MED12 and Leigh syndrome: Pathogenic variants in the MED12 gene cause multiple X-linked recessive disorders including FG syndrome type 1 (FGS1, MIM: #305450), Lujan syndrome (LS, MIM: #309520), X-linked Ohdo syndrome (XLOS, MIM: #300895), and non-specific intellectual disability (NSID) (Lyons, 1993).