Recrudescing Plasmodium malariae infection despite appropriate treatment in an immigrant toddler

Compared with other plasmodium species which cause human malaria, Plasmodium malariae is considered to be relatively infrequent and milder, although recent reports indicate that its prevalence and impact have been under-estimated. A 23-month-old boy, born and previously living in a refugee camp in Liberia who presented with P. malariae 6 weeks after arrival in the USA, is reported. Despite ostensibly effective anti-malarial treatment with artemether/lumefantrine and two courses of hydrochloroquine, he experienced recurrent parasitaemia, refractory anaemia and splenomegaly over a 6-month period; the symptoms resolved after he received atovaquone/proguanil. It is hypothesised that the recrudescing clinical malaria in this case was related to the long pre-erythrocytic phase unique to P. malariae, and potentially also to a proportion of the parasites being drug-resistant.