Malaria, a major cause of child mortality worldwide, is caused by mosquito-borne hematoprotozoan parasites of the genus Plasmodium. Of the 4 species that infect humans, P. falciparum causes the most severe forms of malaria and is the major cause of death and disease. Although less fatal, P. malariae, P. ovale, and, in particular, P. vivax infections are major causes of morbidity. The parasite cycle involves a first stage in liver cells and a subsequent stage at erythrocytes, when malaria symptoms occur. A wide spectrum of phenotypes are observed, from asymptomatic infection to mild disease, including fever and mild anemia, to severe disease, including cerebral malaria, profound anemia, and respiratory distress. Genetic factors influence the response to infection, as well as disease progression and severity. Malaria is the strongest known selective pressure in the recent history of the human genome, and it is the evolutionary driving force behind sickle-cell disease (603903), thalassemia (see 141800), glucose-6-phosphatase deficiency (300908), and other erythrocyte defects that together constitute the most common mendelian diseases of humans (Kwiatkowski, 2005; Campino et al., 2006). [from
OMIM]