More recently, Metherell et al (2) demonstrated that mutations in melanocortin−2 receptor accessory protein (MRAP), encoding a new interacting partner of the ACTH receptor, caused FGD in 19 of 104 kindreds with confirmed FGD and no ACTH receptor mutations, and they account for a further 15–20% of FGD cases. The gene discussed is MC2R; the disease is Aarskog-Scott syndrome, X-linked.