Joubert syndrome is a disorder that affects many parts of the body. The signs and symptoms of this condition vary among affected individuals, even among members of the same family.

The hallmark feature of Joubert syndrome is a combination of brain abnormalities that together are known as the molar tooth sign, which can be seen on brain imaging studies such as magnetic resonance imaging (MRI). This sign results from the abnormal development of structures near the back of the brain, including the cerebellar vermis and the brainstem. The molar tooth sign got its name because the characteristic brain abnormalities resemble the cross-section of a molar tooth when seen on an MRI.

Most infants with Joubert syndrome have low muscle tone (hypotonia) in infancy, which contributes to difficulty coordinating movements (ataxia) in early childhood. Other characteristic features of the condition include episodes of unusually fast (hyperpnea) or slow (apnea) breathing in infancy, and abnormal eye movements (ocular motor apraxia). Most affected individuals have delayed development and intellectual disability, which can range from mild to severe. Distinctive facial features can also occur in Joubert syndrome; these include a broad forehead, arched eyebrows, droopy eyelids (ptosis), widely spaced eyes (hypertelorism), low-set ears, and a triangle-shaped mouth.

Joubert syndrome can include a broad range of additional signs and symptoms. The condition is sometimes associated with other eye abnormalities (such as retinal dystrophy, which can cause vision loss, and coloboma, which is a gap or split in a structure of the eye), kidney disease (including polycystic kidney disease and nephronophthisis), liver disease, skeletal abnormalities (such as the presence of extra fingers and toes), or hormone (endocrine) problems. A combination of the characteristic features of Joubert syndrome and one or more of these additional signs and symptoms once characterized several separate disorders. Together, those disorders were referred to as Joubert syndrome and related disorders (JSRD). Now, however, any instances that involve the molar tooth sign, including those with these additional signs and symptoms, are usually considered Joubert syndrome.

What is Joubert syndrome?

Joubert syndrome is a rare brain malformation characterized by the absence or underdevelopment of the cerebellar vermis - an area of the brain that controls balance and coordination -- as well as a malformed brain stem (molar tooth sign). The most common features of Joubert syndrome in infants include abnormally rapid breathing (hyperpnea), decreased muscle tone (hypotonia), abnormal eye movements, impaired intellectual development, and the inability to coordinate voluntary muscle movements (ataxia). Physical deformities may be present, such as extra fingers and toes (polydactyly), cleft lip or palate, and tongue abnormalities. Kidney and liver abnormalities can develop, and seizures may also occur. Many cases of Joubert syndrome appear to be sporadic (not inherited). In most other cases, Joubert syndrome is inherited in an autosomal recessive manner (meaning both parents must have a copy of the mutation) via mutation in at least 10 different genes, including NPHP1, AHI1, and CEP290.

Is there any treatment?

Treatment for Joubert syndrome is symptomatic and supportive. Infant stimulation and physical, occupational, and speech therapy may benefit some children. Infants with abnormal breathing patterns should be monitored. Screening for progressive eye, liver, and kidney complications associated with Joubert-related disorders should be performed on a regular basis.

What is the prognosis?

The prognosis for infants with Joubert syndrome depends on whether or not the cerebellar vermis is partially developed or entirely absent, as well as on the extent and severity of other organ involvement, such as the kidneys and liver. Some children have a mild form of the disorder, with minimal motor disability and good mental development, while others may have severe motor disability, moderate impaired mental development, and multi-organ impairments.

• 25% chance to be affected
• 50% chance to be an unaffected carrier like each parent
• 25% chance to be unaffected and not a carrier.

• Each male child has a 50% chance to be unaffected, and a 50% chance to be affected
• Each daughter has a 50% chance to be unaffected, and a 50% chance to be an unaffected carrier

• thoroughly evaluating the family history
• addressing questions and concerns
• assessing recurrence risks
• facilitating genetic testing if desired
• discussing reproductive options

• the molar tooth sign on MRI
• hypotonia (weak muscle tone) in infancy with later development of ataxia
• developmental delays / intellectual disability