TTN and tibial muscular dystrophy: Autosomal dominant TTN mutations cause 2 adult onset skeletal muscle disorders: (1) tibial muscular dystrophy (TMD; OMIM #600334)11 and (2) hereditary myopathy with early respiratory failure (HMERF; OMIM #603689).12, 13 All reported TMD mutations are within the final 6 (M‐band) exons.