Orofaciodigital Syndrome Type 6

Joubert syndrome with orofaciodigital defect (or oral-facial-digital syndrome type 6, OFD6) is a very rare subtype of Joubert syndrome and related disorders (JSRD, see this term) characterized by the neurological features of JS associated with orofacial anomalies and often polydactyly.

Epidemiology

Prevalence is unknown.

Clinical description

Typical oral findings include bifid or lobulated tongue, lingual hamartomas and multiple oral frenulae, but cleft lip and/or palate can also be present. Polydactyly is typically mesaxial with Y-shaped metacarpals, but can also be preaxial or postaxial. A subset of patients present with hypothalamic hamartoma that has never been reported in other JSRD subgroups.

Etiology

Two OFD6 patients, including one fetus, were found to carry a homozygous mutation in the TMEM216 gene (11q13.1), but mutations in this gene were excluded in several other patients, and the genetic basis of this condition still remains elusive.

Genetic counseling

Males and females are equally affected and an autosomal recessive pattern of inheritance was observed in familial cases.