Answer to Case 592

Answer toParasite Case of the Week 592:Plasmodium malariae;likely recrudescent infection, given that he has been without symptoms for> 2 months since his last travel to sub-Saharan Africa. WhileP. knowlesiis also in the differential based on the morphologic overlap betweenP. knowlesiandP. vivax,the long period of time since his travel to SE Asia would be atypical forP. knowlesiinfection.Some of the classicP. malariaefeatures seen in this case are the small size of the infected red blood cells, schizonts with only 6-12 merozoites, band forms, and a basket form:A tip for those studying for boards - be sure you know the difference between recrudescence and relapse.Recrudescence - seen primarily withP. malariaeinfection, but can also be seen with other Plasmodium species that lack hypnozoites.Recrudescence refers to recurrence of infection. With P. malariae,recrudescence is thought to be due to the indolent growth of this parasite, enabling survival for many years, even with chloroquine treatment. Chloroquine is the drug of choice forP. malariaeinfections, and it is preferentially concentrated in the food vacuoles of metabolically active trophozoites. Here it binds to hematin and prevents its polymerization, resulting in oxidative stress to the parasite and eventual lysis. Given the low growth and metabolism of P. malariaeasexual stages, some trophozoites can escape the action of chloroquine and later cause disease recrudescence. Recrudescence is different ...
Source: Creepy Dreadful Wonderful Parasites - Category: Parasitology Source Type: blogs