Abstract
BackgroundFalciparum Malaria, an infectious disease caused by the apicomplexan parasite Plasmodium falciparum, is among the leading causes of death and morbidity attributable to infectious diseases worldwide. In Gabon, Central Africa, one out of four inpatients have severe malarial anemia (SMA), a life-threatening complication if left untreated. Emerging drug resistant parasites might aggravate the situation. This case control study investigates biomarkers of enhanced hemolysis in hospitalized children with either SMA or mild malaria (MM).Methods and FindingsNinety-one children were included, thereof 39 SMA patients. Strict inclusion criteria were chosen to exclude other causes of anemia. At diagnosis, erythrophagocytosis (a direct marker for extravascular hemolysis, EVH) was enhanced in SMA compared to MM patients (5.0 arbitrary units (AU) (interquartile range (IR): 2.2–9.6) vs. 2.1 AU (IR: 1.3–3.9), p<0.01). Furthermore, indirect markers for EVH, (i.e. serum neopterin levels, spleen size enlargement and monocyte pigment) were significantly increased in SMA patients. Markers for erythrocyte ageing, such as CD35 (complement receptor 1), CD55 (decay acceleration factor) and phosphatidylserine exposure (annexin-V-binding) were investigated by flow cytometry. In SMA patients, levels of CD35 and CD55 on the red blood cell surface were decreased and erythrocyte removal markers were increased when compared to MM or reconvalescent patients. Additionally, intravascular hemolysis (IVH) was quantified using several indirect markers (LDH, α-HBDH, haptoglobin and hemopexin), which all showed elevated IVH in SMA. The presence of both IVH and EVH predicted the need for blood transfusion during antimalarial treatment (odds ratio 61.5, 95% confidence interval (CI): 8.9–427). Interestingly, this subpopulation is characterized by a significantly lowered reticulocyte production index (RPI, p<0.05).ConclusionsOur results show the multifactorial pathophysiology of SMA, whereby EVH and IVH play a particularly important role. We propose a model where removal of infected and non-infected erythrocytes of all ages (including reticulocytes) by EVH and IVH is a main mechanism of SMA. Further studies are underway to investigate the mechanism and extent of reticulocyte removal to identify possible interventions to reduce the risk of SMA development.
Highlights
Malaria due to Plasmodium falciparum is the most important parasitic disease worldwide; approximately 270 million people get infected and 1 to 3 million deaths occur every year, most of them in sub-Saharan Africa [1]
Our results show the multifactorial pathophysiology of severe malarial anemia (SMA), whereby EVH and intravascular hemolysis (IVH) play a important role
We propose a model where removal of infected and non-infected erythrocytes of all ages by EVH and IVH is a main mechanism of SMA
Summary
Malaria due to Plasmodium falciparum is the most important parasitic disease worldwide; approximately 270 million people get infected and 1 to 3 million deaths occur every year, most of them in sub-Saharan Africa [1]. Complications leading to death include severe malarial anemia (SMA), cerebral malaria, hypoglycemia, lactic acidosis and convulsions. An epidemiological survey undertaken at the same time period than the presented study showed that 25% of all 1 month to 10 years old hospitalized malaria patients had severe anemia, 95% of whom were younger than 5 years old [5]. Emerging drug resistant parasites might aggravate the situation. This case control study investigates biomarkers of enhanced hemolysis in hospitalized children with either SMA or mild malaria (MM)
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