Inflammatory tinea pedis_0812 Derm Clinic
A Hispanic boy, aged 13 years, presented with vesicles and bullae on the medial aspects of the feet that had been present for several days. Occasional pruritus and pain with ambulation was reported.
The boy denied the use of any new topical prescription or OTC medications or products. The patient history was negative for new footwear. No personal or family history of atopic dermatitis were reported. The boy had been evaluated by his primary-care physician and started on oral griseofulvin one day prior to coming to the ED.
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The patient was diagnosed with inflammatory tinea pedis with large bullae. Affecting up to 70% of the population, tinea pedis is the most common dermatophyte infection.1 The development of infection depends on a number of factors within the host and in the local environment.
Immunocompromised individuals or those with decreased barrier function attributable to such conditions as diabetes mellitus or atopic dermatitis may be at increased risk for infection. Such local environmental factors as sweating and occlusive footwear can also increase the risk of developing tinea pedis. Because dermatophytes thrive in warm and moist environments, the incidence of tinea pedis is higher in athletes.2 Not surprisingly, this condition is uncommon in populations that do not wear shoes.3
Trichophyton rubrum and T. mentagrophytes are the most commonly implicated dermatophytes of tinea pedis.3 These dermatophytes are also common causes of tinea corporis and tinea cruris, so treatment for all three conditions is similar.
The four major clinical presentations of tinea pedis are interdigital, moccasin, inflammatory (vesicular/bullous), and ulcerative. Of these subtypes, interdigital is by far the most common, characterized by presentation with erythema, scaling, and fissure in the web spaces of the toes. Tinea pedis in a moccasin distribution presents with diffuse scaling on the plantar surfaces of the feet, a symptom that is often mistaken by patients for “dry skin.”
The inflammatory subtype is notable for vesicles and bullae on the medial aspects of the feet. Finally, ulcerative tinea pedis is usually seen in immunocompromised individuals and in diabetic patients with exacerbation of existing interdigital tinea pedis, leading to ulcers and erosions in web spaces.3
Complications from tinea pedis include bacterial superinfection and cellulitis. A thorough foot and toenail exam should be performed in individuals with recurrent cellulitis, especially those with diabetes, as tinea pedis can compromise the epidermal barrier, providing a portal of entry for bacteria.
The diagnosis of tinea pedis often can be made clinically. A comprehensive skin exam should be performed, focusing on such areas commonly infected by dermatophytes as the toenails, inguinal folds, axillae, buttocks, and web spaces of the toes.
When possible, the diagnosis should be confirmed by such noninvasive modalities as KOH examination and/or fungal culture. Scale from the leading edge of the plaque or roof of vesicles has the highest yield when searching for hyphael elements with KOH preparation under microscopy. If a biopsy is performed, a periodic acid-Schiff stain should be requested to better visualize hyphae in the stratum corneum.
The differential diagnosis of vesicles and bullae on the soles of the feet include acute contact dermatitis and dyshidrotic eczema. Because of the natural arch of the foot, contact dermatitis from shoes classically spares the instep. Contact dermatitis caused by topical medications often spares the web spaces, as it is unusual to apply medications in this area. Dyshidrotic eczema presents as extremely pruritic, deep-seated vesicles with “tapioca pudding-like” appearance.
If it is difficult to distinguish between these entities clinically, then a KOH examination, fungal culture, or biopsy should be obtained. The differential diagnosis for tinea pedis without vesicles or bullae includes psoriasis, juvenile plantar dermatosis, and secondary syphilis.
Topical medications are usually sufficient for treatment of tinea pedis. All topical medications should be used b.i.d. for two to six weeks. There is in vitro evidence that topical butenafine (Lotrimin Ultra) and topical terbinafine (Lamisil, Turbinex) are 10 to 100 times and two to 30 times more effective than azole antifungals against common dermatophytes, respectively.3 Because of this, many dermatologists prefer butenafine for the topical treatment of tinea pedis.
Nevertheless, more studies are needed to determine whether greater in vitro efficacy correlates with greater clinical efficacy in the treatment of tinea pedis. A recent systemic review found no significant difference between cure rates or side-effect profiles among the various topical antifungals.4 However, as this study pooled data from all tinea infections, no specific conclusions can be made regarding topical treatment of tinea pedis.
Indications for treatment of tinea pedis with oral antifungals include toenail involvement, widespread or severe disease, and/or resistance to topical antifungals. The duration of treatment for superficial tinea infections is two weeks. If there is evidence of toenail involvement, however, the patient should be treated for three months, as onychomycosis is a reservoir for future tinea infections.
In pediatric patients, griseofulvin is often the treatment of choice. Common side effects include GI complaints, rash, and headache. Hepatotoxicity has rarely been documented.
For adults with tinea pedis, terbinafine is the treatment of choice. The FDA recently approved a granule formulation of terbinafine that can be sprinkled on food. No baseline labs are necessary for treatment durations of fewer than six weeks. Side effects include diarrhea, taste disturbance, rash, and headache. Liver enzyme abnormalities (two times the upper limit of normal) may be seen after four to six weeks of therapy; therefore, if a prolonged course of treatment is expected, liver function tests should be obtained at baseline and after six weeks of therapy.
Since griseofulvin and terbinafine may have significant interactions with other medications, a careful drug reconciliation is mandatory prior to administration of either medication.5 There are two formulations of both griseofulvin and terbinafine, so attention is required to ensure proper dosing.
This patient’s presentation was most consistent with inflammatory tinea pedis, as he had notable bullae of vesicles and bullae on the medial instep of the bilateral feet. The key to clinical diagnosis was the scaling in all 10 interdigital spaces consistent with a fungal etiology.
A KOH examination could not be obtained, but a fungal culture was positive. The preliminary report of this fungal culture revealed the fungus Fusarium, which is a well-established cause of tinea pedis. The patient was continued on oral griseofulvin as prescribed by his primary-care physician with improvement at his two-week follow-up.
Audrey Chan, MD, is a first-year dermatology resident at Baylor College of Medicine in Houston.
- Masri-Fridling GD. Dermatophytosis of the feet. Dermatol Clin. 1996;14:33-40.
- Field LA, Adams BB. Tinea pedis in athletes. Int J Dermatol. 2008;47:485-492.
- Bolognia JL, Jorizzo JL, Rapini RP eds. Dermatology. 2nd ed. St. Louis, Mo.: Elsevier-Mosby; 2008:1144-1146, 1961-1967.
- Rotta I, Sanchez A, Gonçalves PR, et al. Efficacy and safety of topical antifungals in the treatment of dermatomycosis: a systematic review. Br J Dermatol. 2012;166:927-933.
- Wolverton SE. Comprehensive Dermatologic Drug Therapy. 2nd ed. Philadelphia, Pa.: Saunders Elsevier; 2007:86-90.