Identification?

Congratulations to Anonymous (x 3!), Kenneth, Chris, Victor, and Santoshpath who all got this correct! The keys to the diagnosis is the clinical history (location in nasal mucosa), exposure history (India), and histopathologic features of a polypoid mass containing mature sporangia (large, thick-walled spherical structures) and smaller internal sporangiospores (daughter cells). The sporangia stain with the fungal stains Gomori methenamine silver (GMS) and periodic acid-Schiff (PAS), and may mimic the appearance of similar appearing fungi such as Coccidiodes immitis (as one viewer suggested) and Chrysosporium spp. (the agent of adiaspiromycosis). Myospherulosis, a non-infectious entity, is also in the differential diagnosis. The difference between these entities is in the size of the spherule/sporangia and the internal structures.

This organism was previously considered to be a fungus, but it is now considered to be an aquatic protistan parasite (classified under Mesomycetozoea, which includes parasites of fish and amphibians). Rhinosporidiosis is endemic in India, Sri Lanka, South America, and Africa.

Although the disease most commonly involves the mucosa of the nose, mouth, and conjunctiva, involvement of the skin, ear, genitals, and rectum has also been described. Disseminated infection has been described in 3 individuals.

Thank you all for viewing and writing in!

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!

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.

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?

Click here to view the embedded video.

Here are some accompanying images to aid in identification.

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!

Question 1 – What organism (genus and species) is shown?
Question 2 – What is the nick-name of each stage?

I included this case since the object in some of the photos resembles a helminth egg (Toxocara canis or Capillaria spp. comes to mind). The key to recognizing that this is not an egg is in the last photograph which clearly shows the pores in the thick outer layer and triangular shape of the inner structures. There are no human parasites that have eggs in this configuration.