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Tinea nigra (Pityriasis nigra)
Etiology:
- Exophiala werneckii (Hortae werneckii)
- Stenella araguata
Epidemiology:
- prevalence higher in tropics
Clinical manifestations:
1) dark lesions giving a spattered appearance
2) lesions are most common on the palms of the hands
- soles less frequently affected
3) generally unilateral
* image Tinea nigra palmaris [2]
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
Special laboratory:
- 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
Related
Exophiala werneckii; Cladosporium werneckii; Hortae werneckii
stratum corneum (keratin {horny} layer)
General
Tinea
References
- Stedman's Medical Dictionary 26th ed, Williams &
Wilkins, Baltimore, 1995
- Saraswat N, Tripathy DM, Kumar S
Images in Dermatology: Tinea Nigra Palmaris
JAMA Dermatol. 2022;158(12):1439. Ot 26
PMID: 36287580
https://jamanetwork.com/journals/jamadermatology/fullarticle/2797841