Joubert Syndrome (JBTS)
In a nutshell
Joubert Syndrome is a rare developmental disorder affecting mainly the brain, particularly the cerebellum, which may be accompanied by renal and/or retinal symptoms. It leads to low muscle tone at birth and developmental delay, and there may be breathing abnormalities and movement disorders. Brain scans show a characteristic feature named the “molar tooth sign”. It is caused by mutations in several genes associated with cilia, often inherited in an autosomal recessive manner. No cure is currently available, only supportive therapy.
Joubert Syndrome is a rare developmental disorder affecting mainly the brain but this might be accompanied by renal and/or retinal symptoms. Mutations in several genes associated with cilia can cause Joubert Syndrome which are inherited often in a autosomal-recessive manner but x-chromosomal-recessive inheritance also occurs.
Primary features
- Abnormalities of the brain, mainly the cerebellum-part lead to low muscle tone at birth, developmental delay and there may also be breathing abnormalities and movement disorders.
- Brain scans such as magnetic resonance tomography (MRI) show a characteristic feature of the disease, named the “molar tooth sign”.
- Renal disease, usually in the form of Nephronophthisis, may also occur and can lead to renal insufficiency.
- Babies can be observed to have poor sight at birth which can improve when the body learns to co-ordinate movement and muscle tone develops. Mystagmus is common.
- Extra fingers and toes (Polydactyly) are sometimes observed.
Impact
- There is a broad phenotypic spectrum of the brain phenotype among patients ranging from developmental delay and slight movement problems to severe brain defects including open brain that might be incompatible with life.
- Breathing problems are due to cerebral mis-regulation rather than to primary problems in the respiratory tract. Newborn babies sometimes require a tracheostomy to help with breathing difficulties.
- No cure is currently available for Joubert Syndrome, only supportive therapy.
Find out more
Last reviewed: August 2026