Monday, May 17, 2010

Case of the Week 117

The following images were taken from a Giemsa-stained peripheral blood smear. The different stages of the organism shown represent a single species, and each stage is characteristic for this species. The stages are so characteristic, in fact, that each has an 'unofficial' name (e.g. nick-name) or description.

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


Sunday, May 16, 2010

Answer to Case 117

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!

Sunday, May 9, 2010

Case of the Week 116

The following were seen in a concentrated wet preparation of stool. No history is available. Identification? (CLICK ON IMAGES TO ENLARGE)

(40x objective)

(100x objective)

(100x objective)

(100x objective)

(100x objective)

Saturday, May 8, 2010

Answer to Case 116

Answer: Not a parasite. Most closely resembles pollen.

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.

Monday, May 3, 2010

Case of the Week 115

The following were removed from a patient's ear where they appeared to be feeding on necrotic tissue associated with a large tumor. Diagnosis?

Sunday, May 2, 2010

Answer to Case 115

Answer: Fly larvae; myiasis.

Although the images don't provide enough detail to make a definitive identification to the genus and species level, it is clear that these are insect larvae. The fact that they were found associated with necrotic human tissue suggests that they are facultative human parasites, and thus the term myiasis (dipterous fly larvae feeding on the host's necrotic or living tissue) applies. Of interest, "myia" is Greek for fly.

Thanks for all of the comments!