Polymerase chain reaction (PCR) testing for fragile X syndrome identifies the presence and size of the CGG repeat expansion in the FMR1 gene. This genetic test determines whether an individual has a normal, premutation, or full mutation allele. Determining the sex of the individual being tested is essential for proper interpretation of these results, as the clinical presentation and risk of expansion from premutation to full mutation differ significantly between males and females. For example, females with a full mutation may demonstrate a wider range of symptom severity than males due to X-inactivation.
Genetic testing clarifies carrier status, predicts the likelihood of future generations inheriting the mutation, and guides reproductive decisions. Early diagnosis is crucial for implementing appropriate interventions and support services for affected individuals. Historically, diagnosing fragile X syndrome was challenging, relying primarily on clinical observation. PCR-based testing revolutionized diagnostic accuracy and enabled proactive genetic counseling.
