How To Detect And Treat Tinea Pedis

By Barry Blass, DPM

   Fungal infections of the foot represent the fourth most common problem that we see in podiatric practice.1 Approximately 26.5 million people are affected annually.2 Nearly half of these people will suffer from multiple episodes for years. Treatment varies from home remedies and OTC preparations to a large variety of topical and oral medications. While tinea pedis is certainly is not the most challenging condition we treat, eliminating a longstanding, annoying and embarrassing condition can make the practitioner a hero in the eyes of his or her patient.

   I will leave the in-depth discussion of the categories of tinea infections of the foot to the dermatology textbooks. However, as a brief reminder, there are four basic presentations.

   Chronic squamous or papulosquamous tinea presents with dry, thick scales, frequently with fissuring on the plantar surface. The classical presentation is in a moccasin-type distribution. Interdigital tinea presents with maceration, scaling and itching between the toes. It frequently spreads to the plantar surface proximal to the web spaces. Acute vesicular or vesiculobullous tinea usually appears in non-weightbearing areas such as the longitudinal arch. It usually displays small vesicles and bulla on erythematous bases. Acute ulcerative tinea classically involves larger areas with desquamation of layers of tissue, foul odor and drainage.

   Although all tineas can lead to secondary infection, the acute ulcerative tinea is the most likely presentation to do so. This is a matter of increased concern for patients with diabetes, those with vascular disease and immunocompromised individuals.

How Diagnosis Of The Condition Has Evolved Over The Years

   When I was a student, I recall spending hours peering into a microscope looking for hyphae. We would take a scraping from the involved area and dissolve it in a dilute solution of potassium hydroxide. After the chemical dissolved the epithelial tissue, we examined the specimen for evidence of fungal organisms. Although we were always elated when we found those strands and buds, the search was not always easy. In many cases, obvious fungal infections eluded this KOH technique both in the hands of students and many clinical laboratories. Was the collection faulty or was the observer not tenacious enough? I do not know.

   As I started to visit podiatry offices and as I later discovered in my own office, it was common to have rows of bottles of culture media with an array of colors and contents that rivaled the neglected refrigerators of college students. Practitioners ordered DTM (dermatophyte test media) tests by the dozens. Not only did the DTM change color from orange to red in the presence of dermatophytes, the DTM also came with a handy color chart that guided the practitioner through a specific diagnosis of the causative organism. For years, Medicare mandated the testing for various CPT codes and insurance companies paid for the work. We had never heard of the Clinical Laboratory Improvement Amendment (CLIA) and our staff could handle most of the task.

   I no longer see young practitioners listing a microscope as essential in their list of equipment priorities. Although the bottles of media are not gone, their numbers have decreased drastically with an increase in the paperwork required to use them. In many cases, the practitioner relies on his or her clinical knowledge to make the diagnosis. When specific proof is needed, the PAS stain is now the preferred test. However, when one sends a sample to an outside lab, it is a good idea to ensure the lab has individuals well versed in the test. The PAS stain is rapid (unlike DTM), dependable (unlike KOH) and universally well accepted. With the broad spectrum of the medications I will discuss, it has become less important to identify the specific species.

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