Disclosed herein are methods and compositions for the treatment of facioscapulohumeral muscular dystrophy and other muscle diseases or disorders. In some cases, the methods and compositions involve the use of methyltransferase inhibitors to inhibit or repress DUX4 expression in muscle cells. Further disclosed herein are methods and cell based assays for screening compounds for the treatment of facioscapulohumeral muscular dystrophy and other muscle diseases.