pitted keratolysis

Etiology

• Corynebacterium species (major cause)
• Kytococcus sedentarius (formerly Micrococcus sedentarius)
• Dermtaophilus congolensis
• Actinomyces
• Streptomyces
• hyperhidrosis of the feet predisposes
  • warmth, mosture, occlusion are risk factors

Epidemiology

• affects mostly young adults
• affects males >> females

Pathology

• thickening of plantar fascia

Clinical manifestations

• manifests as scale & pitting of the skin surface
• pits in stratum corneum of plantar foot 1-8 mm in diameter
• pits may be discrete, but more often become confluent forming large areas of eroded stratum corneum
• involved areas are white when stratum corneum is fully hydrated
• symmetric or asymmetric involvement of both feet
• distribution:
  • toe webs, balls or heel of foot in contact with shoe
  • lesions on pressure-bearing locations
• generally asymptomatic, but may be associated with itching, burning or tenderness
• foot odor (malodorous)
• hyperhidrosis

* images

Laboratory

• no hyphae in 10% KOH preparations from skin scrapings
• Wood's lamp: negative for coral-red fluorescence (erythrasma)
• culture (rule out Staphylococcus aureus, group A streptococcus, Pseudomonas aeruginosa)

Differential diagnosis

• tinea pedis
• Candida intertrigo
• erythrasma
  • red-brown plaques in the groin, crural folds, gluteal folds, axillae,
    • less commonly in the interdigital or inframammary regions
  • skin often has a thin, wrinkled appearance similar to cigarette paper
  • soft coral red fluorescence under Woods lamp
• gram-negative bacillus web infection
• plantar wart
  • exophytic papules on the soles of the feet
  • hyperkeratotic debris often covers the tops of the lesions
  • after scraping lesion surface, black or red dots (thrombosed capillaries) become visible

Management

• prophylaxis
  • wash with lather from benzoyl peroxide soap bar
  • antiperspirants (AlCl3)
• treatment
  • benzoyl peroxide: apply daily
  • topical erythromycin: apply daily

More general terms

• keratolysis
• bacterial infection
• skin infection

Additional terms

• nail pitting