extramedullary haematopoiesis produces mild organomegaly in 50%

- uncommonly evolves to spent phase of marrow fibrosis or transforms to AML

- clinically:

o usually after age 60

o thrombosis and haemorrhage

o erythromelalgia (throbbing, burning of hands/feet - occlusion small arterioles by plts)

o indolent course, long asymptomatic periods, median survival 12-15 years

Primary Myelofibrosis:

- marrow fibrosis with myeloid metaplasia from a transformed multipotent myeloid stem cell

- extensive collagen deposition in marrow displaces haematopoietic cells

- leads to extensive extramedullary haematopoiesis in spleen, liver, sometimes LNs

- fibrosis due to inappropriate release of platelet-derived growth factor and TGF-β from neoplastic megakaryocytes

- pancytopenia, symptoms of anaemia, splenomegaly, gout in >60 yrs

- prognosis: median survival 1-5yrs – infection, thrombosis, bleeding, transformation to AML

Langerhans Cell Histiocytosis

- clonal proliferation of a subtype of antigen-presenting dendritic cell

- aka histiocytosis X

- 3 patterns of disease:

o multifocal multisystem – aggressive systemic disorder where Langerhans cell infiltrate and proliferate in

the skin, spleen, lung, liver, BM

� anaemia and bone lesions

� < age 2, fatal if untreated

o unifocal – erosive, expanding accumulation of Langerhans cells in bones

� asymptomatic or painful, may have pathological fractures

� in children/young adults, usually male

o multifocal unisystem – children, fever and diffuse eruptions esp scalp and ear canals

� frequent OM, mastoiditis, URTIs, bone lesions, lymphadenopathy, hepatosplenomegaly

� 50% involve pituitary stalk causing DI

Splenomegaly

- often a feature of haematolymphoid disorders

- hypersplenism in a minority with splenomegaly (splenomegaly, reduction in one or more cellular elements of

blood due to sequestration and splenic macrophage lysis, correction of cytopenias after splenectomy)

Disorders Associated with Splenomegaly

I. Infections

Non-specific splenitis of various blood-borne infections (particularly infective endocarditis) infectious mononucleosis

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Tuberculosis, Typhoid fever, Brucellosis, CMV, Syphilis, Malaria, Histoplasmosis, Toxoplasmosis, Trypanosomiasis,

Schistosomiasis, Leishmaniasis, Echinococcosis

II. Congestive States Related to Portal Hypertension

Cirrhosis, portal or splenic vein thrombosis, RHF

III. Lymphohematogenous Disorders

Lymphoma, myeloma, myeloproliferative disorders, haemolytic anaemia, TTP

IV. Immunologic-Inflammatory Conditions

RA, SLE

V. Storage Diseases

Gaucher disease, Niemann-Pick disease, Mucopolysaccharidoses

VI. Miscellaneous

Amyloidosis, primary neoplasms and cysts, secondary neoplasms