Blackwater fever — DTM&H MCQ

Correct answer: C — Blackwater fever

The correct answer is C, blackwater fever. This syndrome features massive intravascular haemolysis and haemoglobinuria precipitated by falciparum malaria, classically with recurrent quinine exposure, producing fever, jaundice, loin/back pain and dark (cola coloured) urine. The key diagnostic clue is dipstick positive for blood with few or no red cells on microscopy, which indicates free haemoglobin (haemoglobinuria) rather than intact erythrocytes, since haemoglobin and myoglobin both give a positive blood reaction on dipstick chemistry without corresponding red cells on microscopy. This combination of severe P falciparum infection, amino alcohol antimalarial exposure (quinine, mefloquine, halofantrine) and intravascular haemolysis is the classic description of blackwater fever, often accompanied by acute kidney injury. Why the other options are wrong: B. Haemolytic uraemic syndrome: typically follows Shiga toxin producing E coli or is complement mediated, presenting with microangiopathic haemolytic anaemia, thrombocytopenia and schistocytes, not linked to malaria or quinine exposure. D. Acute schistosomiasis: causes Katayama fever with eosinophilia, urticaria and hepatosplenomegaly, and chronic urinary schistosomiasis causes terminal haematuria with visible red cells and ova on microscopy, not haemoglobinuria. A. Leptospiral uveitis: uveitis is a late immune mediated complication of leptospirosis, an ocular finding unrelated to haemoglobinuria or malaria treatment. E. Dengue haemorrhage: causes thrombocytopenia, plasma leakage and bleeding manifestations, but does not produce isolated haemoglobinuria in the context of quinine treated falciparum malaria. Key point: Dipstick blood positive but microscopy showing few red cells signals haemoglobinuria (or myoglobinuria), the hallmark of blackwater fever in a patient with falciparum malaria and quinine exposure.

Reference: PMC (Malaria Journal), Blackwater fever in an uncomplicated Plasmodium falciparum patient treated with dihydroartemisinin-piperaquine, 2014, https://pmc.ncbi.nlm.nih.gov/articles/PMC3984693/