One Haemolytic Anaemia May Hide Another: Paroxysmal Nocturnal Haemoglobinuria Masquerading As Plasmodium Falciparum Infection.

Background: Paroxysmal nocturnal haemoglobinuria (PNH) is a rare, genetic and acquired haematologic disease that causes complement-mediated intravascular haemolytic anaemia, thrombosis and bone marrow failure.

Case description: A 27-year-old migrant patient attended the emergency department in a context of fever and chills over the previous few days as well as chronic fatigue, dyspnoea and chest pain. His medical history included chronic anaemia and erectile dysfunction. Initial biology showed a haemoglobin of 6.3 g/dl, platelets of 25,000/μl, total leucocytes of 3,500/μl with 1,500 neutrophils. B12 vitamin, folic acid, ferritin and thyroid stimulating hormone were normal. Lactate dehydrogenase levels were high and haptoglobin was non-measurable. C-reactive protein was 46.1 mg/l. A thick blood smear revealed Plasmodium falciparum infection with 0.1% parasitaemia. The patient was treated with an oral combination of artemether and lumefantrine. Three weeks later, the patient consulted the infectious disease department given the lack of clinical improvement. The cytopenias worsened, and lactate dehydrogenase (LDH) and reticulocytes increased. Tests for schistocytes, a thick blood smear for malaria and a direct Coombs test were negative; a myelogram was reassuring. An abdominal, pelvic and thoracic CT scan showed a mild hepatomegaly with no focal lesion and no splenomegaly or adenomegaly. A 12-colour flow cytometry unveiled a PNH clone on 90.9545% of neutrophils and 80.7371% of monocytes.

Discussion: PNH patients can be vulnerable to parasites infection (such as P. falciparum) as it may trigger breakthrough haemolysis through uncontrolled resurgence of activity of the complement system. In our patient, P. falciparum infection was a confounding factor, as it commonly causes haemolytic anaemia and thrombocytopenia, and patients living in malaria-endemic regions can carry low parasitaemia while being slightly symptomatic or asymptomatic.

Learning points: Plasmodium falciparum infection can cause breakthrough haemolysis in patients with paroxysmal nocturnal haemoglobinuria.Low P. falciparum parasitemia in patients living in malaria-endemic regions is not always significant as these patients often carry acquired immunity.Patients from malaria-endemic regions presenting with severe sickness and low P. falciparum parasitemia must be assessed for other diseases, as it cannot explain heavy illness.Patients presenting with haemolytic anaemia, no schistocytes, a negative direct Coombs test and other unexplained cytopenia such as thrombocytopenia/neutropenia and other unexplained clinical manifestations such as dyspnoea, chest pain or erectile dysfunction should be assessed for paroxysmal nocturnal haemoglobinuria.