How does Arts syndrome run in families?
Arts syndrome is inherited in an X-linked pattern. Arts syndrome is caused by an unexpected change, called a mutation, in a gene called PRPS1. People have about 20,000-25,000 genes in their bodies. Genes contain our body's genetic information (called DNA) and they are like our body's instruction manual. When there is a mutation in PRPS1, it cannot work properly. It is like a section of the body's instruction manual is not correct, and it causes problems with the normal development and functioning of the body, resulting in Arts syndrome.
Genes are packaged into microscopic structures called chromosomes. Chromosomes are found in almost every cell of a person's body. Human cells usually contain 46 chromosomes, or 23 pairs of chromosomes. One chromosome of each pair is inherited from our mother, and the other is inherited from our father. The first 22 pairs of chromosomes are numbered 1-22, and they are the same in males and females. The last pair are called the sex chromosomes and they determine our gender. Females have two X chromosomes (XX) and males have one X chromosome and one Y chromosome (XY).
The PRPS1 gene is located on the X chromosome. Because boys only have one copy of the X chromosome, they also have only one copy of the PRPS1 gene. If boys have a mutation in this gene they will have Arts syndrome. Since females have two copies of the X chromosome, they also have two copies of the PRPS1 gene. If a female has one copy of the PRPS1 gene with a mutation, her other working copy of the PRPS1 gene can mask the effects of the altered gene. As a result, many females with a PRPS1 mutation will not develop any symptoms of Arts syndrome. For those that do, their symptoms are much more mild compared to boys with Arts syndrome. Women who have a mutation in one PRPS1 gene are called "carriers" for Arts syndrome.
Every time a woman has a child, she passes on only one of her X chromosomes to each child. This means that women who are carriers for Arts syndrome pass on only one of their copies of the PRPS1 gene to each child - there is a 50%, or 1 in 2, chance that she will pass on her working copy of the PRPS1 gene, and a 50%, or 1 in 2, chance that she will pass on her non-working copy of the PRPS1 gene. We have no control over which genes we pass onto our children; it is completely random. If a woman passes on a non-working PRPS1 gene to a son, he will have Arts syndrome. If a woman passes on a non-working PRPS1 gene to a daughter, she will be a carrier for Arts syndrome like her mother. Because Arts syndrome causes such severe symptoms, most boys with the disorder pass away in childhood. As a result, there are no reports of males with Arts syndrome having children.
A genetic counselor can help explain X-linked inheritance and how Arts syndrome is passed from generation to generation in families. Genetic counselors in the United States can be found on the National Society of Genetic Counselors website. Genetic counselors in Canada can be found at the Canadian Association of Genetic Counselors website.
de Brouwer APM, Duley JA, Christodoulou J. Arts syndrome. 2008 Oct 21 [Updated 2011 Mar 29]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2016. Available from: http://www.ncbi.nlm.nih.gov/books/NBK2591/http://ghr.nlm.nih.gov/condition/arts-syndrome
"Arts syndrome." Genetics Home Reference. Sept 2014. Web. 14 June 2016. https://ghr.nlm.nih.gov/condition/arts-syndrome#inheritance