MLAB 1415- Hematology

Keri Brophy-Martinez

Chapter 9: Iron Metabolism and Hypochromic Anemias

Iron Metabolism

Primary function Oxygen transport and storage

Distribution Types of iron-containing compounds

• Functional, assisting in enzymatic and metabolic functions

• Transportation or storage Location

• RBCs- majority here

• Macrophages of spleen& liver- where destruction of RBC occurs, liberating iron

• Hepatocytes and enterocytes- storage of iron

Iron Metabolism

Iron absorption and storage is influenced by: The amount and type of available iron in the diet

• Is it a nutritional deficiency Incomplete absorption due to GI tract problems Current iron stores Increased demand (pregnancy, the growth years) Excessive loss due to acute or chronic hemorrhage

• menstrual period for women of childbearing years, GI bleeding for men

Forms of Iron

NonhemeIonic or ferricFound in vegetables and whole grains

HemeFound in red meatsEasily absorbed

Iron Metabolism

Transport Transferrin

• Transports iron to bone marrow to be used in hgb synthesis

• Synthesized in the liver Storage

Primarily in the liver Ferritin

• Soluble iron, quick release for heme synthesis Hemosiderin

• Partially degraded iron, slow release

Iron Balance

Loss of ironSecretions of urine, bile , sweat and

exfoliation of intestinal epithelial cells of GI tract

Approx. 1 mg/ day Regulation of iron

Delicate balance between loss and absorption

Laboratory Assessment of Iron

Serum iron Total iron binding capacity (TIBC) Percent saturation Serum ferritin

Clinical Syndromes of Iron Metabolism

Iron Deficiency Anemia (IDA)AKA Sideropenic anemiaThis is the most common form of

anemia.IDA occurs when the iron stores

in the body are inadequate to preserve homeostasis.

Causes of IDA

Dietary Blood Loss Hemodialysis Malabsorption

3 Stages of IDA

Stage 1• Decrease in storage iron (ferritin decrease)• No anemia• RBC morphology normal• RDW can be elevated

Stage 2• Decrease in iron for erythropoiesis• No anemia or hypochromia• RBC slightly microcytic

Stage 3 • Decrease in Blood Hgb• Decrease in peripheral tissue oxygen delivery• All lab tests abnormal• Microcytic, hypochromic anemia

Clinical Features of IDA

SOB Lethargy Pallor Gastritis Pica Koilonychia

IDA: Lab features

Decreased RBC, Hgb, Hct, MCV,

MCH, MCHC

Normal to decreased Retic

Peripheral blood smear microcytic-hypochromic Targets, elliptocytes,

teardrops If IDA is caused by

bleeding, leukocytosis and thrombocytosis are possible.

IDA: Lab Findings

Bone marrow Decrease in stainable iron Decrease in erythroid hyperplasia M:E ratio decreased

Chemistry Decrease in serum iron and ferritin Increased TIBC

Anemia of Chronic Disease (ACD)

Anemia that occurs in patients with chronic infections, chronic inflammatory disorders, trauma, organ failure or neoplasms

Occurs due to biochemical changes during inflammation

Hallmark is normal iron stores but low serum iron

Anemia of Chronic Disease

MechanismsBlock in release of iron from

macrophages due to increased cytokines

Cytokine inhibition of EPO productionCytokine inhibition of erythropoiesisShortened erythrocyte survival

ACD: Lab Features

Typical lab findings Decreased

• RBC, Hgb, Hct, MCV, MCH, serum iron Increased

• ferritin Normal

• MCHC Normal to decreased

• Retic, TIBC Peripheral blood smear

• normocytic-normochromic• Targets, elliptocytes, teardrops

Bone marrow• M:E ratio increased

Anemia’s Associated with Abnormal Heme Synthesis

Sideroblastic Anemia Lead Poisoning Porphyrias

Sideroblastic Anemia (SA)

First step in heme synthesis is affected

Characterized by:Increase in total body ironPresence of ringed sideroblasts in

bone marrowHypochromic anemia

Sideroblastic anemia

Classification Hereditary Acquired

• 2 Forms• Idiopathic • Secondary type

• Certain therapeutic drugs• Chronic transfusions (for aplastic anemia, leukemia,

thalassemia)• Alcoholism and food fads• Use of iron utensils or increased iron in water

.

Sideroblastic anemia

MechanismAdequate iron but it can not be

incorporated into hgb synthesis.Iron enters mitochrondria of

metarubricyte, but accumulates leading to formation of ringed sideroblasts

Eventually, mitochrondria rupture

Lead poisoning

Lead interferes with iron storage in the mitochondria

Lead damages the activity of enzymes used for heme synthesis

Basophilic stippling pronounced

Lead Poisoning

Lab features of SA

Peripheral blood Pappenheimer bodies Hypochromic,

normochromic RBCs Normal to increased

platelets Chemistry

Increased serum iron, ferritin

Hemochromatosis

Condition caused by increased iron absorption which deposits in vital organs such as the liver, spleen and pancreas which then becomes fibrotic

Hyperpigmentation of skin

Therapy consists of iron removal by therapeutic phlebotomy or chelation

Porphyrias

Excessive production of porphyrins in the bone marrow (or liver) Rare disease caused by accumulation of

porphyrins in developing RBC’s Defect in one or more of the enzymes in

heme synthesis pathway Characterized by dermal photosensitivity and

rash caused by the sun. The original werewolf was probably a person with erythropoietic porphyria.

References

• Harmening, D. M. (2009). Clinical Hematology and Fundamentals of Hemostasis. Philadelphia: F.A Davis.

• McKenzie, S. B., & Williams, J. L. (2010). Clinical Laboratory Hematology . Upper Saddle River: Pearson Education, Inc.

• http://healthmap.wordpress.com/2008/11/