TDP1 and cerebellar ataxia: Mutations in APTX and TDP1 have been reported to cause both ataxia with oculomotor apraxia type 1 (AOA1, for APTX) [23] and spinocerebellar ataxia with axonal neuropathy type 1 (SCAN1, for TDP1) [24] with both presenting with ataxia, a feature often, although not exclusively, associated with mitochondrial disease [25].