Answer to Case 425

Answer: Enterobius vermicularis

This was a challenging case, since we aren't given the size of the worms, their movement in the video precluded close examination, and the histologic features were somewhat distorted.

While I had initially thought of E. vermicularis, I must admit that, with further evaluation, I had convinced myself that the "anterior end" was embedded into the intestinal mucosa, making me instead suspect Trichuris trichiura (arrow below). 

Thankfully, my parasite pals, Blaine Mathison and Dr. Marc Courturier, provided a valuable second opinion. After our discussion, I realized that the end shown above was actually the partially clear posterior that we often see with female pinworms, like in the image below (arrow):

Blaine also pointed out that the tall musculature seen with T. trichiura was lacking in the biopsy specimen, thus ruling out that diagnosis. Also, he noted that he has occasionally seen the lateral alae take on a similarly distorted appearance in biopsy specimens: 

Therefore, the lessons for me on this case were 1.) it's possible to "overthink" yourself out of the correct diagnosis and 2.) reach out to your parasite pals when you are in need of a second opinion. 

We have built a strong community of parasitologists here through this blog, and I thank all of you for your ongoing support. Happy Holidays!