Haematology >
Sickle Cell Anaemia
“Autosomal recessive disorder in which production of abnormal haemoglobin results in vaso-occlusive crises”
- HbSS- homozygotes, have sickle cell disease
- HbAS- heterozygotes, have sickle cell trait
Risk Factors
- Most commonly in people of African origin (1:700 people of African descent)
- Family history (parents with sickle cell trait
Aetiology
- Amino acid substitution in the gene coding for the β chain (Glu → Val at position 6) leading to the production of HbS instead of HbA
Pathophysiology
- HbS polymerizes when deoxygenated → RBCs to deform → produces sickle cells which are fragile and haemolyse, also block small vessels
Clinical Presentation
- Symptoms:
- Lethargy and general weakness
- Growth restriction
- Episodes of pain
- Swelling of hands and feet
- Frequent infections
- Vision problems
- Signs:
- Jaundice
- Pallor
- Delayed puberty
Sickle Cell Crisis
- Vaso-occlusive crises
- Most common crisis
- Precipitated by cold, infection, dehydration, exertion, ischaemia
- Occlusion of small vessels
- Swollen painful joints, tachypnoea, acute abdominal distension and pain, loin pain, retinal occlusion
- Large vessels à stroke, acute sickle chest syndrome, placental infarction
- Acute chest syndrome- vaso-occlusive in the lungs, infections in children, infarcts in adults
- Aplastic crisis
- Temporary cessation of erythropoiesis causing severe anaemia
- Usually caused by infection with parvovirus B19
- Drop-in Hb
- Spontaneous recovery but may require a transfusion
- Sequestration crisis
- Sudden enlargement of the spleen
- The pooling of blood in spleen ± liver with severe anaemia
- Urgent transfusion needed
Investigations
- FBC
- Blood film
- Sickle solubility test
- Hb electrophoresis
- Other tests:
- Renal function tests
- LFTs
- Lung function tests
Management
- Neonatal screening for sickle cell disease
- Conservative:
- Parental and patient education
- Avoid triggers of crises- cold, dehydration, exhaustion
- Avoid alcohol and smoking
- Medical:
- Hydroxycarbamide (hydroxyurea)
- Folic acid supplementation
- Zinc supplementation if growth is restricted
- Vit D supplementation especially in non-white children in the UK
- Oral penicillin prophylaxis started at diagnosis
- Routine childhood vaccinations
- Malaria chemoprophylaxis (malaria significant cause of morbidity and mortality in patients)
- Blood transfusion therapy in severe anaemia
- Surgical:
- Bone marrow transplantation only in severe disease and a matched sibling donor
- Prevention:
- Genetic counselling
- Prenatal tests
Complications
- Splenic infarction before 2 years old → increased susceptibility to infection
- Poor growth
- Chronic renal failure
- Gallstones due to chronic haemolytic anaemia
- Eye- retinopathy, retinal infarcts, retinal haemorrhage, retinal detachment
- Stroke
- Chronic pain
- Nocturnal enuresis
- Iron overload
- Leg ulcers Lung damage → hypoxia → fibrosis → pulmonary hypertension