Deletion 22q11 Syndrome Health Article

Definition

Deletion 22q11 syndrome is a relatively common genetic disorder characterized by congenital heart defects, palate abnormalities, distinct facial features, immune problems, learning disabilities and other abnormalities. This syndrome is caused by a deletion of chromosomal material from the long arm of chromosome 22 (22q) that leads to a wide spectrum of effects.

Description

Deletion 22q11 syndrome is also known as velocardiofacial syndrome, DiGeorge syndrome, Sphrintzen syndrome, conotruncal anomaly face syndrome, and the CATCH-22 syndrome. Because of the wide variability in the features of this syndrome, medical professionals originally thought that deletion 22q11 syndrome was more than one syndrome and it was separately described by a number of physicians—Dr. DiGeorge, Dr. Sphrintzen, and others. Dr. DiGeorge described the more severe end of deletion 22q11 syndrome (infants with congenital heart defects, unusual facial features and immune system abnormalities). The term velocardiofacial (VCF) syndrome was used for the milder end of deletion 22q11 syndrome. These individuals usually had palate anomalies, distinct facial features, and learning disabilities.

Deletion 22q11 syndrome is an extremely variable syndrome. The main features are congenital heart defects, distinctive facial features and palate (roof of the mouth) problems. Other problems include immune system abnormalities, thyroid problems, kidney abnormalities and learning difficulties including mild developmental delay. Very rarely do individuals have all of the problems associated with this syndrome. Most individuals with deletion 22q11 syndrome have only a few of the associated features. Some individuals with 22q11 deletion syndrome are very mildly affected and others are more severely affected. The reason for the wide variability in this syndrome is not known.

Genetic profile

Deletion 22q11 syndrome is a genetic disorder caused by a deletion of chromosomal material from the long arm of chromosome 22. A series of genes are located in this region. Individuals with deletion 22q11 syndrome may have some or all of these genes deleted. This syndrome is sometimes called a microdeletion syndrome or a contiguous gene syndrome. Contiguous refers to the fact that these genes are arranged next to each other. The size of the deletion can be large or small, which may explain why some individuals with deletion 22q11 syndrome are more severely affected than others. The exact genes responsible for this syndrome are not known.

Deletion 22q11 syndrome is an autosomal dominant disorder. Genes always come in pairs and in an autosomal dominant disorder only one gene needs too be missing or altered for an individual to have the disorder. About 10–15% of the time, deletion of the long arm of chromosome 22 that causes this syndrome is inherited from a parent. If a parent has deletion 22q11 syndrome, then there is a 50% chance they will pass the deletion on to each of their children who will also be affected with 22q11 syndrome. For reasons that are not understood, it is possible for a parent with mild features of deletion 22q11 syndrome to have a child with severe features of the syndrome.

Although deletion 22q11 syndrome is an autosomal dominant disorder, over 85–90% of individuals with this disorder are the only individuals in their family with this disorder. When this is the case, the chromosome deletion that causes deletion 22q11 syndrome is called de novo. A de novo deletion is one that occurs for the first time in the affected individual. The causes of de novo chromosome deletions are not known. Parents of a child with deletion 22q11 syndrome due to a de novo deletion are very unlikely to have a second child with deletion 22q11 syndrome.