A mutation in the ARID1B gene can cause Coffin Siris Syndrome, but can also lead to developmental delay and intellectual disability without the typical Coffin-Siris Syndrome related features.

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 et al., 2014).

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