This week's case is from Dr. Steven Ruhoy and Tracie Rose. The patient is an elderly woman with a very itchy rash which is worse at night. The family practitioner noted excoriations on the plantar aspect, but did not see any definitive burrows. She performed a skin scraping which revealed the following on H&E-stained histologic section. What is your identification?
These week's case was generously donated by Dr. Linoj Samuel. The following objects were seen in the sputum from a renal transplant recipient. He had presented with pneumonia and Klebsiella sp. bacteremia.
What is your diagnosis?
Answer to the Parasite Case of the Week 793: Strongyloides stercoralis L3 (filariform) larvae
This case shows the classic features of the L3 larvae with a blunt-ended (and subtly-notched) tail.
Some of you noted the shorter larva as well, which is reminiscent of an L1 larva. However, this would be unlikely given the lifecycle of S. stercoralis.
I also considered if this could be an L4 larva, given Dr. Richard Bradbury's excellent 2024 JCM publication. However, these rarely-seen L4 larvae have a pointed or cone-shaped tail rather than a blunt, notched tail.
The number of larvae and the host's immunocompromised state are concerning for hyperinfection syndrome. When we see one of these cases in my lab, we immediately call the patient's primary care team to alert them.
Thanks again to Dr. Linoj Samuel for donating this great case!
This week's impressive case was donated by Drs. Ashley Zeoli, Nico Herrera, Luke Pryke, and Paul Blair. The patient is a young man with no significant medical history who presented with right upper quadrant abdominal pain. The pain had been present for several years, but recently worsened to the point that he sought medical care. He is originally from India.
Here was the CT from admission which shows a large, complex cyst in the liver:
Answer to the Parasite Case of the Week 792: Echinococcal cyst, most likely due to E. granulosus.
This case shows several classic findings:
This week's case is from Drs. Matt Pettengill and Sean Moss. Approximately 10 of the following object were recovered from the hair of patient. She had applied calendula to her scalp earlier in the day. What is your identification?
Answer to the Parasite Case of the Week 791: Not a parasite; most closely resembles calendula seeds.
This was a fun case to try to figure out! Almost everyone correctly recognized that this object was not a parasite, and the history of calendula application quickly pointed many of you toward the true source. I consulted our botanist colleague, Dr. Mary Parker, who agreed that this object closely matches a calendula seed.
Here’s a comparison image from the USDA website (top) and our current case (bottom):
Calendula, a genus in the daisy family (Asteraceae), is commonly known as marigold. Calendula-based products, especially calendula oil, are often promoted for hair growth and scalp soothing, though I wasn’t able to find supporting evidence for these claims in PubMed.
As you can see from the photo, Calendula seeds are small, curved, and ridged, making them look surprisingly similar to certain larval insect forms or even trematodes. A great reminder that context and collaboration are key in solving these “parasite mimicker” mysteries!
Thanks again to Drs. Moss and Pettengill for sharing this great case.
