Are You Confident of the Diagnosis?
What you should be alert for in the history
There is a history of a stable or slowly growing single light-to-dark-brown macule, patch, or linear lesion on the palm or sole; rarely, there can be multiple lesions or lesions on the trunk. There may be a history of a preceding injury; contact exposure to wood, sewage, or compost; or a history of hyperhidrosis. Patients who do not live in a humid environment may give a history of travel to a tropical locale.
Characteristic findings on physical examination
The patch may range in shape from round to geometric, and is asymptomatic or occasionally pruritic (Figure 1).
Expected results of diagnostic studies
Dermoscopy of the lesion will reveal pigment that does not follow dermatoglyphs (Figure 2), scraping of the lesion with a No. 15 blade may remove portions of the lesion, and microscopic examination of the scrapings treated with 20% potassium hydroxide (KOH) will reveal pigmented branching hyphae and round spores.
Histopathology is rarely necessary, but biopsy with H&E staining may have acanthosis, hyperkeratosis, and a mild perivascular infiltrate; the periodic acid Schiff (PAS) stain will show hyphae in the stratum corneum (Figure 3).
Culture of skin scrapings or tissue on Saboraud at 25oC will grow mucoid black colonies at one week. PCR testing for the most common cause of tinea nigra, Hortaea werneckii, is available.
The most common differential diagnosis for tinea nigra is a melanocytic lesion (an acral lentiginous melanoma, junctional nevus, or lentigo). These entities can be differentiated from tinea nigra by dermoscopy, or by exam of scrapings of the lesion using KOH.
Skin staining with silver nitrate, postinflammatory hyperpigmentation, secondary syphilis, and Addison’s disease are also in the differential diagnosis, but should be able to be excluded by history, additional findings on physical exam, or by KOH exam.
Who is at Risk for Developing this Disease?
Otherwise healthy young men, women, and children who live in humid tropical environments are most at risk for developing tinea nigra. Hyperhidrosis of the palms or soles and exposure to soil, sewage, and compost are also frequently associated risk factors.
What is the Cause of the Disease?
Hortaea werneckii is a dematiaceous yeast that causes most cases of tinea nigra. It was formerly classified as Cladosporium werneckii, Exophalia werneckii, and Phaeoannellomyces werneckii. Less commonly, tinea nigra has been reported to be caused by another dematiaceous yeast, Stenella araguata.
The pigmented yeast lives in compost, soil, and trash, and traumatic inoculation of the fungus into the skin results in infection. The fungus is lipophilic and thrives in high salinity, thus it has an affinity for areas of the skin with high concentrations of eccrine glands. The infection is limited to the stratum corneum, where the fungus survives by digesting the lipids.
Systemic Implications and Complications
Tinea nigra in healthy patients is always a superficial infection limited to the stratum corneum. Very rarely, in severely immunosuppressed patients, specifically patients with neutropenia following treatment for acute leukemia, Hortaea werneckii has been isolated from blood cultures or internal organ abscesses. Cases of systemic infection with dematiaceous fungus are referred to as phaeohyphomycoses.
Generally, tinea nigra can be treated topically. In limited cases, the pigmented patch may be scraped off with a No. 15 scalpel or with repeated epidermal striping with adhesive tape given that it is confined to the stratum corneum.
Keratolytics, including salicylic acid, urea, and combinations of salicyclic acid and benzoic acid known as Whitfield’s ointment, have been reported to be effective.
Topical antifungals, including the imidazoles clotrimazole, ketoconazole, and miconazole, have all been reported to be effective when used for 2-4 weeks. Ciclopiroxolamine, terbinafine, and naftifine are also reported to be effective.
Oral griseofulvin has been reported to be ineffective, and generally oral therapy is neither necessary nor has it been reported to be effective.
Optimal Therapeutic Approach for this Disease
For small lesions, removal with a No. 15 blade or tape stripping may be the most direct approach. This may be a better approach than topical therapy in children who are likely to put their hands in their mouths.
Keratolytics and topical antifungals in gel or spray form may be better tolerated on the palms than creams.
If a patient gives a history of hyperhidrosis, drying agents such as aluminum chloride should be used in conjunction with antifungals or keratolytics.
Topical treatment has been effective in all reported cases. Treatment should be effective within 4 weeks, and if it is not, the diagnosis should be re-evaluated. Recurrence is rare.
Unusual Clinical Scenarios to Consider in Patient Management
Generally, topical therapy is successful and lesions do not recur. Pediatric patients can be managed in a way similar to adult patients.
What is the Evidence?
Perez, C, Colella, MT, Olaizola, C. “Tinea nigra: a report of twelve cases in Venezuela”. Mycopathologia. vol. 160. 2005. pp. 235-8. (A case series of twelve patients with tinea nigra from Venezuela reported clearing of the lesions within 1 to 2 weeks with treatment with a topical keratolytic compound made of benzoic acid, salicylic acid, glycerol, alcohol, and water)
Bonifaz, A, Badali, H, de Hoog, GS. “Tinea nigra by Hortaea werneckii, a report of 22 cases from Mexico”. Stud Mycol. vol. 61. 2008. pp. 77-82. (In a case series of twenty-two patients from Mexico, eleven patients were treated with a compound of salicyclic acid and benzoic acid, four with ketoconazole, four with bifonazole, two with terbinafine, and two patients were not treated with anything. Twenty-one patients were cured, including the two who were not treated, whose lesions resolved spontaneously within 2 months. The treated patients responded within 12-18 days, and the one patient who did not respond to the salicylic acid-benzoic acid compound did respond to a topical antifungal.)
Rosen, T, Lingappan, A. “Rapid treatment of tinea nigra palmaris by ciclopirox olamine gel 0.77%”. Skinmed. vol. 5. 2006. pp. 201-3. (Individual case of tinea nigra responding to ciclopiroxolamine gel in 3 days.)
Burke, WA. “Tinea nigra: treatment with topical ketoconazole”. Cutis. vol. 52. 1993. pp. 209-11. (Individual case of tinea nigra responding to topical ketoconazole)
Gupta, G, Burden, AD, Shankland, GS. “Tinea nigra secondary to Exophalia werneckii responding to itraconazole”. Br J Dermatol. vol. 137. 1997. pp. 483-4. (Individual case of tinea nigra responding to itraconazole)
Shannon, PL, Ramos-Caro, FA, Cosgrove, BF, Flowers, FP. “Treatment of tinea nigra with terbinafine”. Cutis. vol. 64. 1999. pp. 199-201. (Individual case of tinea nigra responding to terbinafine)
Copyright © 2017, 2013 Decision Support in Medicine, LLC. All rights reserved.
No sponsor or advertiser has participated in, approved or paid for the content provided by Decision Support in Medicine LLC. The Licensed Content is the property of and copyrighted by DSM.