Tinea nigra (Pityriasis nigra)

Etiology

• Exophiala werneckii (Hortae werneckii)
• Stenella araguata

Epidemiology

• prevalence higher in tropics

Clinical manifestations

• dark lesions giving a spattered appearance
• lesions are most common on the palms of the hands
  • soles less frequently affected
• generally unilateral

* image Tinea nigra palmaris

Laboratory

• skin lesion scraping
  • direct microscopic examination on potassium hydroxide (10%) mount
    • brown branched septate hyphae
  • culture in Sabouraud agar
    • brownish black wet colonies after 1 month of inoculation at 21 C

Diagnostic procedures

• dermoscopy
  • nonmelanocytic pigmentation not respecting furrows & ridges
  • contrast with parallel ridge pattern seen in melanocytic lesions, in which pigmentation spares furrows

Differential diagnosis

• melanocytic nevus
• palmar lichen planus
• Cydnidae pigmentation
• melanosis of syphilis
• postinflammatory hyperpigmentation

Management

• topical azole antifungals & keratolytics (salicylic acid & urea) provide resolution within 2 months
• vigorous washing & scraping may be helpful

More general terms

• Tinea

Additional terms

• Exophiala werneckii; Cladosporium werneckii; Hortae werneckii
• stratum corneum (keratin {horny} layer)