Genetic predisposition – understanding underlying mechanisms of onychomycosis

[[[ Background: ]]] There are numerous factors that predispose to onychomycosis including genetic predisposition, diabetes mellitus, immunosuppression, vascular disease and psoriasis. [[[ Objectives: ]]] The aims of this workshop were to discuss current knowledge of genetic risk factors and the approaches that should be used to investigate underlying mechanisms. [[[ Results: ]]] The high prevalence of onychomycosis within certain families was initially attributed to intrafamilial transmission. However, the low prevalence of infection in people marrying into infected families together with the high prevalence among their offspring suggested a genetic basis. The state-of-the-art pedigree study by Zaias et al. suggested that Trichophyton rubrum infection shows an autosomal dominant pattern of inheritance. A consensus was reached that epidemiological and genetic studies are required to investigate this issue further. For epidemiological studies, families in which two or three generations are infected with T. rubrum should be selected. Patients with T. rubrum on different body sites should be included, and the presence of associated diseases or other common features in these individuals should be investigated to identify trigger factors. [[[ Conclusion: ]]] Genetic studies should explore the mode of inheritance of onychomycosis and look for the disease gene(s). Serum samples from patients and age-sex matched controls must be analysed centrally. The results of these studies will make it possible to develop therapeutic, preventive and prophylatic measures and to provide patients and their families with information.