When discussing tinea pedis (TP), there are a few important topics that need to be covered:

1. Tinea pedis is a fungal infection that should be treated with an antifungal.
2. Untreated TP can lead to serious complications such as bacterial infections.
3. TP is frequently misdiagnosed as “dry skin”.
4. TP and onychomycosis are inexorably linked. You can’t have one without the other.
5. There are many different treatments in various formulations, both topical and oral, that can be used.

In this necessarily brief eZine format, I can only touch on a few of these. I direct you to the full PRESENT lecture on tinea pedis for a more in depth discussion.

The natural history of onychomycosis is thought to begin as a fungal infection of the skin of the foot. Because of some trauma that breaks the hyponichial seal at the distal end of the toe, the fungus is able to migrate under the nail and infect the nail bed stratum corneum, thus leading to classic distal subungual onychomycosis. Furthermore, you cannot treat one without treating the other. If you treat the nail with a topical drug but don’t treat the skin, the TP can then reinfect the nail bed, causing a recurrence. Likewise, if you treat the TP without treating the nail, the onychomycosis can then reinfect the skin.

This close relationship between TP and onychomycosis first really became evident when we started using oral antifungal agents such as terbinafine or itraconazole. The patient would be instructed to return in 4-6 weeks for blood work. Of course, the nails were mostly unchanged at that time, but the skin was remarkably clear, even if the skin had not been diagnosed as being infected. Over time, the nails would begin to clear and the skin stayed infection free.

This early skin clearance while using oral antifungals brings up another important topic listed above; the frequent misdiagnosis of TP as simple “xerosis” or “dry skin”. In the above scenario, it was not uncommon for the patient to be incredibly excited at that initial return visit. The patient would exclaim “Doc, I’ve been using moisturizers for years on my feet, but now my skin has never looked so good!” Examine the skin closely. If the dryness is only on the plantar aspect or in a moccasin distribution, yet the dorsal skin remains relatively normal looking, it doesn’t matter if there are the classic serpiginous or annular lesions present…it is tinea pedis until proven otherwise. Obtain a good scraping and send to a reputable laboratory for KOH, PAS or fungal cultures.