This week's case features small (~2 micrometer long), oval-shaped objects seen in a corneal scraping. Thanks to Heather for taking these beautiful images. The stain is strong trichrome (chromotrope 2R method).
What is the most likely diagnosis?
Answer to the Parasite Case of the Week 655: Microsporidia spores. Nucleic acid amplification/sequencing and/or electron microscopy is required for genus and species level identification.
Microsporidia that are commonly implicated in corneal infection include Vittaforma corneae and Encephalitozoon hellem.
As noted by Dr. Harsha Sheorey, the Ryan’s modified Trichrome stain was created by his friend and colleague, Dr Norbert Ryan. This stain has now become a standard staining technique for these organisms, and what was used in this case. The microsporidia spores stain bright red against a blue background.
This week's case is of a middle-aged man with a painful lesion on the dorsum of his foot. He recently returned from Brazil, during which he swam in the ocean, walked barefoot on the beach, and ate local foods. An excisional biopsy was performed and submitted to the clinical microbiology lab to rule out a possible parasite. The specimen received was an excised ellipse of skin on which there was a central defect measuring ~ 5 mm in diameter:
Answer to the Parasite Case of the Week 654: Tunga sp. flea
I encourage you to check out the posts in the Comments section by Kosta and Florida Fan who give us an excellent description of the taxonomy, morphology, epidemiology, and clinical presentation of this parasitic flea.
Here are some of the diagnostic features from this case:
Tunga sp. eggs measuring ~0.6 mm long:
This week's case was generously donated by Drs. Alex Fenwick and Julie Ribes at the University of Kentucky. The following structure was retrieved from bronchial washings of a patient with end-stage lung disease due to cystic fibrosis.
Answer to the Parasite Case of the Week 653: Not a human parasite; most likely a mucus cast.
As noted by Florida Fan, "The object did not have any internal organization nor visible external anatomy. It displays a ribbon like morphology being flat and slender especially at the bend."
Sam had a similar thought and suggested that since the "patient had cystic fibrosis it may be some kind of mucous plug."
To test these hypotheses, we can gently manipulate the object. Mucus usually separates easily whereas a true nematode has a firm, rubbery cuticle and is harder to tear. As CA noted, although not a first choice, we could also put a section through for histopathology. Histopathologic examination can be extremely helpful in several instances, such as when looking for the characteristic lateral cords of the anisakids (see Case of the Week 177) or the uterine branches of Taenia spp. proglottids (See Case of the Week 361).
Thanks again to Drs. Ribes and Fenwick for donating this interesting case!
Happy Labor Day weekend to my American readers! It's the first Monday of the month, and time for our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following structures were seen in Ziehl-Neelsen stained sputum specimen for acid fast bacilli, thus prompting additional examination of direct wet mounts. The patient had recently from Sicily.
Ziehl-Neelsen stained sputum specimen:
Direct wet mount:
Answer to the Parasite Case of the Week 652: Strongyloides stercoralis L3 (filariform) larvae.
As nicely described by Luis, "We can see in photo 2 an esophagus almost as long as the intestine, the tail is sharp and has notches (photo 3)."
The notches are classic and can be seen in both the the Ziehl-Neelsen (ZN) stained preparation and wet prep (inset), (arrows).
The ZN stain had been performed to screen for acid fast bacilli (AFB). AFBs would stain bright red with the carbol fuchsin dye, whereas the larva is only stained here with the methylene blue counter stain.
This case goes well with last week's, in which we saw L1 (rhabditiform) larvae of S. stercoralis.
Thanks again to Idzi for donating this great case!