Abstract
INTRODUCTION: Nail unit melanoma is a rare and potentially aggressive variant of acral lentiginous melanoma. Diagnosing amelanotic variants can be particularly challenging due to the absence of typical pigmentation. Here, we report a case of chronic onychodystrophy revealing amelanotic nail unit melanoma. CASE PRESENTATION: A 48-year-old Moroccan patient presented with chronic persistent monodactylic nail dystrophy. Dermoscopy showed subungual hyperkeratosis with an atypical vascular pattern but no pigmented structures. A biopsy of the nail unit confirmed amelanotic melanoma. Staging (PET scan, lymph node ultrasound, and bone CT) excluded metastases. Surgical management led to metacarpophalangeal amputation of the thumb. CONCLUSION: This case underscores the need to consider amelanotic melanoma in patients with atypical or persistent nail lesions. Early recognition and prompt treatment can significantly affect prognosis. Monodactylous involvement with nail dystrophy, including nail plate destruction, should lead to a nail biopsy for an early and accurate diagnosis.