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Joubert's syndrome

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Synonyms: Joubert-Boltshauser syndrome, cerebelloparenchymal disorder IV, familial cerebellar vermis agenesis, cerebello-oculo-renal syndrome.1

Joubert's syndrome is a rare autosomal recessive condition characterised by partial or complete absence of the cerebellar vermis, leading to neonatal breathing abnormalities, jerky eye movements, hypotonia, ataxia, impaired equilibrium, and mental handicap.2

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The incidence of Joubert's syndrome has been estimated to range between 1/80,000 and 1/100,000 live births, although this may be an underestimate.3


Joubert's syndrome is transmitted as an autosomal recessive trait (genetic heterogeneity - chromosome 9 is a possible candidate4). Mutations in five genes have been identified, including AHI1, NPHP1 and RPGRIP1L.56

Recurrence risk is 25% in most families, although X-linked inheritance should also be considered.

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Onset is in early infancy with abnormally rapid breathing, jerky eye movements, mental retardation, hemifacial spasms, seizures and ataxia:

  • Eyes: abnormal eye movements, chorioretinal coloboma, ptosis, and retinal dysplasia.

  • Mouth: tongue tumours and protrusion.

  • Hand and foot: polydactyly.

  • Neurological: hypotonia, hypoplasia or aplasia of the cerebellar vermis, occasional occipital meningo-encephalocele, hemifacial spasms and ataxia.

  • Gastrointestinal: duodenal atresia or fibrosis.

  • Renal: cystic kidneys.

  • Mental and motor retardation.

  • Behavioural problems: self-mutilation.

  • Neonatal apnoea followed by episodic hyperpnoea which may improve and subsequently disappear.


  • The diagnosis of Joubert's syndrome is confirmed with MRI, which shows classic neuroradiological finding of a complex midbrain-hindbrain malformation known as the 'molar tooth sign' (MTS), originating from the association of cerebellar vermis hypoplasia, horizontally-oriented and thickened superior cerebellar peduncles and a deepened interpeduncular fossa ('molar tooth sign').27

  • Detection of the MTS should be followed by a diagnostic protocol to assess multi-organ involvement.

  • MRI findings also include dilated cisterna magna, occipital meningo-encephalocele, Dandy-Walker malformation, hypoplasia of the corpus callosum, retrobulbar cystic mass.

  • Abdominal ultrasound may show cystic kidneys.

  • Genetic testing is not currently available but the physical abnormalities may be detected at antenatal ultrasound. A fetal MRI scan at between 20 and 22 weeks of gestation has been shown to be an effective method of antenatal diagnosis.8

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Differential diagnosis

Other autosomal recessive ataxias, eg Friedreich's ataxia, ataxia-telangiectasia.9

Associated disorders

Leber's amaurosis (blindness with normal optic fundi and brain and kidney abnormalities) may be associated.


  • Treatment is symptomatic and supportive and will include physiotherapy, and occupational and speech therapy.

  • The parents will need a great deal of support.


  • This depends on the degree of malformation or agenesis of the cerebellar vermis.

  • Some will have a mild form with mild physical disability and good mental development.

  • In others, there may be severe physical disability, moderate mental retardation and death in infancy or early childhood.

Further reading and references

  • Parisi MA; Clinical and molecular features of Joubert syndrome and related disorders. Am J Med Genet C Semin Med Genet. 2009 Nov 15;151C(4):326-40.
  1. Joubert M, Eisenring JJ, Robb JP, et al; Familial agenesis of the cerebellar vermis. A syndrome of episodic hyperpnea, abnormal eye movements, ataxia, and retardation.; Neurology. 1969 Sep;19(9):813-25.
  2. Valente EM, Brancati F, Dallapiccola B; Genotypes and phenotypes of Joubert syndrome and related disorders. Eur J Med Genet. 2008 Jan-Feb;51(1):1-23. Epub 2007 Nov 23.
  3. Brancati F, Dallapiccola B, Valente EM; Joubert Syndrome and related disorders. Orphanet J Rare Dis. 2010 Jul 8;5:20.
  4. Joubert Syndrome, Online Mendelian Inheritance in Man (OMIM)
  5. Louie CM, Gleeson JG; Genetic basis of Joubert syndrome and related disorders of cerebellar development.; Hum Mol Genet. 2005 Oct 15;14 Spec No. 2:R235-42.
  6. Harris PC; Genetic complexity in Joubert syndrome and related disorders. Kidney Int. 2007 Dec;72(12):1421-3.
  7. Merritt L; Recognition of the clinical signs and symptoms of Joubert syndrome.; Adv Neonatal Care. 2003 Aug;3(4):178-86; quiz 187-8.
  8. Doherty D, Glass IA, Siebert JR, et al; Prenatal diagnosis in pregnancies at risk for Joubert syndrome by ultrasound and MRI.; Prenat Diagn. 2005 Jun;25(6):442-7.
  9. Espinos-Armero C, Gonzalez-Cabo P, Palau-Martinez F; [Autosomal recessive cerebellar ataxias. Their classification, genetic features and pathophysiology]; Rev Neurol. 2005 Oct 1-15;41(7):409-22.

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