X-linked infantile spasm syndrome - Genetics Home Reference
X-linked infantile spasm syndrome
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Reviewed August 2012
What is X-linked infantile spasm syndrome?
X-linked infantile spasm syndrome is a seizure disorder characterized by a type of seizure known as infantile spasms. The spasms usually appear before the age of 1. Several types of spasms have been described, but the most commonly reported involves bending at the waist and neck with extension of the arms and legs (sometimes called a jackknife spasm). Each spasm lasts only seconds, but they occur in clusters several minutes long. Although individuals are not usually affected while they are sleeping, the spasms commonly occur just after awakening. Infantile spasms usually disappear by age 5, but many children then develop other types of seizures that recur throughout their lives.
Most babies with X-linked infantile spasm syndrome have characteristic results on an electroencephalogram (EEG), a test used to measure the electrical activity of the brain. The EEG of these individuals typically shows an irregular pattern known as hypsarrhythmia, and this finding can help differentiate infantile spasms from other types of seizures.
Because of the recurrent seizures, babies with X-linked infantile spasm syndrome stop developing normally and begin to lose skills they have acquired (developmental regression), such as sitting, rolling over, and babbling. Subsequently, development in affected children is delayed. Most affected individuals also have intellectual disability throughout their lives.
Most babies with X-linked infantile spasm syndrome have characteristic results on an electroencephalogram (EEG), a test used to measure the electrical activity of the brain. The EEG of these individuals typically shows an irregular pattern known as hypsarrhythmia, and this finding can help differentiate infantile spasms from other types of seizures.
Because of the recurrent seizures, babies with X-linked infantile spasm syndrome stop developing normally and begin to lose skills they have acquired (developmental regression), such as sitting, rolling over, and babbling. Subsequently, development in affected children is delayed. Most affected individuals also have intellectual disability throughout their lives.
How common is X-linked infantile spasm syndrome?
Infantile spasms are estimated to affect 1 to 1.6 in 100,000 individuals. This estimate includes X-linked infantile spasm syndrome as well as infantile spasms that have other causes.
What genes are related to X-linked infantile spasm syndrome?
X-linked infantile spasm syndrome is caused by mutations in either the ARX gene or the CDKL5 gene. The proteins produced from these genes play a role in the normal functioning of the brain. The ARX protein is involved in the regulation of other genes that contribute to brain development. The CDKL5 protein is thought to regulate the activity of at least one protein that is critical for normal brain function. Researchers are working to determine how mutations in either of these genes lead to seizures and intellectual disability.
Infantile spasms can have non-genetic causes, such as brain malformations, other disorders that affect brain function, or brain damage. In addition, changes in genes that are not located on the X chromosome cause infantile spasms in rare cases.
Read more about the ARX and CDKL5 genes.
Infantile spasms can have non-genetic causes, such as brain malformations, other disorders that affect brain function, or brain damage. In addition, changes in genes that are not located on the X chromosome cause infantile spasms in rare cases.
Read more about the ARX and CDKL5 genes.
New on the MedlinePlus Epilepsy page:
09/10/2012 08:00 PM EDT
Source: National Library of Medicine - 
09/06/2012 08:00 PM EDT
Source: National Institute of Environmental Health Sciences -
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