Sickle cell disease
- Sickle-cell disease (SCD) is an autosomal recessive condition and occurs when an individual inherits two abnormal copies of the haemoglobin gene (one from each parent). Sickle cell trait occurs with a single abnormal copy of the haemoglobin gene; the individual is known as a carrier and is usually asymptomatic. Diagnosis is made by blood test and in some countries with high prevalence, all babies are tested at birth. Diagnosis is also possible during pregnancy.
- SCD is more common in sub-Saharan Africa, India, the Arabian peninsula, and among people of African origin living in other parts of the world. There is a protective effect against malaria of sickle-cell trait.
- The problems of SCD occur due to 'sickling' of red blood cells under certain circumstances (e.g., dehydration, fever, altitude) and typically begin around 5 to 6 months of age.
- Features include attacks of severe pain ("sickle-cell crisis"), haemolytic anaemia, swelling in the hands and feet (with dactylitis), bacterial infections (osteomyelitis and septic arthritis) and vaso-occlusive features including stroke. Bone and joint damage can result following infection and there is risk of osteonecrosis.
- There is increased risk of serious bacterial infection (e.g., strep pneumoniae and haemophilus influenzae) due to loss of spleen function.
- SCD is a serious disease with high morbidity and mortality: stroke disease, renal failure, pulmonary hypertension, retinal disease-causing blindness, gallstones (pigment stones) complications of sepsis.
- Management of SCD includes infection prevention with vaccination (pneumococcal vaccine) and during attacks there needs to be prompt access to antibiotics, high fluid intake, folic acid supplementation and pain medication. Blood transfusions may be needed. Bone marrow transplantation (allogeneic) offers long term cure.