How does genetic testing inform family planning in X-linked muscular dystrophy?

• A. Carrier testing of female relatives helps assess risk to future sons and informs reproductive decisions
• B. It predicts exact onset age
• C. It is not useful for family planning
• D. It only confirms diagnosis in affected individuals

Answer: (A)

Understanding how this disease is inherited helps explain why testing female relatives matters for family planning. X-linked muscular dystrophy is passed through the X chromosome. Males have a single X, so if they inherit the mutated gene they typically become affected. Females have two X chromosomes; a woman who carries one copy of the mutated gene may be asymptomatic or mildly affected but can pass the gene to her children. If a mother is a carrier, each pregnancy carries about a 50% chance the son will be affected and a 50% chance the daughter will be a carrier. Identifying carrier status among female relatives provides crucial information for estimating the risk to future sons and for making informed reproductive choices, such as prenatal testing, preimplantation genetic diagnosis, or using donor eggs. Genetic testing can guide planning even though it won’t pinpoint the exact age of onset or disease severity.