We found that individuals with PTV/dels in STXBP1 were nominally associated with West syndrome (OR 1.60, 95% CI 0.95–2.73) and phenotypic features including ‘Infantile spasms’ (HP:0012469, OR 1.59, 95% CI 1.08–2.35) and ‘Ataxia’ (HP:0001251, OR 1.84, 95% CI 1.20–2.84), while individuals with missense variants were more likely to have other DEE (OR 2.05, 95% CI 1.28–3.32; Supplementary Table 9). Here, STXBP1 is linked to cerebellar ataxia.