Monday, April 22, 2024

Case of the Week 746

Welcome back to our microfilariae block from Idzi Potters and the Institute of Tropical Medicine, Antwerp! We are down to the last TWO specimens. This week's case is from a skin specimen - both skin samples AND a subcutaneous nodule (removed from the upper arm). The patient is a young man from Brazil.

Here is the nodule:

And here are the skin scarification specimens (read more about scarification vs. skin snips HERE):

Carazzi stain:

Giemsa stain:

The microfilariae are approximately 300 micrometers in length. What is your diagnosis?


Anonymous said...

The Carrazi stain did not show a sheath. The source is skin narrows the etiology down to only two microfilarias: Mansonella streptocerca and Onchocerca volvulus. Since Mansonella streptocerca is only around 200 micrometers long and possesses a curved tail, we can identify the microfilaria as being Onchocerca volvulus with confidence.
Florida Fan

Anonymous said...

Actually, there’s one more point of distinction: the column of nuclei of Onchocerca volvulus stops short of the tail, whereas the column of nuclei of Mansonella streptocerca continues to the end of the tail.
Florida Fan

Anonymous said...

great valuable differential diagnosis