G.p.56

Laing distal myopathy (LDM) is an autosomal dominant myopathy which is caused by mutation in the slow/beta cardiac myosin heavy chain ( MYH7 ) gene. It has been recently reported that LDM presents with a wide range of clinical manifestations. We herein report a large Chinese family with autosomal dominant myopathy. The affected individuals in the family presented foot drop at early childhood, and progressive distal and proximal limb weakness. Their characteristic symptoms were scapular winging and scoliosis in early disease phase, and impairment of ambulation in advanced phase. At first, we had suspected limb girdle muscular dystrophy (LGMD), but had not reached a correct diagnosis. Next, we performed linkage analysis and detected four linkage regions on chromosomes 1q23.2-24.1, 14q11.2-12, 15q26.2-26.3 and 17q24.3. Through whole exome sequencing, we found a de novo p.K1617del causative mutation in the MYH7 gene. Therefore, we have diagnosed the disease as LDM, which is the first case in China. Our patients had more severe clinical manifestations by mimicking LGMD in comparison with the patients with the same mutation reported elsewhere.