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Clinical features
All patients with ARID1B mutations identified so far have a degree of intellectual disability, ranging from mild to severe. Speech delay and feeding difficulties are often reported. Other features, which are not present in all patients, include hypertrichosis, hypoplastic nails, short fifth rays of hands and feet. See also under clinical features (Santen, Clayton-Smith, & consortium, 2014).

ARID1B is the most frequently mutated gene in Coffin-Siris Syndrome and one of the most frequently mutated genes in intellectual disability.

Genetic counselling
Mutations in ARID1B are inherited in an autosomal dominant manner, but to date almost all cases result from a de novo mutation. Thus, the affected individuals represent sporadic cases, i.e., a single occurrence in a family. The recurrence risk for future pregnancies is considered low (probably <1%). One individuals with ARID1B-related intellectual disability have been known to reproduce (Smith, Holden, Friez, Jones, & Lyons, 2016). Prenatal testing is technically feasible, but the likelihood of recurrence in families who have had an affected child is considered low based upon the current knowledge.