概述
Fragile X syndrome (an FMR1–related disorder) is the most commonly
inherited form of mental retardation. Early physical recognition is difficult,
so boys with developmental delay should be strongly considered
for molecular testing. The characteristic adult phenotype usually does
not develop until the second decade of life. Girls can also be affected
with developmental delay. Because multiple family members can be
affectedwithmentalretardationandotherconditions