An expansion of a CGG trinucleotide repeat in the 5' untranslated region of the FMR1 gene is associated with FMR1-Related Disorders including Fragile X Syndrome, Fragile X Ataxia Syndrome (FXTAS) and Fragile-X Associated Primary Ovarian Insufficiency (POI). A full mutation (>200 repeats) is associated with fragile X syndrome which is typically characterized by moderate to severe intellectual disability in affected males and mild intellectual disability in affected females. Characteristic facial features include a long narrow face, large ears, a prominent jaw and forehead. Additional features include autism spectrum disorder and developmental delay. Male carriers of a premutation (55-200 repeats) have up to a 75% lifetime risk of developing FXTAS, while females carriers of a premutation have an 8% to 17% risk of developing FXTAS. Female carriers of a premutation also have a 21% risk of developing POI which is defined as defined as cessation of menses before age 40 years.