Several X-linked developmental syndromes are associated with hemizygous MED12 variants, including Opitz–Kaveggia syndrome (FG syndrome, MIM 305450), Lujan–Fryns syndrome (MIM 309520), and X-linked Ohdo syndrome (MIM 300895), as well as non-syndromic X-linked ID [18]. The gene discussed is MED12; the disease is FG syndrome.