CONTEXT: Turner syndrome (TS) is the most common genetic problem affecting women 
and occurs when an X chromosome is completely deleted, portions of an X 
chromosome are deleted, or chromosomal mosaicism occurs. Girls with TS may also 
have occult Y chromosome sequences. Whereas some girls with TS are identified in 
infancy or early childhood, many girls with TS are not detected until after 10 
yr of age, resulting in delayed evaluation and treatment.
OBJECTIVE: To prevent the delayed recognition and treatment of TS, a 
quantitative method of genotyping that can be performed as part of newborn 
screening is needed.
DESIGN: To screen for sex chromosome abnormalities, we assembled a panel of 
informative single nucleotide polymorphism (SNP) markers that span the X 
chromosome from the dbSNP database. Pyrosequencing assays suitable for 
quantitative assessment of signal strength from single nucleotides were designed 
and used to genotype 46,XX; 46,XY; 45,X; and TS mosaics, examining zygosity and 
signal strength for individual alleles. Pyrosequencing assays were also designed 
for the detection of Y chromosome material.
RESULTS: With just four informative SNP markers for the X chromosome, all TS 
girls with 45,X, partial X chromosome deletions, or mosaicism were identified 
with 100% sensitivity. In mosaic individuals, Y chromosomal material was 
detected with 100% sensitivity.
CONCLUSION: These results suggest that inexpensive high-throughput screening is 
possible for TS and other sex chromosome disorders using quantitative genotyping 
approaches.