In Reply In their response letter to an article in JAMA Neurology on newborn screening for fragile X syndrome, Godler and collaborators stated that there is a “contentious ethical issue [in] the detection of late-onset [premutation] conditions” (eg, fragile X–associated tremor/ataxia syndrome and fragile X–associated primary ovarian insufficiency) in infant carriers. However, newborn screening does not detect late-onset conditions, rather it only identifies the allele size of the FMR1 gene. From the most recent large screening studies,1,2 most of the identified carriers had alleles with low CGG repeat number, which are associated with relatively low risk for developing one of the late-onset conditions.
Tassone F. Methylation Analysis in Newborn Screening for Fragile X Syndrome—Reply. JAMA Neurol. 2014;71(6):800-801. doi:10.1001/jamaneurol.2014.454