To date, several disease-associated complex TRs have been reported, including 400–2000 copies of AAAAG, AAAGG, AAGAG, and AGAGC in RFC1, which are associated with cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS)25; the loss of CAA and CCA in (CAG)m CAA CAG CCA (CCG)n, the motif structure of HTT gene, are associated with Huntington’s disease (HD)26, CAG and ACT in ATXN8 are with spinocerebellar ataxia type 8 (SCA8)27, CAGG, CA, and CAGA in CNBP with myotonic dystrophy type 2 (DM2)28, and TTTCA and TTTTA in SAMD12 with benign adult familial myoclonic epilepsy (BAFME)29. Here, SAMD12 is linked to myotonic dystrophy type 2.