MTM1 and obesity due to melanocortin 4 receptor deficiency: Major genes within the deleted region include FMR1, FMR2, IDS, MTM1 and MTMR1. In addition to Hunter syndrome and myotubular myopathy, other phenotypic abnormalities noted in other individuals with contiguous gene deletions including the FMR1 are obesity [21,22,24], cherubism [23], overgrowth [25,26], and macrocephaly [27,28].