XL-ID with or without nystagmus (rapid, involuntary eye movements) is a milder form of CASK-related intellectual disability. The intellectual disability in this form of the disorder can range from mild to severe; some affected females have normal intelligence. About half of affected individuals have nystagmus. Seizures and rhythmic shaking (tremors) may also occur in this form. The disease is Experimental Factor Ontology entry EFO_0010954 (cask-related x-linked intellectual disability). Also known as: XL-ID, x-linked cask-related intellectual disability.