It's time for our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. As always, Idzi has a great case for us - courtesy of Anna Rosanas and Pieter Guetens from ITM's Malariology Department: a patient with extensive recent travel - leaving Belgium to trek across rural areas of Peru, Niger, Mali, and finally the Philippines. He didn't take any malaria prophylaxis while traveling and now presents with fever and general malaise after being home for 3 weeks. The following are thick and thin Giemsa-stained blood films from this patient (pH 8.0). The percent parasitemia was calculated at 1%. Identification?
Sunday, June 6, 2021
Answer to the Parasite Case of the Week 642: Plasmodium sp. infection with relatively high (1%) parasitemia; differential diagnosis includes mixed P. falciparum/P. malariae infection and P. knowlesi infection. Recommend nucleic acid amplification testing for definitive identification.
PCR testing confirmed that this was P. knowlesi infection!
This interesting case highlights the difficulty in diagnosing P. knowlesi infection, given that many of its key morphologic features in humans overlap with those of P. falciparum and P. malariae. Like P. falciparum, high parasitemias may be observed, and thin delicate rings - occasionally with double chromatin dots ("headphone" forms) and applique forms - may be seen. Conversely, all stages of P. knowlesi are commonly seen in peripheral blood, unlike most cases of P. falciparum, so that late stage trophozoites and schizonts are also seen. Many of these later stage forms resemble those of P. malariae, such as "band form" late stage trophozoites. Of note, P. malariae does not reach high levels of parasitemia (1% would be unexpectedly high).
Given this complexity, PCR confirmation is important for understanding the nature of infection and guiding therapy.
Tuesday, June 1, 2021
This week's case was generously donated by Dr. Alexander Fenwick and includes some beautiful images.
The following objects were seen in a sputum specimen from a patient living in Eastern Kentucky. This patient was receiving corticosteroid therapy for poorly-controlled COPD. Identification?
Gram stain (10x and 100x magnification)