ZC4H2 and Cognitive impairment: Intellectual disability was universally present in individuals with variants in ZC4H2 (5/5), DYNC1H1 (4/4), TOR1A (2/2), KAT6B (1/1), GLDN (1/1), and GPC3 (1/1), signifying a strong association between these genes and cognitive deficits.