ESSENTIALS OF DIAGNOSIS
Most often presents with asymptomatic scaling.
May progress to fissuring or maceration in toe web spaces.
May be a portal of entry for bacteria causing lower extremity cellulitis.
Itching, burning, and stinging of interdigital web; scaling palms and soles; vesicles on soles in inflammatory cases.
KOH preparation or fungal culture of skin scapings is usually positive.
Tinea of the feet (athlete’s foot) is an extremely common acute or chronic dermatosis. Most infections are caused by Trichophyton species.
The presenting symptom may be itching, burning, or stinging. Pain may indicate secondary infection with complicating cellulitis. Interdigital tinea pedis is the most common predisposing cause of lower extremity cellulitis in healthy individuals. Regular examination of the feet of diabetic patients for evidence of scaling and fissuring and treatment of any identified tinea pedis may prevent complications. Tinea pedis has several presentations that vary with the location. On the sole and heel, tinea may appear as chronic noninflammatory scaling, occasionally with thickening and fissuring. This may extend over the sides of the feet in a “moccasin” distribution (Figure 6–12). The KOH preparation is usually positive. Tinea pedis often appears as a scaling or fissuring of the toe webs, often with maceration (Figure 6–13). As the web spaces become more macerated, the KOH preparation and fungal culture are less often positive because bacterial species begin to dominate. Finally, there may also be vesicles, bullae, or generalized exfoliation of the skin of the soles, or nail involvement in the form of discoloration, friability, and thickening of the nail plate.
Tinea pedis in the moccasin distribution. (Used, with permission, from Richard P. Usatine, MD, in Usatine RP, Smith MA, Mayeaux EJ Jr, Chumley H. The Color Atlas of Family Medicine, 2nd ed. McGraw-Hill, 2013.)
Tinea pedis in the interdigital space between fourth and fifth digits. The differential diagnosis includes a bacterial primary or secondary infection with gram-negative organisms. (Used, with permission, from Richard P. Usatine, MD, in Usatine RP, Smith MA, Mayeaux EJ Jr, Chumley H, Tysinger J. The Color Atlas of Family Medicine. McGraw-Hill, 2009.)
KOH and culture do not always demonstrate pathogenic fungi from macerated areas.
Another skin condition involving the same areas is interdigital erythrasma (use Wood light). Psoriasis may be a cause of chronic scaling on the palms or soles and may cause nail changes. Repeated fungal cultures should be negative, and the condition will not respond to antifungal therapy. Contact dermatitis will often involve the dorsal surfaces and will respond to topical or systemic corticosteroids (eFigure 6–34). Vesicular lesions should be differentiated from pompholyx (dyshidrosis) (eFigure 6–35) and scabies (eFigure 6–36) by proper scraping of the roofs of individual vesicles. Rarely, gram-negative organisms may cause toe web infections, manifested as an acute erosive flare of interdigital disease. This entity is treated with aluminum salts and imidazole antifungal agents or ciclopirox. Candida may also cause erosive interdigital disease.
Allergic contact dermatitis due to nickel. A chronic nature is suggested by the scaling and thickened skin. (Used, with permission, from R Odom, MD.)
Pompholyx: classic “tapioca” vesicles may be intensely pruritic leading to scaling and fissuring in advanced cases. (Used, with permission, from S Goldstein, MD.)
Typical site for excoriated, vesiculopustular lesions due to scabies. (Used, with permission, from S Goldstein, MD.)
The essential factor in prevention is personal hygiene. Wear open-toed sandals if possible. Use of sandals in community showers and bathing places is often recommended, though the effectiveness of this practice has not been studied. Careful drying between the toes after showering is essential. A hair dryer used on low setting may be helpful. Socks should be changed frequently, and absorbent nonsynthetic socks are preferred. Apply dusting and drying powders as necessary. The use of powders containing antifungal agents (eg, Zeasorb-AF) or long-term use of antifungal creams may prevent recurrences of tinea pedis.
Treat with aluminum subacetate solution soaks for 20 minutes twice daily. Broad-spectrum antifungal creams and solutions (containing imidazoles or ciclopirox) (Table 6–2) will help combat diphtheroids and other gram-positive organisms present at this stage and alone may be adequate therapy. If topical imidazoles fail, 1 week of once-daily topical allylamine treatment (terbinafine or butenafine) will often result in clearing.
Use any of the antifungal agents listed in Table 6–2. The addition of urea 10–20% lotion or cream may increase the efficacy of topical treatments in thick (“moccasin”) tinea of the soles.
Itraconazole, 200 mg orally daily for 2 weeks or 400 mg daily for 1 week, or terbinafine, 250 mg orally daily for 2–4 weeks, may be used in refractory cases. If the infection is cleared by systemic therapy, the patient should be encouraged to begin maintenance with topical therapy, since recurrence is common.
For many individuals, tinea pedis is a chronic affliction, temporarily cleared by therapy only to recur.
et al. Characteristics, associated diseases, and management of gram-negative toe-web infection: a French experience. Acta Derm Venereol. 2019 Nov 1;99(12):1121–6.
et al. Expert Consensus on The Management of Dermatophytosis in India (ECTODERM India). BMC Dermatol. 2018 Jul 24;18(1):6.