General Information

Mutations in ARID1A are rare and usually occur de novo. There is evidence that mutations in CSS are most often mosaic. In principle autosomal dominant inheritance is possible. However, patients with an ARID1A mutation have not been known to reproduce.

The most common clinical features of individuals with an ARID1A mutation, which do not have to be present in all, are developmental delay, intellectual disability, feeding difficulties, coarse facial features, speech delay, small or absent fifth finger or toe nail(s) and hypertrichosis. These features overlap with the phenotype of Coffin Siris Syndrome patients. In ARID1A patients we often see involvement of other nails as well, which is more pronounced than in other CSS patients.