Autosomal dominant non-syndromic intellectual disability

Autosomal dominant non-syndromic intellectual disability (also referred to as autosomal dominant mental retardation or ADID) is a group of genetically heterogeneous conditions characterized by significant limitations in intellectual functioning and adaptive behavior that arise during the developmental period, without the additional systemic features or recognizable physical patterns that define syndromic forms of intellectual disability. The condition is caused by heterozygous pathogenic variants in any of numerous genes, with many distinct genetic subtypes identified (designated MRD1 through MRD70+ in OMIM). These genes are involved in critical neurodevelopmental pathways including synaptic signaling, chromatin remodeling, and transcriptional regulation, primarily affecting the central nervous system. The core clinical feature is intellectual disability ranging from mild (ICD-10: F70) to profound (ICD-10: F73), manifesting as delays in cognitive development, speech and language acquisition, learning, and adaptive skills such as social functioning and daily living activities. By definition, the condition is non-syndromic, meaning that affected individuals do not have a consistent pattern of major congenital malformations, distinctive facial features, or multi-organ involvement, although minor or variable associated features such as behavioral difficulties, attention problems, or mild motor delays may sometimes be present. Onset is typically recognized in infancy or early childhood when developmental milestones are not met at expected ages. There is currently no cure or disease-specific pharmacological treatment for autosomal dominant non-syndromic intellectual disability. Management is supportive and multidisciplinary, focusing on early intervention programs, speech and language therapy, occupational therapy, special education services, and behavioral support. Genetic counseling is important for affected families, as the condition follows an autosomal dominant inheritance pattern, meaning each child of an affected individual has a 50% chance of inheriting the causative variant. However, many cases arise from de novo (new) mutations, with no prior family history of the condition.

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