Joubert syndrome

Alternative Names:  Cerebellar vermis agenesis or Cerebelloparenchymal disorder IV

Definition:
Joubert syndrome is a rare inherited disorder of the brain. It is a genetic birth defect in which the area of the brain that controls balance and coordination is underdeveloped.It 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. The most common features of Joubert syndrome in infants include abnormally rapid breathing (hyperpnea), decreased muscle tone (hypotonia), jerky eye movements (oculomotor apraxia), mental retardation, and the inability to coordinate voluntary muscle movements (ataxia).

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An area at the back of the brain which is important for balance and co-ordination, called the cerebellum normally has two interconnected halves or hemispheres. In Joubert syndrome the connection between the two halves, known as the cerebellar vermis, fails to develop properly. As a result, one of the main features of Joubert syndrome is poorly controlled or unsteady movement, known as ataxia.

The severity of the condition varies from child to child, depending on the extent of the abnormalities of the brain. Some children are only mildly affected while others (even within the same family) have severe disabilities.

It occurs in both males and females, in about one in 100,000 births. Joubert syndrome often occurs in a child with no family history of the disorder, but in some children the syndrome appears to be inherited.

Symptoms:
The symptoms of Joubert syndrome are related to the underdevelopment of an area of the brain called the cerebellar vermis, which controls balance and muscle coordination. The symptoms, which may range from mild to severe depending on how much the brain is underdeveloped, may include:

•Periods of abnormally rapid breathing (episodic hyperpnea), which may seem like panting

•jerky eye movements (nystagmus)

•characteristic facial features such as drooping eyelids (ptosis), open mouth with protruding tongue, low-set ears

•mental retardation

•difficulty coordinating voluntary muscle movements (ataxia)
Other birth defects such as extra fingers and toes (polydactyly), heart defects, or cleft lip or palate may be present. Seizures may also occur.

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Causes:
Joubert syndrome is a genetic abnormality inherited in an autosomal recessive fashion. This means that if both parents are carriers, there is a 1 in 4 chance that each child will have the disease.

Diagnosis:
The most pronounced symptom in a newborn infant with Joubert syndrome is periods of abnormally rapid breathing, which may be followed by stopping breathing (apnea) for up to one minute. Although these symptoms may occur in other disorders, there are no lung problems in Joubert syndrome, which helps identify it as the cause of the abnormal breathing.

A magnetic resonance imaging (MRI) scan can look for the brain abnormalities that are present in Joubert syndrome and confirm the diagnosis.

Treatment:
There is no cure for Joubert syndrome, so treatment focuses on the symptoms such as breathing problems and to support the child’s development.. Infants with abnormal breathing may have a breathing (apnea) monitor for use at home, especially at night. Physical, occupational, and speech therapy may be helpful for some individuals. Individuals with heart defects, cleft lip or palate, or seizures may require more medical care.

Prognosis:
The prognosis for infants with Joubert syndrome depends on whether or not the cerebellar vermis is partially developed or entirely absent. Some children have a mild form of the disorder, with minimal motor disability and good mental development, while others may have severe motor disability and moderate mental retardation.

Research:
The NINDS supports research on the development of the nervous system and the cerebellum. This research is critical for increasing our understanding of Joubert syndrome, and for developing methods of treatment and prevention. NINDS, in conjunction with the NIH Office of Rare Disorders, sponsored a symposium on Joubert syndrome in 2002. Research priorities for the disorder were outlined at this meeting.

Research has revealed that a number of genetic disorders, not previously thought to be related, may indeed be related as to their root cause. Joubert syndrome is one such disease. It is a member of an emerging class of diseases called cilopathies.

The underlying cause of the ciliopathies may be a dysfunctional molecular mechanism in the primary cilia structures of the cell, organelles which are present in many cellular types throughout the human body. The cilia defects adversely affect “numerous critical developmental signaling pathways” essential to cellular development and thus offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases.

Currently recognized ciliopathies include Joubert syndrome, primary ciliary dyskinesia, Bardet-Biedl syndrome, polycystic kidney disease and polycystic liver disease, nephronophthisis, Alstrom syndrome, Meckel-Gruber syndrome and some forms of retinal degeneration.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose

Resources:
http://www.bbc.co.uk/health/physical_health/conditions/joubert1.shtml
http://www.ninds.nih.gov/disorders/joubert/joubert.htm
http://www.ninds.nih.gov/disorders/joubert/joubert.htmhttp://www.ninds.nih.gov/disorders/joubert/joubert.htm

http://www.joubertfoundation.com/

http://www.health-news-blog.com/blogs/permalinks/6-2007/the-fifth-gene-responsible-for-joubert-syndrome.html

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