Kleefstra syndrome

Kleefstra syndrome, also known as 9q34 deletion syndrome, is a rare genetic disorder. Terminal deletions of chromosome 9q34 are associated with childhood hypotonia, a distinctive facial appearance and intellectual disability, usually in the moderate to severe range though a minority have mild delays. Typical facial features include arched eyebrows, microcephaly, midface hypoplasia, a prominent jaw and a pouting lower lip. Speech is often markedly delayed, with severe expressive language delay although general language development is often more advanced. Other common features include epilepsy, congenital and urogenital anomalies, obesity and psychiatric disorders. Kleefstra and colleagues identified EHMT1, which encodes a histone methyltransferase, as the causative gene.