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Acute haemolysis in childhood falciparum malaria
1Unit of Infectious Diseases, Karolinska Institutet, Karolinska Hospital, 171 76 Stockholm, Sweden. hakekv@ki.se
Insights
Acute Plasmodium falciparum malaria causes significant red blood cell destruction, primarily through extravascular clearance. This process, marked by haemoglobin loss and increased opsonins, is crucial in malarial anaemia.
Area of Science:
- Malariology
- Haematology
- Immunology
Background:
- High-level Plasmodium falciparum parasitaemia is linked to acute haemolysis in children.
- Understanding the mechanisms of red blood cell destruction in malaria is critical for managing malarial anaemia.
Purpose of the Study:
- To investigate the mechanisms of erythrocyte clearance during acute Plasmodium falciparum malaria in children.
- To correlate haemolysis with parasitaemia levels and identify markers of severe haemolysis.
Main Methods:
- Studied 20 children with high-level Plasmodium falciparum parasitaemia in coastal Tanzania.
- Conducted balance studies measuring haemoglobin (Hb) loss, plasma Hb, and urinary Hb over 72 hours.
- Assessed erythrocyte-bound opsonins (complement C3c fragments and autologous IgG).
Main Results:
- Haemoglobin concentration decreased significantly, linearly related to maximum parasitaemia.
- Extravascular clearance was the predominant erythrocyte clearance mechanism, with minor intravascular haemolysis.
- Increased erythrocyte-bound opsonins correlated with haemolysis severity, suggesting a role in erythrophagocytosis.
Conclusions:
- Predominantly extravascular erythrocyte clearance is a key mechanism in acute malarial anaemia.
- Haemoglobinuria serves as a marker for severe haemolysis in malaria.
- Similar mechanisms may underlie erythrocyte clearance in malaria, normal senescence, and other acute haemolytic conditions.
Abstract:
Acute haemolysis associated with clinical episodes of high-level Plasmodium falciparum parasitaemia was studied in 20 children from an holoendemic area (coastal Tanzania). The change in blood haemoglobin (Hb) concentration ranged from -46 to g/L during the 72-h observation period and was linearly related to maximum parasitaemia. Balance studies between loss of blood Hb, increase in plasma Hb and appearance of Hb in the urine indicated that extravascular clearance of red cells was the predominant mode of erythrocyte clearance. Most subjects, however, showed minor signs of intravascular haemolysis. The plasma Hb was << 1% of blood Hb and haemoglobinuria was detected in 14/20 children but the excretion of Hb in urine was < 0.5% of total Hb loss. Haemoglobinuria was, however, a marker of severe haemolysis, since the maximum blood Hb loss in children without haemoglobinuria was 10 g/L. Erythrocyte-bound opsonins known to induce erythrophagocytosis, i.e., complement C3c fragments and autologous IgG, were increased in all patients. In the patients with major haemolysis, the changes correlated to the haemolysis over time. Hence, a similar mechanism for predominantly extravascular erythrocyte clearance may be operative in acute malarial anaemia, normal erythrocyte senescence and other forms of acute haemolysis.