Clinical features and genotypes of Laing distal myopathy in a group of Chinese patients, with in-frame deletions of MYH7
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RESEARCH
Clinical features and genotypes of Laing distal myopathy in a group of Chinese patients, with in‑frame deletions of MYH7 as common mutations Meng Yu1, Ying Zhu2, Yuanyuan Lu1, He Lv1, Wei Zhang1, Yun Yuan1 and Zhaoxia Wang1*
Abstract Background: Laing distal myopathy is a rare autosomal dominant inherited distal myopathy caused by mutations of the MYH7 gene affecting mainly the rod region. We described the clinical features, muscle MRI and pathological changes as well as genetic mutations in a group of Chinese patients with Laing distal myopathy. Results: Six patients with the confirmed diagnoses of Laing distal myopathy were recruited. Ankle dorsiflexion and finger extension weakness, as well as neck flexion weakness were common in our patients. Myopathic as well as neurogenic lesions were suggested by electromyography in different patients. Respiratory abnormality of sleep apnea was detected in two of our patients stressing the necessity of close respiratory monitoring in this disease. Muscle MRIs showed similar features of concentric fatty infiltration of anterior thigh muscles together with early involvement of tibialis anterior and extensor hallucis longus. However, muscle pathological presentations were varied depending on the biopsied muscles and the severity of the disease. In-frame deletions of the MYH7 gene made up 3/4 of mutations in our patients, suggesting that these are common mutations of Laing distal myopathy. Conclusions: Our study further expanded the phenotypes and genotypes of Laing distal myopathy. In-frame deletions of the MYH7 gene are common causes of Laing distal myopathy. Keywords: Laing distal myopathy, MYH7, Phenotype, Genotype, Pathology Background Myosin is a family of highly conserved proteins acting as a molecular motor, which provides mechanical forces in a variety of cellular movements including muscle contraction [1]. Muscle myosin is myosin II consisting of two myosin heavy chain (MyHC) subunits and two pairs of light chain subunits [2]. There are several MyHC isoforms of striated muscles which are expressed in different muscle types. Among these, slow/β-cardiac MyHC is *Correspondence: [email protected] 1 Department of Neurology, Peking University First Hospital, No. 8 Xishiku Street, Beijing 100034, China Full list of author information is available at the end of the article
encoded by MYH7, and is mainly expressed in slow, type 1 muscle fibers as well as in heart ventricles [3]. Slow/β-cardiac MyHC can be divided into two parts: the N-terminal globular head region made by amino acids 1-847, and the C-terminal rod region made by amino acids 848-1935 [4]. A variety of both cardiac and skeletal muscle disorders can be caused by MYH7 mutations. Mutations affecting the globular head region mainly cause cardiomyopathies, including familial hypertrophic/dilated cardiomyopathy, and left ventricular noncompaction (LVNC) cardiomyopathy, while mutations affecting the rod region mainly cause skeletal myopathies, including myosin storage myopathy (MSM), Laing di
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