RAD51C and spinocerebellar ataxia, autosomal recessive, with axonal neuropathy: In SCAN-B Cluster s4, these features of HR deficiency were the result of a composition of alterations in HR-associated driver genes, including germline (19%) and somatic (14%) mutations in BRCA2, promoter hypermethylation of RAD51C (29%), and germline PALB2 mutation (19%).