Muir-Torre syndrome.

Muir-Torre syndrome is an autosomal-dominant skin condition of genetic origin, characterised by tumours of the sebaceous gland or keratoacanthoma that are associated with visceral malignant diseases. The cutaneous characteristics of Muir-Torre syndrome are sebaceous adenoma, epithelioma, carcinoma, or multiple keratoacanthomas, whereas visceral malignant diseases include colorectal, endometrial, urological, and upper gastrointestinal tumours. Although Muir-Torre syndrome has a striking familial association and features of autosomal-dominant transmission, it can arise in individuals without a family history or any known mutations. Clinical and biomolecular evidence has suggested that there are two types of Muir-Torre syndrome. The most common is a variant of hereditary non-polyposis colorectal cancer, which is characterised by defects in mismatch repair genes and early-onset tumours. The second type does not show deficiency in mismatch repair and its pathogenesis remains undefined. Diagnosis of these rare sebaceous lesions warrants the search for associated internal malignant diseases: the peculiarity of skin lesions and their biomolecular characterisation with microsatellite instability analysis and immunohistochemistry could be used to identify familial Muir-Torre syndrome, allowing clinicians to tailor a personalised programme to screen for skin and visceral malignant diseases in high-risk individuals.