Joubert syndrome type 9

Joubert syndrome type 9

An autosomal recessive disorder (OMIM:612285) presenting with cerebellar ataxia, oculomotor apraxia, hypotonia, neonatal breathing abnormalities and psychomotor delay, variably accompanied by retinal dystrophy and renal disease.

Neuroimaging
Cerebellar vermis hypoplasia/aplasia, thickened or reoriented superior cerebellar peduncles and markedly enlarged interpeduncular fossa, giving the appearance of a molar tooth on transaxial slices (molar tooth sign).

Molecular pathology
Defects of CC2D2A, which encodes a protein required for ciliogenesis and sonic hedgehog/SHH signalling, cause Joubert syndrome type 9.