Joubert syndrome

Joubert syndrome is a condition that affects the development of the brain. This condition can also impact many other parts of the body. The signs and symptoms seen in people with Joubert syndrome can vary, even among members of the same family.

The hallmark feature of Joubert syndrome is a combination of brain abnormalities called the molar tooth sign, which can be seen using magnetic resonance imaging (MRI). The molar tooth sign occurs when structures near the back of the brain, including the brainstem and the central part of the cerebellum (vermis), develop abnormally. This sign got its name because these brain abnormalities resemble the shape or outline of a molar tooth when seen on an MRI scan.

Infants with Joubert syndrome often have low muscle tone (hypotonia) and may experience breathing problems, with episodes of unusually fast (hyperpnea) or slow (apnea) breathing. Abnormal eye movements, which can include rapid, involuntary eye movements (nystagmus) or problems with side-to-side movements of the eyes (oculomotor apraxia), are also common.

Most individuals with Joubert syndrome have intellectual disabilities, which can range from mild to severe. Children with Joubert syndrome often have delayed development of speech and motor skills, such as sitting and walking. Problems with coordination and balance (ataxia) are common, but ataxia may become less severe over time. Most children with Joubert syndrome learn to walk on their own, although some affected individuals require walking support or wheelchair assistance.

Additional signs and symptoms that are seen in people with Joubert syndrome can include seizures, difficulty regulating body temperature, and behavioral problems. People with Joubert syndrome may have a broad range of other signs and symptoms. Kidney disease, liver disease, skeletal abnormalities (such as the presence of extra fingers and toes), or hormone (endocrine) problems may occur in affected individuals. Eye abnormalities may also be present and can include the breakdown of the light-sensitive tissue at the back of the eye (retinal dystrophy), which can cause vision loss.

In the past, individuals with the molar tooth sign were separated into different subgroups of Joubert syndrome based on their additional features. The term “Joubert syndrome and related disorders” (JSRD) was used to refer to these subgroups. Today, all people with the molar tooth sign, including those with additional signs and symptoms, are considered to have Joubert syndrome.