HEREDITARY HAEMOLYTIC ANAEMIAS

BY

DR. KAMAL E. HIGGY

CONSULTANT HAEMATOLOGIST

HEREDITARY SPHEROCYTOSIS

HEREDITARY HAEMOLYTIC ANAEMIA

MEMBRANE DEFECTS

* Hereditary Spherocytosis * Hereditary Elliptocytosis * Hereditary Stomatocytosis etc….

HEREDITARY HAEMOLYTIC ANAEMIA

METABOLIC DEFECTS: Deficiency of:

* Glucose-6-phosphate dehydrogenase * Pyruvate kinase * Triose phosphate isomerase * Pyrimidine-5-nucleotidase * Glutathione synthetase etc….

HEREDITARY HAEMOLYTIC ANAEMIA

HAEMOGLOBIN DEFECTS: * Defective synthesis

e.g. Thalassaemia (Alpha or Beta)

* Abnormal variants

e.g. Hb S, Hb C, Unstable Hb

GENETIC ABNORMALITIESOF

THE RED CELL MEMBRANE

Hereditary Spherocytosis Hereditary Elliptocytosis Hereditary Stomatocytosis Hydrocytosis (high MCV, low MCHC) Xerocytosis (low MCV, high MCHC shrunken RBCs

due to K loss) Acanthocytosis – Abeta-lipoproteinaemia

GENETIC ABNORMALITIES OF THE RED CELL MEMBRANE

HEREDITARY SPHEROCYTOSIS (HS)NAME Electrophoretic

Band*Molecular

weight (kd)

Number of

molecules /RBC

(x 105 )

Location / function ChromosomalAssignment

Gene cloned

αSpectrin

β

1 240 22

CS: form heterodimers, tetramers

1 q22 – 1 q25Yes

2 220 Yes

Actin 5 42 5 Cs: forms protofilaments of 10-13 monomers

7 pter – q22 Yes

‘ Band ‘ 4.1 78 2 Crosslinks spectrin heterodimers

1 p32 – 1 pter Yes

Ankyrin 2.1 210 1 Links spectrin to band 3

‘ Band ‘ 3 95 10 IMP: anion transport: links to ankyrin

Glycophorin A

PASI, 229 4 IMP: sialoglycoprotein 4 q28 Yes

IMP = integral membrane protein CS = cytoskeleton * as currently numbered on SDS – gels

PATHOGENESIS OF

HEREDITARY SPHEROCYTOSIS (HS)

? Spectrin

genes

? Gene for

other membrane protein

Abnormal

spectrin

Decreased

Synthesis

of spectrin

Decreased

binding of

spectrin

Decreased

spectrin in

membrane

Spherocytes

OF

Glucose

requirement

Decreased

deformability

HEREDITARY SPHEROCYTOSIS (HS)

DEFINITION:

A congenital disorder which is characterized by:

* spherocytes

* increased osmotic fragility

* autosomal dominant inheritance ( ! recessive )

* beneficial response to splenectomy

HEREDITARY SPHEROCYTOSIS (HS)

The diagnosis of HS is not always easy since:

* The degree of spherocytosis is variable

* The changes in osmotic fragility are not always clear cut

* Sporadic cases can occur

* Other haemolytic anaemias may respond to splenectomy

HEREDITARY SPHEROCYTOSIS (HS)

Role of spleen: * Results post splenectomy - Decrease in the rate of haemolysis (ameliorates the degree of anaemia) - Decrease in the number of spherocytes (but can not cure the red cell abnormality) * Spleen is the major site of red cell destruction * RBCs retained for long time in the splenic pulp as a result of decreased deformability

+ Unfavorable environmental conditions in the splenic pulp (acid pH & decreased glucose)

Failure of the cation pump

Loss of water

Loss of RBCs discoid shape

Vicious circle

HEREDITARY SPHEROCYTOSIS (HS)

Clinical Manifestations:• Most of the cases present in childhood or as teenagers

• HS has been rarely diagnosed at:

* Neonatal period (persistent jaundice)

* The age of 60 (asymptomatic)

• The disease has a wide spectrum of severity

• The most consistent findings according to frequency are: * Jaundice

* Splenomegaly

* Anaemia

HEREDITARY SPHEROCYTOSIS (HS)

Clinical Manifestations (cont…):• Haemolysis can be compensated for, with normal

haemoglobin in about 1/3 of the patients

• Patients may be more yellow than sick

• Cholelithiasis is a complication of HS

• HS as any other congenital haemolytic anaemia has a

STEADY STATE and EPISODIC CHANGES

HEREDITARY SPHEROCYTOSIS (HS)Laboratory Tests and Findings:* Peripheral blood film\

> 1-2% spherocytes in significant

* MCHC is increased or in the upper limit of normal range (due to decreased water content)

* Increased osmatic fragility (O.F)

Shift to the right of the entire curve or only part of it

Draw backs of this test:

- Laborious test

- Needs fresh defibrinated blood

- Not specific for HS (can be increased in AIHA)

- Insufficiently sensitive

(10-25%) of patients genetically proven to have HS have normal O.F)

* Acidified glycerol lysis time. The rate of haemolysis (The time required for 50% lysis). Normal values > 1800 seconds)

* Auto haemolysis (Screening test). 48 hours incubation under sterile conditions

HEREDITARY SPHEROCYTOSIS (HS)

Spherocytes

HEREDITARY ELLIPTOCYTOSIS (HE)

Elliptocytes

HEREDITARY STOMATOCYTOSIS (HST)

Stomatocytes

HEREDITARY SPHEROCYTOSIS

HEREDITARY SPHEROCYTOSIS (HS)Autohaemolysis Test

Lysis in a typical case (%) No addition + 27 mmol glucose

Condition

0.15 1.7 Normal

1.3 10.1 Hereditary spherocytosis

6.1 5.5 Pyruvate kinase deficiency

1.8 2.9 G6PD deficiency with CNSHA*

* In the more common forms of G6PD deficiency without chronic non spherocytic haemolytic anaemia (CNSHA) the autohaemolysis test is normal

HEREDITARY SPHEROCYTOSIS (HS)

Differential diagnosis IF SPHEROCYTOSIS is prominent:

Acquired haemolytic anaemia

DAT

FAMILY DATA

Red cell fragmentation favours

poikilocytosis microangiopathic process

Fever may favor rare infectious cause for haemolysis (Clostridium welchii)

IF SPHEROCYTOSIS is not prominent with chronic course:

PNH ---- Ham test – flowcytometry – molecular genetic

Enzymopatheis ---- O.F. usually normal or decreased

Autohaemolysis not corrected by glucose

HEREDITARY SPHEROCYTOSIS (HS)

Complications Leg ulcers Gall stones (Often asymptomatic) Aplastic crises

HEREDITARY SPHEROCYTOSIS (HS)

Management No cure The aim is to minimize the consequences of the

genetic abnormality Splenectomy

Avoid below the age of 5 years unless haemolytic anaemia is very severe (rare is HS)

Pneumococcal vaccination – (regular penicillin for at least 2 years)

Treatment of complication’s as arises

Different forms of elliptocytosis Remarks Example of

known molecular lesion

Degree of haemolysis

Genetic status

Sub type of hereditary

elliptocytosis (HE)

One parent has similar picture Structurally abnormal α–

spectrin

Absent Heterozygote Common Non-haemolytic

One parent has similar picture Glycoprotein C deficiency

Minimal Heterozygote Mild

One parent has similar picture Moderate Heterozygote Intermediate

One parent has HE: some times both

Severe Heterozygote Severe

Usuallybot parents asymptomatic. Or one has HE

Structurally abnormal α–

spectrin

Severe Homozygote Pyropoikilocytosis

Deletion revealed at DNA level (Conoboy et al., 1986)

Absence of protein 4.1

Mild Severe

Heterozygote Homozygote

Spherocytic

Common in Melanesians ? Protects against malaria

Absent or mild

Not well defined

Stomatocytic