health

The diagnosis of fragile X syndrome is based on a combination of family
history, early signs of mental retardation in the child, and specific genetic
testing. Patients who have several mentally retarded male relatives or a
mother with mental retardation or learning disabilities are sometimes
screened on the basis of this family history. In other cases the child may
not be diagnosed until he or she has started school and his or her learning
disabilities become apparent. The standard diagnostic test for fragile X
syndrome is a DNA test that was developed in 1992. It counts the
number of repetitions in the FMR1 gene and can detect carriers of the
mutation as well as fully affected persons. The doctor takes a sample of
the patient’s blood and sends it to a laboratory for analysis. The test is
expensive but is often covered by health insurance.