A 5-year-old child with sickle cell disease presents with severe pallor, tachycardia, and lethargy. Blood tests show: Hb: 4 g/dL (very low) Reticulocyte count: Low What is the most likely cause? A) Splenic sequestration crisis B) Aplastic crisis C) Haemolytic crisis D) Iron deficiency anaemia E) Thalassaemia Correct Answer: B) Aplastic crisis Explanation: Aplastic crisis in sickle cell disease is caused by parvovirus B19 infection, leading to: Severe anaemia (low Hb) Low reticulocyte count (bone marrow suppression) A) Splenic sequestration crisis → Incorrect. Causes enlarged spleen + sudden drop in Hb, but reticulocyte count is high. C) Haemolytic crisis → Incorrect. Causes low Hb, but high reticulocytes (increased RBC destruction). D) Iron deficiency anaemia → Incorrect. Unlikely in a child with sickle cell disease. E) Thalassaemia → Incorrect. Chronic anaemia, not sudden crisis. Key Tips for PLAB 1: ✅ Severe anaemia + low reticulocytes = Aplastic crisis (parvovirus B19). ✅ Treatment = Blood transfusion, supportive care.
