Blackwater fever — DTM&H MCQ

Correct answer: D — Blackwater fever complicating falciparum malaria

The correct answer is D, blackwater fever complicating falciparum malaria. This patient has a confirmed falciparum blood film, severe haemolytic anaemia (Hb 72 g/L), jaundice, dark cola-coloured urine (haemoglobinuria) and acute kidney injury (creatinine 210 umol/L), which together represent massive intravascular haemolysis from severe P. falciparum infection. UK malaria treatment guidelines list haemoglobinuria (without G6PD deficiency) as a recognised feature and poor prognostic marker of severe/complicated falciparum malaria, reflecting parasite-driven red cell destruction and free haemoglobin causing tubular injury. The negative direct antiglobulin test excludes an antibody-mediated (autoimmune) process, confirming the haemolysis is intravascular and parasite-related rather than immune-mediated. This constellation in a returning traveller from a highly endemic area with a positive falciparum film is the classic presentation of blackwater fever. Why the other options are wrong: A. G6PD deficiency alone: this would not explain the positive falciparum film; G6PD deficiency causes oxidative haemolysis typically triggered by drugs or fava beans, and while it can compound antimalarial-induced haemolysis, it does not account for the parasitaemia itself and there is no mention of an oxidant drug trigger. E. Acute viral hepatitis A: causes jaundice but not haemoglobinuria, severe anaemia to this degree, or a positive malaria film; it is a hepatocellular process, not a haemolytic one. C. Autoimmune haemolytic anaemia: excluded directly by the negative direct antiglobulin test, which would be positive in antibody-mediated haemolysis. B. Leptospirosis with pulmonary haemorrhage: can cause jaundice and renal impairment (Weil's disease) but there is no respiratory bleeding described, and the positive falciparum film makes malaria-related haemolysis the unifying diagnosis. Key point: haemoglobinuria plus a negative direct antiglobulin test in a patient with confirmed falciparum parasitaemia points to blackwater fever from massive intravascular haemolysis, not immune haemolysis or an unrelated hepatic/leptospiral cause.

Reference: Lalloo DG, Shingadia D, Bell DJ, Beeching NJ, Whitty CJM, Chiodini PL; PHE Advisory Committee on Malaria Prevention in UK Travellers. UK malaria treatment guidelines 2016. J Infect. 2016;72(6):635-649 (lists haemoglobinuria without G6PD deficiency as a feature/prognostic marker of severe falciparum malaria). https://pmc.ncbi.nlm.nih.gov/articles/PMC7132403/