Malignant Melanoma is a high mortality neoplasm. The involvement of the nail apparatus is rare, with only 2 out of 3 patients seeking medical attention as the result of recent nail melanocytic lesions. This results in late diagnosis and a prognosis worse than cutaneous melanoma. We report a female, presenting with ulcerative lesions with clinical and laboratory features compatible with leishmaniasis. On return after treatment initiation a longitudinal melanonychia was observed on her first right finger. Biopsy of the nail matrix was performed. Histopathology was compatible with melanoma in situ. Longitudinal melanonychia is not a specific sign for melanoma and it is important that the dermatologist should identify the suspect lesions correctly. The incidental diagnosis of nail melanoma in situ in our case significantly impacted the patient's survival.
