In Case 3, whole exome sequencing data were interrogated for candidate genes causing parkinsonism dystonia, thereby revealing a homozygous change (c.941C>T; Ala314Val) in SLC6A3. Retrospective single nucleotide polymorphism (SNP) array analysis confirmed that this SLC6A3 variant was contained within a 1.4 Mb region of homozygosity shared by the three affected siblings (Cases 1–3), with a different haplotype combination evident in both parents and the unaffected sisters (Fig. 1). The gene discussed is SLC6A3; the disease is Parkinson disease.