GNAL and Menkes disease: Whereas known monogenic causes of dystonia, i.e. TOR1A, THAP1 or GNAL, have been excluded as a major cause17–19, recent studies revealed RAB12 as a plausible candidate gene causing MD in 1.7% of patients20, and an intronic variant in the ARSG gene increasing the risk to develop MD to a factor of 4.3321.