Saturday, February 18, 2017

Answer to Case 435

Wow, this case generated a lot of interest, with requests for the answer when I didn't post yesterday. My apologies for leaving you all hanging!

This is a case of a non-parasitic fiber that had been transcutaneously implanted and migrated under the skin due to physical pressure (i.e. walking). Although the presentation was suggestive of a cutaneous parasitic infection such as cutaneous larva migrans (CLM), the length of the object and dark color were not consistent with any human or zoonotic parasite. Several readers pointed out specifically that the larvae that cause CLM are microscopic and therefore would not be visible to the naked eye. Also, the path formed by a migrating worm would be more serpiginous rather than the semi-lunar pattern observed here. Other subcutaneous or intra-epidermal/dermal worms such as Loa loa, zoonotic microfilariae, and Dracunculus medinensis were also suggested but rightly discarded by readers because of the size and color of this object. There is no parasite, to my knowledge, that would have this appearance and be present in this location in human skin.

One intriguing suggestion was that this was cutaneous pili migrans (CPM) - an excellent thought. CPM is a phenomenon in which a hair grows within the skin rather than up and out of the skin, and is seen as long dark object just below the skin's surface. This is most common on hair-bearing regions of the body and would be unusual on the sole of the foot. However, removal of the object would be required to rule out  CPM. Therefore, this is exactly what we did. Here are photographs of the object that we removed (cut in half):

As you can see, it looks to be a synthetic fiber and not any type of worm. It was extremely resilient, and while bendable, did not easily break. Just for fun (and because I knew you would all want to know), we analyzed the fiber using infrared spectrum analysis, which showed it to be most consistent with azlon, a synthetic fiber commonly used to make clothing and household objects.

Thanks again to Emily Hall for donating this fascinating case!

7 comments:

Zachary Telfer said...

I guess there should be a name for the condition. I vote Cutaneous filum migrans. Thanks for the great case.

Ulises Rojo said...

Very interesting case, it kind of reminded me of delusional parasitosis. Thank you for your work!

Dr. Bhushan said...

I was close enough

Bobbi Pritt said...

In speaking with my dermatology colleagues, I've found out that there is such a thing as "Teddy bear granuloma". With this phenomenon, fibers from a stuffed toy are accidentally inoculated into the skin of a child, much the way the fiber in this case is. Interesting!

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Gina Chiri-Osmond said...

So, Dr. Pritt, you're basically saying that this fiber from clothing or a household object lodged itself into the baby's foot--and then it slowly got completely stuck within the foot? Or did it lodge itself in the baby's body somewhere else and then slowly make its way DOWN to the foot? Either way, how often does something like that happen? And could a tiny fiber like that harm a person? Thanks and love your case studies, Gina.

Bobbi Pritt said...

Good question Gina. From our understanding, the object penetrated the skin of the foot, much like a splinter would. Because it was so slender and was on the ball of the foot, we believe in migrated in a semilunar pattern due to pressure from walking. Make sense?