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 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):
The following objects were seen in fluid aspirated from a cyst in the liver. Identification?
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:
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 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!
This week's case was generously donated by Drs. Jacob Rattin, Anisha Misra, and Hannah Wang, and originally identified by Marissa Roberts. The following objects were seen on a trichrome-stained stool specimen and measure approximately 15 micrometers in length. What is your identification?
Answer to the Parasite Case of the Week 729: Trophozoites of Chilomastix mesnili
Below is an answer written by Dr. Jacob Rattin (@EternalStudying):
This non-pathogenic flagellate has pear-shaped trophozoites that are 6 – 24 μm long with a longitudinal spiral groove running along the body (not seen in this specimen). If visualized in a fresh prep, the motility may allow the spiral groove to be seen as the organism turns (see Case 475). The trophozoite has one nucleus (arrowhead), usually at the anterior end, with an eccentric karyosome and a cytostome (oral groove) close by. The posterior end tapers to a point (arrow).
Differentiating C. mesnili trophozoites from other non-pathogenic flagellates such as Enteromonas hominis, Pentatrichomonas hominis, and Retortamonas intestinalis can be quite difficult. Thankfully, these organisms are non-pathogenic. However, the following features may be useful in teasing apart these fun flagellates!
Enteromonas hominis trophozoites measure 5 – 7 µm long with one nucleus and three anterior flagella and one posterior flagellum. It has a single nucleus with a large karyosome. There is no cytostome which helps to differentiate it from C. mesnili.
Retortamonas intestinalis are 4 – 10 µm long with an ovoid trophozoite form with a cytostome at the anterior half that is bordered by a fibril. The single nucleus is at the anterior end and has a small karyosome.
Pentatrichomonas hominis. The trophozoites are pyriform in shape, measuring 6 – 20 µm long. They have five flagella, with four directed anteriorly and a fifth directed posteriorly. The fifth flagellum forms the outer edge of an undulating membrane and projects beyond the posterior. A single nucleus is at the anterior end and contains a small karyosome.
Thanks again to Dr. Rattin for taking on the non-pathogenic flagellates! I'm sure you'll agree that he did an excellent job. Thanks also to the laboratory technologist, Marissa Roberts, who took these photos, and to Dr. Anisha Misra at the Cleveland Clinic for her scientific oversight.
