Tinea Nigra: Clinical and Diagnostic Guidance.

Tinea nigra is a rare superficial fungal infection characterized by asymptomatic, unilateral, well-defined brown to black macules predominantly affecting the palms and soles. Diagnosis is often challenging due to its rarity and resemblance to other pigmented lesions. This report presents a clinical case, a diagnostic algorithm, and treatment recommendations, emphasizing the role of thorough examination and questioning. We describe the case of a 64-year-old woman of Amerindian (Maya) heritage from Yucatan, Mexico, who presented with a three-month history of a slowly growing dark spot on her left palm. The lesion was asymptomatic, non-scaling, and non-palpable. Palmar skin scrapings, prepared with KOH, revealed pigmented yeast and hyphae, leading to a diagnosis of tinea nigra. Following treatment with topical ketoconazole, the patient's lesions completely resolved at the one-month follow-up. The cultivation of scales confirmed the presence of Hortaea werneckii. Our findings highlight the importance of considering tinea nigra in the differential diagnosis of pigmented lesions on acral surfaces. We propose a diagnostic algorithm to aid healthcare professionals in recognizing this uncommon condition and recommend treatment protocols that effectively resolve the infection within two weeks. This case underscores the necessity for increased awareness and accurate diagnosis of tinea nigra, particularly in non-endemic regions.