When stratified by sex, the association between plasma S1P levels and CAN exhibited a sex difference; in multivariable analysis, plasma S1P levels were significantly associated with CAN in women (odds ratio per standard deviation increase in the log-transformed value, 0.40; 95% confidence interval, 0.23–0.70, p = 0.001). This evidence concerns the gene MBTPS1 and Crouzon syndrome-acanthosis nigricans syndrome.