CLINICAL HISTORY:

Signs and symptoms:  The patient reported a 5-year history of two brown spots on the left hand. Initially the lesions were blue and attributed to ink stains although the patient denied contact with any staining chemicals or dyes. The “spots” increased in size over a two-year period and changed from blue to brown in color. She denied recent travel and had no history of skin cancer or atypical nevi. Family history revealed a brother with a history of melanoma. Her medications included premarin and glucosamine and she denied any allergies.

Previous Treatment: 

Other information: 

PHYSICAL EXAM:

Two brown velvety irregularly pigmented patches on the palm of the left hand.

LABORATORY TESTS:

Pigmented hyphae present on KOH preparation of lesional scraping.

DERMATOHISTOPATHOLOGY:

High power depicting inconspicuous hyperpigmented hyphae within the stratum corneum. (H+E stain, 400x)


PAS stain highlighting fungal elements in the stratum corneum. (PAS stain, 400x)

DIFFERENTIAL DIAGNOSIS:

1.   Tinea nigra
2.   Melanocytic lesions: junctional nevi, lentigines, and melanoma
3.   Hyperpigmentation from exogenous chemical stains: silver nitrate, india ink
4.   Systemic disorders: Addison’s disease, tertiary syphilis, pinta and yaws
5.  

SCROLL DOWN FOR ANSWER AND DISCUSSION.

CORRECT DIAGNOSIS:

Tinea nigra

DISCUSSION:

Tinea nigra is a rare superficial fungal infection of the palmar and plantar stratum corneum. Currently identified as Exophiala phaeoannellomyces, this dermatophyte had a previous taxonomic designation of Exophiala werneckii. Other dematiaceous fungi have been linked with the disease, including Stenella araguata, although Exophilia phaeoannellomyces is considered the most common cause.
Tinea nigra infection clinically appears as mottled, brownish-black, velvety macules with fine scale arising on the palms, volar aspect of fingers, or soles. Lesions are asymptomatic and over time increase in size and darken in appearance.

Tinea nigra is most common in tropical regions such as South or Central America but has been reported in the United States particularly in Florida, Texas, and North Carolina. The fungus is ubiquitous to soil, sewage, or decaying vegetation. Infection occurs most commonly by inoculation, although rare human to human transmission has been described. Incubation time can range from weeks to years.

Diagnosis can be easily established by KOH examination of a lesional scraping. Brown to green hyphae and budding yeast cells are seen. Characteristically, hyphae are freely branching and septate, whereas yeast cells are single or paired and oval to spindle in shape.

Mycological isolation initially reveals yeast-like colonies that appear brown to shiny-black in color. As cultures age, filamentous colonies with peripheral aerial mycelium develop, creating a grayish-green appearance.

Biopsy typically yields subtle changes consisting of mild hyperkeratosis with a sparse dermal lymphocytic infiltrate. Exocytosis of neutrophils, typical of dermatophytosis, are not conspicuous features of this entity. Although pigmented spores and branched hyphae can be seen with high power scrutiny of the stratum corneum, these elements are more readily identified by GMS or PAS staining.

TREATMENT:

This patient began a three-week course of topical econazole and reported complete resolution without recurrence.

Topical treatment remains to be the primary management of Tinea nigra. Antifungals from the imidazole family (clotrimazole, miconazole, ketoconazole, sulconazole, econazole) are most effective. Treatment duration of at least 2 to 3 weeks is recommended.
Alternative therapies include shaving of the superficial epidermis with a no. 15 blade alone or in combination with topical keratolytics and antifungal preparations (Whitfield’s ointment, topical thiabendazole, and retinoic acid). Griseofulvin and topical tolnaftate have been ineffective in treatment along with oral terbinafine therapy; however, topical terbinafine was reported successful in clearing lesions.

REFERENCES:

1. Elgart ML (ed): Dermatologic clinics, vol. 14 Philadelphia, Saunders, 1996.

2. Fader RC, McGinnis MR: Infections caused by dematiaceous fungi Chromoblastomycosis and Phaeohyphomycosis. Infect Dis Clin North Am 1988; 2:925-938.

3. Rippon JW: Superficial infestations: Tinea nigra in medical mycology: The Pathologic Fungi and the Pathogenic Actinomyces, 3rd ed. Philadelphia, WB Saunders, 1988.

4. Babel DE, Pelachyk JM, Hurley JP: Tinea nigra masquerading as acral lentiginous melanoma. J Dermatol Surg Oncol 1986;12(5):502-504.

5. Sayegh-Carreno R, et al: Therapy of Tinea nigra plantaris. Int J Dermatol 1989; 28:46-48.

Additional Comment:

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