How is cystinosis inherited?
Cystinosis is inherited in an autosomal recessive manner through a family. Everyone has two copies of the CTNS gene; one received from their father and one from their mother. Autosomal recessive inheritance means that in order to have the disease, a person must receive a nonworking copy of the CTNS gene from both parents. The parents have one working copy of the gene and one nonworking copy; they are carriers for cystinosis. Carriers, also known as heterozygotes, do not develop symptoms of the disorder. In order to cause cystinosis, both parents must pass along a nonworking copy of the CTNS gene in order for their child to have cystinosis. For each individual pregnancy, there is a 25% chance that both parents will pass along a nonworking copy of the CTNS gene and the child will have the disorder. There is a 50% chance that one parent will pass on the gene change and the other won't, meaning the child will be a carrier for the disorder. There is a 25% chance that both parents will pass along a working copy of the gene and the child will not have the disorder and will not be a carrier.
Nephropathic Cystinosis. Online Mendelian Inheritance in Man (OMIM) website. http://omim.org/entry/219800. Updated August 30, 2012. Accessed March 22, 2016.