For the two mutational signatures, 1 and 5, proposed to be associated with age at diagnosis [42], a significant linear trend of increasing signature proportions with age at diagnosis was observed across all SCAN-B cases (linear regression p = 0.007 for signature 1 and p = 2e−6 for signature 5, Additional file 4A). Here, PPIB is linked to spinocerebellar ataxia, autosomal recessive, with axonal neuropathy.