G6PD deficiency and enzymopathies: SAQ

This child has an acute haemolytic crisis of glucose-6-phosphate dehydrogenase deficiency triggered by fava beans. The Mediterranean ancestry, the fava bean exposure, the sudden pallor with dark urine, the severe anaemia with a high reticulocyte count, the negative direct antiglobulin test, and the blood film with bite cells, blister cells and Heinz bodies together make the diagnosis. He needs immediate supportive care, transfusion for his severe anaemia, and definitive trigger-avoidance counselling and family screening. ^[1][9]

Question 1 (10 marks)

Explain the pathophysiology of this child's haemolysis and outline your immediate management. ^[1][2]

The mechanism is oxidative haemolysis. G6PD is the first enzyme of the pentose phosphate pathway and generates NADPH, which keeps glutathione in its reduced form; reduced glutathione neutralises the oxidants generated inside the red cell. In G6PD deficiency, the oxidants in fava beans consume the limited NADPH and reduced glutathione faster than they are regenerated, so the defence collapses. The oxidants denature haemoglobin into Heinz bodies, which the spleen pits out to form the bite cells and blister cells on the film, and the damaged membrane lyses, causing the intravascular haemolysis that colours the urine dark. ^[1]

Immediate management begins with removing the trigger, which here is the fava beans, and assessing airway, breathing and circulation. He is tachycardic and pale with a haemoglobin of 54 g per litre, which is well below the transfusion threshold, so he needs crossmatched leucodepleted packed red cells at 10 to 20 mL per kilogram. Ensure hydration to protect the kidney from haemoglobinuria and give folic acid to support marrow recovery. Monitor the haemoglobin, urine output and renal function, and escalate to intensive care if he develops acute kidney injury or haemodynamic instability. ^[9]