Tinea nigra on the fingers

Description

A 57-year-old man presented to the emergency room, with sudden onset of brown spots on his fingers. He denied any trauma or tattoos in these areas, had not travelled to tropical or subtropical regions, and did not have a history of any systemic disease and did not use drugs. He was a farmer and had close contact with water and plants. On dermatological examination, there were light brown macules on the second, third and forth fingers of his left hand (figure 1A, B). Basic laboratory tests were normal. Arterial duplex ultrasound of this extremity was normal, ruling out stenosis. We performed 15% potassium hydroxide (KOH) examination with scraps from the lesion, which revealed brownish septate hyphae with budding pigmented yeast-like cells. On dermoscopic examination, light brown reticulate patches formed by superficial fine, wispy strands that did not follow the furrows and ridges were seen (figure 2). We diagnosed the patient as having tinea nigra, for which isoconazole nitrate cream (Travogen) was started. After 2 weeks, the lesions almost completely disappeared (figure 1C, D).

Figure 1.

(A and B) Light brown macules on the second, third and fourth fingers of the left hand. (C and D) The appearance of the second, third and fourth fingers 2 weeks after treatment.

Figure 2.

Dermoscopically, light brown reticulate patches formed of superficial fine, wispy strands that do not follow the furrows and ridges (original magnification ×10).

Tinea nigra is a rare superficial mycosis, seen particularly in tropical regions, and caused by Hortaea werneckii. Hyperhydrosis and living in coastal regions or hypersaline environments are predisposing factors.¹ The condition is characterised by pigmented, macular patches localised on the palms or soles, which potentially mimic pigmentary lesions such as melanoma, especially when presenting as a solitary lesion.² Once suspected, it can easily be diagnosed with a simple KOH and dermoscopic examination or culture. Thus, the patient avoids unnecessary interventions such as biopsy.

Learning points.

• Tinea nigra usually presents with asymptomatic, pigmented, macular patches on the palms or soles, mimicking pigmentary lesions such as melanoma, especially when presenting as a solitary lesion.

• Tinea nigra may also be seen in non-tropical regions and on unusual body parts such as fingers, as in our case, rather than being limited to the palms and soles.

• It is easy to diagnose and treat tinea nigra when it is kept in the differential diagnosis. Thus, the patient avoids unnecessary interventions such as biopsy.