A rare, genetic, syndromic intellectual disability characterized by global developmental delay, early-onset seizures, cerebellar atrophy, osteopenia, nystagmus and dysmorphic facial features, including bitemporal narrowing, prominent forehead, anteverted nares. Dysarthria, dysmetria, ataxic gait, spasticity and dysmorphic features have also been associated. The disease is Monarch Disease Ontology entry MONDO_0060627 (glycosylphosphatidylinositol biosynthesis defect 15).