This is a subtype of Lynch Syndrome characterised by the presence of skin tumours including sebacious gland tumours (sebaceous adenoma, sebaceous epithelioma, or sebaceous carcinoma) and keratoacanthomas, first identified in the late 1960s. In one study Muir-Torre was observed to occur in 14 of 50 families (28%) and in 14 of 152 individuals (9.2%) with Lynch Syndrome (South, Hampel et al 2008). The skin tumours in this condition tend to have the same molecular changes that are associated with Lynch Syndrome such as microsatellite instability and loss of expression of proteins associated with DNA mismatch repair deficiency.
This condition is usually managed by annual review with a dermatologist. There is some evidence for the use of isotretinoin – dosage of as much as 0.8 mg/kg/d may be effective. Graefe et alnote in a case report that the combination of interferon with retinoids may be of promise to prevent cutaneous tumor development in persons with MTS. They used interferon (interferon alfa-2a) SC 3 X 106 U 3 times/wk in combination with 50 mg isotretinoin daily and topical isotretinoin gel. Patients should also have treatment as per Lynch Syndrome described in this section including regular colonoscopic surveillance, daily aspirin, etc. Mutations in MLH1 and MSH2 genes are more common than MSH6 or PMS2.