Pitted Keratolysis

Pitted keratolysis, also known as keratolysis plantare sulcatum or ringed keratolysis.

is a Superficial bacterial skin infection.

Characterized by crater-like pits on the skin and often accompanied by a malodorous smell.

Primarily affects pressure-bearing areas on the soles of the feet; rare occurrences on the palms.

Prevalence and Risk Groups

• Gender Prevalence: More common in men than in women.
• Age Group: Can affect all age groups.
• Occupations at Risk:
  • Athletes, industrial workers, miners.
  • Farmers, sailors, fishermen.
  • Military personnel.
  • Occupations with constant wet feet exposure (e.g., paddy field workers, boatmen).

Risk Factors

• Hyperhidrosis: Excessive sweating of hands and feet.
• Keratoderma: Thickened skin on palms and soles.
• Footwear: Prolonged use of occlusive footwear like vinyl or rubber boots.
• Other Factors: Diabetes mellitus, poor foot hygiene, hot and humid weather conditions, obesity, immunodeficiency.

Causative Agents

• Bacteria Involved: Corynebacteria, Dermatophilus congolensis, Kytococcus sedentarius, Actinomyces, Streptomyces.
• Bacterial Activity: These bacteria proliferate in moist, warm conditions, producing protease enzymes that degrade the stratum corneum, forming pits. The odour is due to sulfur compounds produced by the bacteria.

Clinical Features

• Symptomatology: Often asymptomatic; symptoms can include pruritus and pain during walking.
• Physical Signs:
  • Pits on the stratum corneum, typically 1–3mm in size.
  • Pits may coalesce into irregular erosions or sulci.
  • Some pits may appear brown, giving the impression of dirty feet.
  • Pits are more pronounced when feet are wet.
• Associated Features: Hyperhidrosis, slimy skin texture, malodorous feet.
• Variants: Painful plaque-like variant, large crateriform depressions, corynebacterial triad.

Impact on Different Skin Types

• Skin Types Affected: Seen in patients of all skin types, presenting similarly in various sizes and colors.

Complications

• Psychosocial Impact: Foot odour can have a significant social and psychological effect.
• Functional Limitations: Symptomatic pitted keratolysis can limit mobility and function.
• Mortality: No direct mortality associated with pitted keratolysis.

Diagnosis

• Method: Primarily clinical, based on distinctive appearance and malodour.
• Additional Examinations: Wood lamp examination, skin scrapings to rule out fungal infections, skin biopsy if uncertain.
• Cultures: Rarely used but may identify causative organisms.

Differential Diagnosis

• Conditions to Differentiate From: Basal cell nevus syndrome, focal acral hyperkeratosis, keratolysis exfoliativa, plantar warts, tinea pedis.

Treatment

• General Measures: Emphasizing foot hygiene, avoiding occlusive footwear, using absorbent socks, proper washing of feet and socks, antiperspirant use, avoiding shared footwear, managing hyperhidrosis.
• Specific Measures:
  • Topical Antibiotics: Clindamycin, erythromycin, mupirocin, fusidic acid (applied twice daily for 2–4 weeks).
  • Other Agents: Benzoyl peroxide (antimicrobial with keratolytic properties), potentially in combination with other topical antibiotics.
  • Oral Antibiotics: For refractory cases, options include clindamycin, erythromycin, tetracyclines.

Outcome

• Without Treatment: Possibility of years-long duration with spontaneous remission or exacerbation.
• With Treatment: Typically resolves in 2–4 weeks.