Sickle Cell Disease

Sickle cell disease (SCD) is a group of inherited blood disorders in which red blood cells contain an abnormal form of haemoglobin called haemoglobin S. Unlike normal round and flexible red blood cells, sickle cells are rigid and crescent-shaped. They can block small blood vessels, reducing oxygen delivery to tissues and causing severe pain, anaemia, and progressive organ damage. Nigeria has the highest burden of sickle cell disease in the world, with approximately 150,000 babies born with the condition each year. Sickle cell trait — carrying one sickle gene without having the disease — affects an estimated 25–30% of Nigerians. While SCD is a lifelong condition, comprehensive care dramatically improves quality of life and life expectancy.

SCD is characterised by periods of stability punctuated by acute crises. Symptoms begin in early infancy. Chronic anaemia: • Pallor of the eyes, skin, and palms • Fatigue and weakness • Shortness of breath • Rapid heartbeat • Jaundice (yellow colouring) from red blood cell breakdown Vaso-occlusive (pain) crisis — the most common acute event: • Sudden, severe pain in the bones, joints, chest, or abdomen • Typically lasts hours to days • Often triggered by infection, dehydration, cold, stress, or fatigue Other acute events: • Acute chest syndrome: chest pain, fever, difficulty breathing: medical emergency • Stroke: sudden weakness, slurred speech, seizures • Splenic sequestration: sudden spleen enlargement with rapid anaemia: especially in young children • Aplastic crisis: sudden halt of red cell production, usually after parvovirus B19 infection • Priapism: prolonged painful erection in males Chronic features: • Delayed growth and puberty • Leg ulcers • Avascular necrosis of the hip or shoulder • Gradual organ damage (kidneys, lungs, eyes, liver)

SCD is caused by inheriting two copies of the mutated HBB gene — one from each parent — coding for haemoglobin S instead of normal haemoglobin A. Genetics: • Two parents with sickle cell trait (AS genotype) have: – 25% chance of SCD (SS) per pregnancy – 50% chance of sickle cell trait (AS) – 25% chance of normal (AA) Mechanism: • Haemoglobin S molecules clump together when oxygen levels fall, deforming red cells into a sickle shape • Sickle cells survive only 10–20 days (vs 120 days for normal cells), causing chronic anaemia • Sickle cells are rigid and sticky, blocking small blood vessels: causing pain crises and organ damage

• Genotype SS (most severely affected) • Genotype SC (one HbS, one HbC copy): milder but still significant disease • Two parents who are AS (sickle cell trait carriers) • High prevalence regions: sickle gene is most common in malaria-endemic areas of West Africa, Central Africa, the Mediterranean, and the Middle East (the sickle gene historically conferred some protection against malaria in the carrier state)

• Stroke: occurs in up to 11% of children with SCD by age 20 • Acute chest syndrome: a leading cause of hospitalisation and death • Chronic kidney disease and kidney failure • Pulmonary hypertension • Avascular necrosis of the hip • Leg ulcers • Progressive eye damage (proliferative sickle retinopathy) and vision loss • Gallstones from chronic haemolysis • Priapism leading to erectile dysfunction • Serious bacterial infections: impaired spleen function increases susceptibility • Growth retardation in children • Chronic pain and significant psychological burden

Genetic counselling and premarital screening: • Couples should know their genotype before marriage • If both partners are AS, each pregnancy carries a 1 in 4 chance of producing a child with SCD • Free genotype testing is available at most Nigerian hospitals For people living with SCD: • Take daily folic acid to support red cell production • Children under 5: daily penicillin V prophylaxis to prevent pneumococcal sepsis • Stay well hydrated: dehydration triggers sickling • Avoid cold temperatures, over-exertion, and altitude • Receive all recommended vaccinations (pneumococcal, meningococcal, Hib, influenza, hepatitis B) • Hydroxyurea (hydroxycarbamide): reduces pain crises and acute chest syndrome; discuss with your doctor • Attend regular clinic monitoring appointments