Joubert syndrome

Joubert syndrome is a rare genetic disorder that affects the area of the brain that controls balance and coordination.

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Presentation

The disorder is characterized by absence or underdevelopment of a part of the brain called the cerebellar vermis and a malformed brain stem (molar tooth sign). The most common features include ataxia (lack of muscle control), an abnormal breathing pattern called hypernea, sleep apnea, abnormal eye and tongue movements, and hypotonia. Other malformations such as extra fingers and toes, cleft lip or palate, tongue abnormalities, and seizures may also occur. There may be mild or moderate retardation. The syndrome was first identied by pioneering pediatric neurologist Dr. Marie Joubert in Montreal Canada, while working at the McGill Neurological Institute.

Treatment

Treatment for Joubert syndrome is symptomatic and supportive. Infant stimulation and physical, occupational, and speech therapy may benefit some patients. Infants with abnormal breathing patterns should be monitored.

Prognosis

The prognosis for individuals with Joubert syndrome varies. Some patients have a mild form with minimal motor disability and good mental development, while others may have severe motor disability and moderate mental retardation.

Genetics

Multiple genes that are mutated in individuals with Joubert syndrome have been identified:

• Mutations in a gene of unknown function called AHI1 is associated with a subset of Joubert syndrome cases. ^[1][2]

• In some rare cases of Joubert syndrome, mutations have been found in NPHP1 which is also associated with nephronophthisis, a cystic kidney disorder. ^[3]

• The gene CEP290 has been associated with both Joubert syndrome and Leber's congenital amaurosis, type 10.^[4]

References

1. ^ Ferland R. J. et al. Abnormal cerebellar development and axonal decussation due to mutations in AHI1 in Joubert syndrome. Nature Genetics, September 2004, 36:1008-1013.
2. ^ Dixon-Salazar T. et al. Mutations in the AHI1 gene, encoding jouberin, cause Joubert syndrome with cortical polymicrogyria. "American Journal of Human Genetics", December 2004, 75(6):979-87.
3. ^ Parisi M. A. et al. The NPHP1 gene deletion associated with juvenile nephronophthisis is present in a subset of individuals with Joubert syndrome. American Journal of Human Genetics, July 2004, 75:82-91.
4. ^ Traboulsi EI, Koenekoop R, Stone EM (2006). "Lumpers or splitters? The role of molecular diagnosis in Leber congenital amaurosis". Ophthalmic Genet. 27 (4): 113–5. doi:10.1080/13816810601013146. PMID 17148037.