The patient was given a diagnosis of vesicular (vesiculobullous) tinea pedis, based on the vesicles and bullae over the arch region of the foot. The arch is a typical location for vesiculobullous tinea pedis. There are 3 main types of tinea pedis: interdigital, moccasin distribution, and vesiculobullous (which is the least common type). Interdigital tinea pedis is the most common type and is typically seen between the fourth and fifth digits. The moccasin distribution tends to involve more erythema and scale—especially on the sides of the feet—giving the appearance of moccasins.
In general, tinea pedis is most commonly caused by Trichophyton rubrum. Other causative organisms include Trichophyton mentagrophytes and Epidermophyton floccosum. The vesiculobullous type of tinea pedis is usually caused by T mentagrophytes. The FP made this diagnosis clinically and did not perform a potassium hydroxide (KOH) preparation, as this type of tinea pedis has minimal scale and the dermatophyte may be harder to identify with the superficial scraping.
The FP prescribed 2 weeks of oral terbinafine 250 mg/d instead of relying on topical antifungal medicine because a better response can be expected with it. One month later, the vesiculobullous tinea pedis was fully resolved.
Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Usatine R, Reppa R. Tinea pedis. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013:799-804.
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