FGD1 and faciodigitogenital syndrome: For example, missense variants in the DH domain of FGD1 cause Aarskog–Scott syndrome (Orrico et al., 2004; Pérez-Coria et al., 2015), while the DH domain variants in FGD4 lead to Charcot–Marie–Tooth disease type 4H (CMT4H) (Hyun et al., 2015).