[Mucinous nevus of late onset]. / Nævus mucineux de révélation tardive.

INTRODUCTION: Mucinous nevus is a rare disease characterized by mucin deposits in the dermis, with only 23 cases reported to date. It belongs to the connective tissue nevus family and is characterized by dermal mucin deposits. Two histological subtypes have been described: pure mucinous dermal nevus (connective tissue nevus of the proteoglycan [CTNP]) and combined mucinous nevus (combined CTNP) associating epidermal nevus with dermal mucin deposits. Lesions generally appear in childhood or early adulthood. We report herein the case of a 59-year-old man with a symptomatic lesion. OBSERVATION: A 59-year-old man consulted for unilateral lesions occurring linearly along the Blaschko line on the right lower limb, composed of brown verrucous papules, which started at the age of 50. The patient complained of itching caused by friction from clothes. Histological examination of a papule highlighted an acanthotic epidermis, with elongation of rete ridges and mucin deposits in the dermis showing uptake of alcian blue stain. The clinicopathological analysis enabled diagnosis of combined CTNP. We treated this nevus by surgical dermabrasion and observed a slight and cosmetically acceptable scar. DISCUSSION: To our knowledge, our patient is the oldest reported to date and the only one to have complained of symptoms. Our review of the literature highlights the importance of skin biopsy to guide aesthetic or symptomatic treatment. CO2 laser and dermabrasion are recommended for combined CTNP as they treat the epidermal component with low risk of secondary scarring. However, these techniques should be avoided in pure dermal CTNP, where surgical excision alone is acceptable in order to achieve optimal cosmetic results.