Joubert Syndrome

What is Joubert syndrome?

Joubert syndrome is a rare genetic disorder that affects the area of the brain that controls balance and coordination. Specifically, this condition is characterized by a particular MRI finding called a “motor tooth sign,” in which the cerebellar vermis of the brain is absent or underdeveloped with an abnormal brain stem.

What causes Joubert syndrome?

Joubert syndrome is inherited as an autosomal recessive genetic disorder. Ten genes have been identified to play a role in Joubert syndrome (most commonly, the AHI1, NPHP1, and CEP290 genes), and other genes are still currently unknown. However, all of these genes are known or suspected to play roles in cilia, which are microscopic, finger-like projections that stick out from the surface of cells and are involved in the body’s chemical signaling. Thus, it is speculated that disruptions to the normal functioning of these cilia probably disrupt important chemical signaling pathways during development, leading to the Joubert syndrome.

What are the symptoms of Joubert syndrome?

Most of the clinical symptoms of Joubert syndrome are apparent in infancy, as children have delays in gross motor milestones. The condition has a full spectrum of symptoms, but the most common features of Joubert syndrome are the following:

Lack of muscle control
Abnormal breathing patterns
Sleep apnea
Abnormal eye and tongue movements
Low muscle tone
Eye problems, such as abnormal development of the retina, coloboma, abnormal eye movements, crossed eyes, and drooping eyelids

Less frequent symptoms of Joubert syndrome include the following:

Kidney and/or liver abnormalities
Extra fingers and toes
Hormone abnormalities
Gap in the skull with protrusion of the brain membranes (encephalocele)

How is Joubert syndrome diagnosed?

Joubert syndrome is based on an observation of the physical symptoms of the condition and the “molar tooth sign” as seen on an MRI scan. In addition, molecular genetic testing is available for the four common genes associated with Joubert syndrome, and carrier and prenatal diagnostic testing is available if one of the gene mutations has been identified in a family member.

What are the available treatments for Joubert syndrome?

Unfortunately, there is no cure for Joubert syndrome as of yet, so treatment for the condition is symptomatic and supportive. In particular, the developmental delays associated with the condition are usually treated with physical therapy, occupational therapy, speech therapy, and infant stimulation. An affected individual should also be regularly screened for any liver, kidney, and/or retinal complications that may occur, so these can be treated promptly using traditional therapies.