Joubert syndrome is a rare genetic disorder that affects the cerebellum, an area of the brain that controls balance and coordination.
The disorder is characterized by absence or underdevelopment of the cerebellar vermis and a malformed brain stem (molar tooth sign). The most common features include ataxia (lack of muscle control), hyperpnea (abnormal breathing patterns), 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. Joubert syndrome is one of the many genetic syndromes associated with syndromic retinitis pigmentosa. The syndrome was first identified by pioneering pediatric neurologist Marie Joubert in Montreal, Canada, while working at the Montreal Neurological Institute and McGill University.
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.
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.
Multiple genes that are mutated in individuals with Joubert syndrome have been identified:
- JBTS3: Mutations in a gene of unknown function called AHI1 is associated with a subset of Joubert syndrome cases.
- JBTS4: In some rare cases of Joubert syndrome, mutations have been found in NPHP1 which is also associated with nephronophthisis, a cystic kidney disorder.
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