Schematic diagram showing the locations of all MC2R mutations that are known to be associated with FGD type 1. Those shown in red are missense mutations, those in blue are probable benign polymorphisms, and those in green are nonsense or frameshift mutations. (Reprinted from Clark AJ, Metherell LA, Cheetham ME, Huebner A. Inherited ACTH insensitivity illuminates the mechanisms of ACTH action. Trends Endocrinol Metab, 2005; 16: 451–7 (10) with permission.) (See also Fig. 5.10.1)