Birt-Hogg-Dube (BHD) syndrome is a rare autosomal dominant genodermatosis characterized by skin tumors, including multiple fibrofolliculomas, trichodiscomas, and acrochordons. [ 1 ] These patients tend to develop renal and colonic carcinomas. [ 2 ] The defective gene in BHD syndrome has been identified and is suspected of being a tumor suppressor gene. Several mutations of the BHD gene have been reported. [ 3 ] All skin lesions in the syndrome may actually represent fibrofolliculomas cut in various planes of section.
A lentigo ( / l ɛ n ˈ t aɪ ɡ oʊ / ) (plural lentigines , / l ɛ n ˈ t ɪ dʒ ɪ n iː z / ) is a small pigmented spot on the skin with a clearly defined edge, surrounded by normal-appearing skin. It is a harmless (benign) hyperplasia of melanocytes which is linear in its spread. This means the hyperplasia of melanocytes is restricted to the cell layer directly above the basement membrane of the epidermis where melanocytes normally reside. This is in contrast to the "nests" of multi-layer melanocytes found in moles (melanocytic nevi ). Because of this characteristic feature, the adjective "lentiginous" is used to describe other skin lesions that similarly proliferate linearly within the basal cell layer.