Williams Syndrome (WS) is a genetic disorder. It is caused by a deletion of genetic materials on chromosome 7. Research states that the cause of WS is mainly random and that parents without previous history of WS may have a child with WS. However, WS can be inherited too. Research indicates that a person with WS has a 50% chance of passing on this syndrome to his or her children.
Researchers are growing more interested in identifying the effects of genes deletion on chromosome 7. However, only 2 genes out of the hundreds of genes on chromosome 7 have been extensively studied: Elastin (ELN) and LIN Kinase 1 (LIMK1). ELN is a protein that permits blood vessels and other tissues in the body to stretch. The deletion of a copy of ELN results in the narrowing of blood vessels, stretchy skin, and flexible joints. LIMK1 is a gene that is involved in neuronal development. The deletion of a copy of LIMK1 is thought to be associated with abnormal brain function.
WS causes multiple developmental problems, including heart and narrowed blood vessels, musculoskeletal problems, and learning disabilities. This disorder occurs in approximately 1 in 10,000 people, according to the Williams Syndrome Association.
An image of the genes that are deleted in chromosome 7.
Detection & Diagnosis
Diagnosis of Williams Syndrome is determined through
lab testing.
Most mothers of children living with Williams Syndrome (WS) say their pregnancy was normal. However, babies with WS often have trouble feeding and sleeping, and they may seem colicky (excessive and inconsolable crying). They are also more likely to have hernias and constipation. In addition, babies with WS often begin walking and talking late. These symptoms may lead parents to bring their babies to the doctor.
Specialists can administer clinical tests that take into account facial features, developmental delay, calcium levels, and presence of hernias, heart disease, and heart defects. However, these clinical tests are not as effective as lab testing.
Lab testing provides a definite diagnosis by examining DNA. The most common lab test is the fluorescence in situ hybridization (FISH). The FISH test identifies abnormalities in chromosomes. The FISH test is very expensive, so researchers are investigating other types of less expensive lab tests, such as multiplex ligation-dependent probe amplification (MLPA). The MLPA is less expensive than the FISH, but it is not always available where people live.
REFERENCES
Edmunds, A. & Edmunds, G. (2014) Special Education in Canada, Oxford University Press, pg. 234-235.
Gordan, N. (2006) Review Article: Williams Syndrome. Journal of Pediatric Neurology 4(1), 11-14.
Gray, V., Karmiloff Smith, A., Funnell, E., & Tassabehji, M. In-depth analysis of spatial cognition in Williams syndrome: a critical assessment of the role of the LIMK1 gene. Neuropsychologia 44(5), 679-685.
Herndon, J. (2012). Williams Syndrome. Retrieved from http://www.healthline.com/health/williams-syndrome#Overview1
Pober, B. R. (2010). Williams–Beuren syndrome. New England Journal of Medicine, 362(3), 239-252.
Leme, D., Souza, D. H., Mercado, G., Pastene, E., Dias, A., & Moretti-Ferreira, D. (2013). Assessment of clinical scoring systems for the diagnosis of Williams-Beuren syndrome. Genetics and Molecular Research, 3407-3411.
Lowery, M. C., Morris, C. A., Ewart, A., Brothman, L. J., Zhu, X. L., Leonard, C. O & Brothman, A. R. (1995). Strong Correlation of Elastin Deletions, Detected by FISH, with Williams Syndrome: Evaluation of 235 Patients. American Journal of Human Genetics, 57(1), 49.
U.S. National Library of Medicine. (2015, July 01). Williams syndrome. Retrieved from http://www.nlm.nih.gov/medlineplus/ency/article/001116.html
CONTRIBUTORS
Causes written by Emily So and JungYoon Kim, Simon Fraser University. Detection & Diagnosis written by Kendra Wong, Simon Fraser University. Cite as: