From GeneReviews Overview
Classic Joubert syndrome (JS) is characterized by three primary findings: A distinctive cerebellar and brain stem malformation called the molar tooth sign (MTS). Hypotonia. Developmental delays. Often these findings are accompanied by episodic tachypnea or apnea and/or atypical eye movements. In general, the breathing abnormalities improve with age, truncal ataxia develops over time, and acquisition of gross motor milestones is delayed. Cognitive abilities are variable, ranging from severe intellectual disability to normal. Additional findings can include retinal dystrophy, renal disease, ocular colobomas, occipital encephalocele, hepatic fibrosis, polydactyly, oral hamartomas, and endocrine abnormalities. Both intra- and interfamilial variation are seen.
From OMIMJoubert syndrome-25 is an autosomal recessive ciliopathy characterized by delayed psychomotor development and oculomotor apraxia associated with cerebellar hypoplasia manifest as the molar tooth sign on brain imaging. The clinical manifestations appear to be confined to the neurologic system, as patients tend not to have additional renal, liver, or limb involvement (summary by Srour et al., 2015)
For a phenotypic description and a discussion of genetic heterogeneity of Joubert syndrome, see 213300.
http://www.omim.org/entry/616781