GRIN2A. “Certainty” is a word that can only be used so often in epilepsy genetics—and GRIN2A has demonstrated a somewhat puzzling tension between “certainty” and “uncertainty”. For example, the association between GRIN2A and focal/multifocal epilepsy with/without centrotemporal spikes, as well as risk for ESES, is well understood at this time. Likewise, the relationship between speech disorders—a unique feature in neurodevelopmental disorders—and GRIN2A has been established. However, as our knowledge of GRIN2A has expanded, our understanding of phenotype as it relates to severity has continued to grow uncertain. Even within the same family, GRIN2A may have a wide phenotypic range. And so, one of the mysteries of GRIN2A reveals itself: how can a gene that has such specificity in some of its phenotypic aspects simultaneously have such wide variability?