摘要Down syndrome,Turner syndrome,and Klinefelter syn-drome are the most common chromosomal disorders world-wide.Down syndrome is caused by an extra copy of the 21st chromosome and has an incidence of 1 in 800 to 1000 live births.Turner syndrome results from X-chromosome monosomy and has an incidence of 1 in 2000 of live-born female infants.Klinefelter syndrome is caused by an extra X chromosome in male infants and has an incidence of 1 in 600 live-born male infants.All of these syndromes have greater liabilities for metabolic and cardiovascular comor-bidities[1].A complementary health care system is required for early detection of comorbidities among these children to improve their quality of life[2-5].Several non-traditional modifiable risk factors have been identified including homo-cysteinemia[6].Homocysteine is a sulfhydryl-containing amino acid produced as an intermediate product during the metabolism of methionine and cysteine.Homocysteine is considered as a key element of the methylation cycle[7].