TBP and cerebellar ataxia: To identify the genetic cause underlying the progressive chorea and dystonia phenotype within this family, and because proband III:8 tested negative for mutations in known genes present in an in‐house gene panel (design 2017, Table S1) and was negative for repeat expansions in the HTT, HDL genes JPH3 (HDL‐2) and TBP [HDL‐4/spinocerebellar ataxia (SCA17)], and benign hereditary chorea (NKX2‐1) (Table S2), WES was performed in affected individuals III:8 and IV:5 and unaffected family member III:14.