Tinea Nigra Clinical Presentation

Generally, patients with tinea nigra are asymptomatic. Rarely, pruritus may be reported. The absence of any discomfort often delays the patient's decision to seek medical advice.

Patients who live in the inland areas of the United States generally report a history of foreign travel, most often to the Caribbean islands. In addition, patients may have acquired this infection while visiting the tropical regions of Asia or Africa. Those who reside in the coastal regions do not necessarily report any travel outside of the United States.

Uezato et al^[10] reported a case of tinea nigra palmaris from Okinawa, Japan on the left palm of a 13-year-old girl, who had noticed the pigmented, asymptomatic macule on her left palm approximately 4-5 years prior to presentation. She stated the lesion became lighter after a bath and darkened some time later. Physical examination revealed a 4 X 5-cm, dark brown, and irregularly shaped macule.

Histological findings were reported as follows: "Direct potassium hydroxide (KOH) microscopic examination from skin scrapings revealed branched brown hyphae with light brown septa. A fungal culture on Sabouraud's agar media produced wet, medium brown, yeast-like colonies, the surface of which later became black and shiny. A slide culture disclosed light brown, elliptic or peanut-shaped conidia comprised of one to two ampullaceous cells. Scanning electron microscopic examination of the conidia showed both annellation [sic] conidia with lunate bud scars and sympodial conidiogenesis."

DNA was extracted from separately cultured fungi, and polymerase chain reaction with primers specific to H werneckii was performed; results showed positive bands. Direct sequencing was performed with the DNA segments from the positive bands. Type C H werneckii was determined to be the causative fungus, based on the base sequences obtained, and tinea nigra due to H werneckii was diagnosed.

Tinea nigra is characterized by the presence of a painless brown-to-black macule, as shown in the image below. The macule appears insidiously as a small dark spot.

Hyperpigmentation of the macule ranges from light brown to black discoloration, resembling silver nitrate or India ink stains. The borders are typically discrete. The pigmentary change may appear mottled or velvety.

The lesions are typically solitary, although more than one lesion can be present. Solitary lesions are typically located on the palmar surfaces of the hands or plantar surfaces of the feet, and they may extend to the fingers or toes, respectively. Other areas of the body, such as the neck and chest wall, are more rarely affected.

The shape of the lesion varies, and they may appear ovoid, round, or irregular. The lesion slowly grows over weeks to months. The size may range from a few millimeters to several centimeters in diameter, depending on the duration of the infection.

Other physical findings, such as erythema or induration, are absent. Rarely, scaling is present. Dermoscopic examination may facilitate the in vivo diagnosis of tinea nigra.^[11] Manual and digital dermatoscopic images show irregularly distributed dark brown-pigmented dots with a filamentous aspect.^[12]

Although tinea nigra is often easily diagnosed on clinical grounds alone,^[13] the use of dermoscopy for palmar or plantar pigmentation may enhance the recognition of tinea nigra.^[14] Characteristic features evident on dermoscopy are superficial fine, wispy, light-brown strands forming a reticularlike patch with a uniform brown color. These strands do not follow the furrows and ridges normally observed in this skin.

Tinea nigra is due to infection by the fungus, P werneckii, which is classified in the family Dematiaceae, class Hyphomycetes, phylum Deuteromycota. Infection occurs after inoculation subsequent to trauma. The dermatomycosis tends to occur in areas with an increased concentration of eccrine sweat glands. Hyperhidrosis appears to be a risk factor for this disease.