STXBP1 and infantile spasms: By assessing the true frequency of clinical features within subgroups (e.g. variant types) and across all individuals with STXBP1-related disorders, clinicians can better counsel patients on the relative risk of developing certain clinical features, such as the increased risk of infantile spasms in individuals with PTV/del in STXBP1, as well as reference an expected time frame for developmental milestones and allow for early intervention.