Pitted keratolysis is a superficial bacterial infection of the stratum corneum on weight-bearing areas of the soles (and less commonly palms) characterized by malodor and discrete crateriform pits. It is caused by gram-positive bacteria (Corynebacterium, Kytococcus, Dermatophilus) that produce keratin-degrading proteases. It is common in individuals with hyperhidrosis and occlusive footwear. Treatment involves antibacterial agents, antiperspirants, and moisture control.
Epidemiology and Risk Factors
- Young adults, athletes, military personnel, workers wearing occlusive shoes/boots.
- Hyperhidrosis, hot/humid environments, prolonged occlusion, poor sock/shoe ventilation.
Clinical Features
- Malodorous soles with multiple superficial pits (1–3 mm) on pressure-bearing areas (forefoot, heel); pits may coalesce into erosions.
- Surrounding skin may be white and macerated; minimal inflammation or pain; burning or tenderness in some.
Differential Diagnosis
- Tinea pedis (interdigital maceration with scale; KOH positive), plantar warts (interrupt dermatoglyphics; thrombosed capillaries), keratolysis exfoliativa, erythrasma, punctate palmoplantar keratoderma.
Diagnosis
- Clinical. KOH microscopy to exclude tinea if scaling present.
- Wood’s lamp may show faint coral-red or none (variable).
- Gram stain from scrapings can reveal gram-positive coccobacilli/filamentous organisms; culture seldom necessary.
Management
- Antibacterial therapy
- Topical: clindamycin 1% solution/lotion bid, erythromycin 2% gel/solution bid, fusidic acid (where available), mupirocin bid. Continue 2–4 weeks.
- Benzoyl peroxide 5–10% wash daily reduces bacterial load and helps with odor.
- Oral macrolides (erythromycin/azithromycin) reserved for refractory or extensive cases.
- Sweat and moisture control
- Aluminum chloride hexahydrate 20% solution nightly (then maintenance 2–3 times weekly) to treat hyperhidrosis.
- Alternate footwear to allow drying; moisture-wicking socks; consider antifungal/antibacterial powders.
- Foot hygiene: daily washing and thorough drying, especially between toes; avoid barefoot in communal showers if coexistent tinea.
- Adjuncts
- Keratolytics (urea 20–40%, salicylic acid 6%) to reduce hyperkeratosis if present.
- In recalcitrant hyperhidrosis: iontophoresis or botulinum toxin injections to soles (specialist setting).
- Prognosis and Recurrence
- Excellent with treatment; recurrence common if hyperhidrosis/occlusion persist—maintenance measures are key.
References (recent guidelines and key reviews)
- Superficial bacterial plantar infections and pitted keratolysis management, 2021–2024.
- Comparative efficacy of topical antibiotics and benzoyl peroxide, 2021–2023.
- Hyperhidrosis treatments in foot infections, 2022–2024.