RYR1 and multiminicore myopathy: Several neuromuscular diseases strongly associated with MH susceptibility include central core disease, multiminicore myopathy, congenital myopathy with cores and rods, and centronuclear myopathy, all of which are linked to mutations in ryanodine receptor 1 (RYR1).[2–5] Myotonic dystrophy type I (dystrophia myotonia type 1, DM1; Steinert disease) is a slowly progressive hereditary muscular disorder characterized by weakness and wasting of involved muscles, usually of the cranial musculature including facial, sternocleidomastoid (SCM), and distal limb muscles.