Sickle cell disease

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Sickle cell anemia is a recessive hereditary disease due to the presence of an abnormal hemoglobin called hemoglobin S.

This complex and multi-factorial disease is very frequent in tropical areas (central Africa, Arabia, India...) but is also encountered in Western countries. One of person in Brussels on 100 is healthy carrier for the disease and more than one child on 2000 born in the capital of Europe is sick.

The genetic defect is A>T mutation in the gene coding for b-globin (codon 6). The result is a substitution of the normal amino acid (valine) by another one (glutamine).  Under low oxygen pressure conditions, the abnormal hemoglobin polymerizes, altering the red cell shape ("like a sickle") which can then block the microcirculation.

The disease is characterized by painful crises with  severe hemolysis and vaso-occlusion.

There are several forms of sickle cell diseases. The most frequent is hemoglobin S homozygosity also called Hb SS disease. States of double-heterozygosity lead to a more or less severe sickle cell disease: SC, SD-Punjab, SO-Arab, Sb-thalassemia...

Prevention and treatment are available and must be used from birth.

Phenotype Genotype Clinical presentation Biology
Healthy carrier AS Normal Normal blood examination.
Electrophoresis: presence of HbS and HbA. 
Sick patient SS, SD, SC, SO, Sb-thalassemia Hemolytic anemia appearing at 6 months of life.
Vaso-occlusive crises.
Infections.
Anemia, hemolysis, reticulocytosis.
Electrophoresis: presence of HbS and absence of HbA.

 

Last Update: 15-03-2002 - Webmaster