Although FGD1 variant is the only known cause of AAS, there are only about 20% of AAS patients who were confirmed to have variants in FGD1, which may be due to the presence of undetected FGD1 variants or the involvement of epigenetic or exogenous causes in the pathogenesis of AAS [5, 13]. The gene discussed is FGD1; the disease is Aarskog-Scott syndrome, X-linked.