Sunday, May 15, 2016

Answer to Case 396

Answer:  Plasmodium vivax

Thanks to everyone who wrote in on this case. As nicely described by Florida Fan, Yasir and Antonio, the infected red blood cells are larger than the uninfected neighboring cells and Schuffner's dots (stippling) are present, thus indicating that this is either P. vivax or P. ovale infection. You can then narrow down the choices by noting the ameboid chromatin which is most consistent with P. vivax. Some softer features of P. vivax that are also seen in this case are the 'hugging' or 'molding' of infected cells to neighboring cells and the predominance of rounded rather than oval forms.

Florida Fan does point out that the last picture shows what appears to be fimbriation (jagged edges) which is commonly seen in P. ovale. I However, this is also a rather soft feature when only seen occasionally, and I wouldn't let a single cells with possible fimbriations steer me towards P. ovale if the other features are supportive of P. vivax. (I added this last photo in to see if it would fool anyone and was very happy to see that it didn't! You are all too smart for that).

Finally, the history of travel to India is most consistent with P. vivax infection, since this species is responsible for the majority of malaria cases there (with P. falciparum causing most of the remaining cases). In comparison, reports of P. ovale malaria in India are very rare.

No comments: