Our study reviews the prevalence of undiagnosed tumour predisposition disorders, schwannomatosis and NF2, in apparent cases of sporadic vestibular schwannoma (VS). We found that undiagnosed predisposition to these tumours may account for a significant proportion of apparently sporadic VS cases, especially in those presenting at a lower age. Somatic mutations in NF2 were common throughout VS tumours, regardless of germline mutation status. Identification of germline pathogenic variants that predispose to multiple tumours, and the somatic variant patterns, is important for development of genetic testing protocols and leads to improved genetic counselling and clinical management. (By Katie Sadler, https://jmg.bmj.com/content/early/2020/06/23/jmedgenet-2020-107022 )