Joubert syndrome is an autosomal recessive disorder presenting with psychomotor delay, hypotonia, ataxia, oculomotor apraxia, and neonatal breathing abnormalities. Neuroradiologically, Joubert syndrome is characterized by a peculiar malformation of the midbrain-hindbrain junction known as the 'molar tooth sign' (MTS) consisting of cerebellar vermis hypoplasia or aplasia, thick and maloriented superior cerebellar peduncles, and abnormally deep interpeduncular fossa.
The JBTS5 phenotype is mainly characterized by the neurologic and neuroradiologic features of Joubert syndrome associated with severe retinal and renal involvement. In addition, JBTS5 presents a broad clinical spectrum including incomplete phenotypes such as cerebelloretinal and cerebellorenal syndromes. The full-blown JBTS5 phenotype largely overlaps that of Senior-Loken syndrome (SLSN), which is characterized by retinitis pigmentosa plus juvenile nephronophthisis and is attributable to mutations in genes associated with nephronophthisis and encoding ciliary proteins. JBTS5 results from mutation of the CEP290 gene.
