TOR1A and Menkes disease: More than 50 genes have now been identified as causative for the inherited forms of dystonia, with examples including ANO3, GNAL, GNAO1, THAP1, and TOR1A. Myoclonus Dystonia (MD) is another such inherited form of dystonia, caused by mutations in the SGCE gene that encodes the ε-sarcoglycan protein, and is inherited in an autosomal dominant fashion but with reduced penetrance owing to maternal imprinting.