[Sickle cell anemia, an example of a constitutional disease of hemoglobin]

Sickle cell anemia is a congenital haemolitic anemia. The replacement of the hydrophilic glutamine residue at the 6 position of the beta chain by the hydrophobic valine leads to severe conformation change in the molecule resulting in sickling. The consequences are haemolysis, vascular stasis and thrombotic crisis. Infection triggers thrombosis and vice-versa. Clinical manifestation is anemia punctuated by intermittent crisis producing infarction. Pneumococcal and salmonella infections are frequent mainly in the lungs and bones. Prognosis is poor, half of the patients dying before 20 years. Prompt treatment of infection is important. Treatment includes good nutrition and administration of folic acid. Transfusions are often usefull to avoid hazards of anesthesia or surgery. Ante natal diagnosis based on smaller sample of foetal blood or amniotic liquid is now possible.