Case of the Week 734

Welcome to the first blog post of 2024! I had been particularly busy last year as I was serving as the Interim Chair of the Department of Laboratory Medicine and Pathology at Mayo Clinic. Now that the permanent Department Chair has arrived, I can go back to my 'day job' of Chair of Clinical Microbiology and Director of the Clinical Parasitology laboratory. I anticipate being able to go back to regular posting again as well. 

So without further ado, here is our case this week, courtesy of Heather Morris, the Parasitology Technical Specialist in my laboratory. The following objects were found in a concentrated wet preparation of stool, and measure approximately 20 micrometers in diameter. No patient history is available. What is your identification?

Answer to Case 734

 Answer to the Parasite Case of the Week 734: Entamoeba coli cysts. 

As noted by Florida Fan and Mary Lois Smorenburg noted, these cysts can be easily recognized by their large size and number of nuclei (>4). These are the most definitive features of this organism and allow it to be differentiated from similar-appearing Entamoeba spp. such as E. histolytica. Other supportive features pointed out by Mary Lois Smorenburg and Dr. Satishkumar Krishnan are the eccentric karyosome within each nucleus is and the irregular splinter shaped chromatoid body.

Thanks again to Heather Morris for donating our first case of 2024!

Case of the Week 733

 This week's case is by Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following object was removed from a furuncular skin lesion in a patient with recent travel to Uganda. Once they were able to keep it still (!), Idzi captured the following photographs demonstrating all of the diagnostic features. What is your identification?

Answer to Case 733

 Answer to the Parasite Case of the Week 733: Cordylobia anthropophaga, myiasis causing fly larva. 

Florida Fan painted an accurate picture of this parasite with his vivid description: "The mango fly, aka Tumbu fly, lays eggs on human clothing hung to dry in the sun. The Man-Eating larvae hatching eats its way into the skin of its prey. The three sinuous slits are definite identification clues. Ironing the clothes dried outdoor kills the eggs and prevent a myasis infection. The video clearly exemplifies the voracious nature of The Beast." Very apt!

The adult female fly also commonly lays her eggs on sandy soil contaminated with urine and feces. The larvae hatch and may remain viable in the soil for 1-2 weeks while seeking a host. Upon contact with a suitable host, the larvae burrow into the skin of the host and develop for 8-12 days. They then emerge from the host and develop into pupae in the environment.

Extracted larvae can be identified based on the characteristics of their posterior spiracules, as well as their general body characteristics. There are several keys available for genus and species-level identification, including this older key from the CDC. Blaine Mathison and I also published a review on arthropod identification which you may find helpful. 

Along with this case, Idzi provided some great photos from previous posts for comparison:

Corydylobia rodhaina (Case of the Week 547):

Dermatobia hominis (Case of the Week 505):

Lastly, I'd encourage you to check out ITM's outstanding new podcast series entitled Transmission. Thanks again to Idzi and ITM for this great case!

Case of the Week 732

Welcome back to all of my US readers from the Thanksgiving holiday. Here is a fun case with the answer embedded - just listen to the audio with the video. Or if you'd prefer, keep the volume down and give your best guess on what you think this is! 

This case is donated by Dr. Jessica Lin and her colleague who is field physician in Tanzania.  The patient is a 4 year old boy with anal pruritus and history of passing worms from his anus. Several white-tan worms measuring ~5mm long were examined:

Answer to Case 732

 Answer to the Parasite Case of the Week 732: Enterobius vermicularis (pinworm) adult female. 

As noted by Florida Fan, "Well, this is a classic situation. Children by nature are very altruistic, sharing their prize possessions (e.g., M&M’s). The asymmetric eggs with a flat side and a convex side are commonly shared in this fashion." The appearance of the eggs is also called planoconvex or "D" shaped. Anonymous mentioned that the extensive uterine reproductive system of the fertilized female worm is often completely filled with with these eggs.

If you watched the video, you could see the movement of the eggs within the uterus, and appreciate the prominent lateral alae (arrows):

Thanks again to Jessica Lin and her team for providing this fun case! 

Case of the Week 731

 The following objects were seen in fluid aspirated from a cyst in the liver. Identification?

Some were still moving!

Answer to Case 731

Answer to the Parasite Case of the Week 731: Echinococcus sp. protoscolex. Hopefully you all got to look at it moving! Given that this is a single liver cyst, it would fit with E. granulosus. Correlation with radiologic and epidemiologic features would be helpful for confirmation.

Here are some of the key diagnostic features:

Case of the Week 730

 This week's case is generously donated by Idzi Potters and the Institute of Tropical Medicine, Antwerp.

The following were seen in used contact lens solution from a young woman with complaints of eye pain and blurry vision. The first two images are taken with light microscopy, and the third with phase-contrast microscopy. What is your diagnosis? Please describe the forms you are seeing.

Answer to Case 730

 Answer to the Parasite Case of the Week 730: Acanthamoeba keratitis.

As noted by Anonymous, the pictures are a perfect rendition of the “thorny” Acanthamoeba trophozoite and its polygonal cyst (acanth is New Latin, from Greek akanthos, from akantha thorn, spine). Cysts have 2 layers: a wrinkled outer layer (ectocyst) and inner layer (endocyst) that can be polygonal, spherical, hexagonal, or star-shaped.

Dr. Satishkumar Krishnam further described the trophozoite as "characterized by spine like pseudopodia (acanthopodia)." Chuck Blend noted that it looks like the first few seconds of a new proto-universe forming!

Thanks again to Idzi for this great case!