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Answer to Case of the Week 54

Answer: Trypomastigotes and intermediate trypomastigote/amastigote forms of Trypanosoma cruzi.

Thanks to everyone who wrote in for this case! This was, admittedly, a tricky case, since it is uncommon to see amastigote-type forms in peripheral blood. The reason these atypical forms were present is because this specimen was grown in culture and then innoculated in peripheral blood (artificial infection). Fortunately, the classic “C-shaped” trypomastigote forms with large kinetoplast were still abundant and allowed accurate identification. Although you wouldn’t expect to see a case like this in nature, this type of preparation may show up on proficiency test (since this material is typically grown in culture). Another important point of this case is that the forms on the thick smear resemble Plasmodium rings; thus, it is always important to examine BOTH the thick and thin smears!

Case of the Week 54

The following were seen on a Giemsa-stained thick blood film made from EDTA whole blood. Identification?

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Answer to Case of the Week 53

Answer: You should advise him that this is not an Ixodes scapularis tick, which is the agent of Lyme disease, as well as babesiosis and anaplasmosis. Instead, it is a Dermacentor tick, which can transmit Rocky Mountain spotted fever. Unlike I. scapularis, Dermacentor spp. ticks have a “chalise-shaped” anal groove and festoons (not well visible here). The most striking feature of the photographs shown are the markings on the scutum, which also are suggestive of Dermacentor, and not Ixodes spp. ticks.

Routine prophylaxis of tick-borne diseases is not generally recommended; instead, you should tell him to monitor himself for symptoms of a tick borne disease (e.g. headache, myalgia, fever, rash, influenza-like illness) and see a physician immediately should any symptoms appear.

Case of the Week 53

Welcome back to Case of the Week! It’s been a while since our last post due to the holiday, but now we’re back on schedule with a fun video for you:

The following insect was removed from the flank of a Medical Resident from Minnesota who had mistaken it for a ‘mole’ or ‘skin tag’. He notes that it had been present for at least 5 days. He is concerned that he is now at risk for an arthropod borne disease; specifically he is worried about Lyme disease. What should you tell him?

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Answer to Case of the Week 52

Question 1. Malaria due to Plasmodium malariae infection. Notice that there is no stippling present, and that the infected red blood cells are the same size or slightly smaller than the neighboring uninfected cells. Also shown here are the ‘classic’ stages of P. malariae in peripheral blood.

Question 2. From top to bottom, the forms and nicknames are:
a. Early stage trophozoite or Ring form (Nicknamed bird’s eye because the chromatin dot appears to be inside the ring like an eye)
b. Late stage trophozoite (Nickname: Band form)
c. Late stage trophozoite (Nickname: Basket form)
d. Mature Schizont (Nicknamed Rosette, or ‘daisy head’ because the merozoites line up around a central ball of granular brown-yellow pigment like petals on a flower).

Thanks to everyone for their comments!

A few smiling faces…

A couple “smiley” faces from a bone marrow we reviewed a few months ago.  I haven’t posted in a while, but promise to publish a couple interesting cases soon!