Emerinopathy and laminopathy clinical, pathological and molecular features of muscular dystrophy with nuclear envelopathy in Japan.

Mutations in the genes for nuclear envelope proteins of emerin (EMD) and lamin A/C (LMNA) are known to cause Emery-Dreifuss muscular dystrophy (EDMD) and limb girdle muscular dystrophy (LGMD). We compared clinical features of the muscular dystrophy patients associated with mutations in EMD (emerinopathy) and LMNA (laminopathy) in our series. The incidence of laminopathy was slightly higher than that of emerinopathy. The age at onset of the disease in emerinopathy was variable and significantly older than in laminopathy. The initial symptom of emerinopathy was also variable, whereas nearly all laminopathy patients presented initially with muscle weakness. Calf hypertrophy was often seen in laminopathy, underscoring the importance of mutation screening for LMNA in childhood muscular dystrophy with calf hypertrophy. The clinical spectrum of emerinopathy is actually wider than previously known including EDMD, LGMD, conduction defects with minimal muscle/joint involvement, and their intermittent forms. Pathologically, no marked difference was observed between emerinopathy and laminopathy. Increased number and variation in size of myonuclei were detected. More precise observations using electron microscopy is warranted to characterize the detailed nuclear changes in nuclear envelopathy.