Zhadina M, Roszko KL, Geels RES, et al. - In this retrospective cross-sectional analysis, researchers sought to ascertain if the most common GNAS variants (R201C and R201H) are correlated with a specific clinical phenotype and to determine the prevalence of the most common GNAS variants in a large patient cohort. Using DNA extracted from tissue or circulating cell-free DNA, 61 individuals were genotyped. In patients with the most common FD/MAS pathogenic variants, there is no strong genotype-phenotype link. The predominance of the R201H variant noted in the cohort and reported in the literature suggests that the larger population of patients with FD/MAS is likely to be responsible for a greater burden of disease, which could have major consequences for the potential development of targeted therapies.