Case of the Week 558

This week's case presents a bit of a conundrum. The patient is a 50 year old woman with recent travel to Kenya. She presents with acute onset of fever and chills and was tested by a rapid malaria antigen test (P. falciparum and Pan-malaria antigens) and was negative. A follow-up Giemsa-stained thin blood smear from the same blood collection shows the following (image below). What is the identification based on the blood smear? How might this correlate with the rapid antigen test?

Read Dr. Pritt's blog, Parasite Wonders, and submit your answers, comments, and questions. Also, visit her website ParasiteWonders.com, which hosts an archive of classic images from cases Dr. Pritt has posted going back to 2007 (in an easy-to-search "A through Z" format) and also offers a flashcard feature.

Answer to Case 558:

Plasmodium falciparum malaria, >10% parasitemia. NEGATIVE rapid antigen

Bobbi Pritt, M.D.

Bobbi Pritt, M.D.

Bobbi Pritt, M.D., is Director of the Clinical Parasitology Laboratory in Mayo Clinic's Department of Laboratory Medicine and Pathology. Her research interests are in clinical parasitology, vector-borne diseases, trainee education, and appropriate test utilization.