Prior genetic testing for microarray CGH, fragile X single‐gene testing, and clinical exome analysis of panels for ataxia, dystonia and hyperkinesia were negative (N.B. STXBP1 was not included in these gene panels), and neurometabolic investigations on blood, urine, and CSF were non‐diagnostic (Supplementary Information). This evidence concerns the gene STXBP1 and cerebellar ataxia.