Abstract
Nemaline myopathy (NM) is a congenital myopathy of great heterogeneity, characterized by the presence of rods in the cytoplasm of muscle fibers. The samples of 16 nemaline myopathy patients diagnosed by characteristically pathological features went through whole exon sequencing. Clinico-pathological and genetic features of the cases were systematically analyzed. According to the classification of nemaline myopathy by ENMC, 8 cases are typical congenital subtype, 6 cases are childhood/juvenile onset subtype and 2 case are adult onset subtype. In histological findings, characteristic purple-colored rods are discovered under modified gömöri trichrome staining (MGT). Electron microscopy revealed the presence of high electron-dense nemaline bodies around the submucosa and the nucleus nine patients (9/16 56.3%) were detected pathogenic causative mutations, among whom mutations in the NEB gene were the most frequent (6 patients, 66.7%). KBTBD13 gene mutation was discovered in two patients and ACTA1 gene mutation was discovered in 1 patient. Nemaline myopathy is a congenital myopathy with highly clinico-pathological and genetic heterogeneity. NEB gene mutation is the most common mutation, in which splicing change c.21522 +3A > G is hotspot mutation in Chinese NM patients.
Highlights
Nemaline myopathy (NM) is a common type of congenital myopathy, which is named by the presence of rod-like structures in skeletal muscle fibers [1, 2]
Proximal muscle weakness is characteristic in nemaline myopathy, while some patients suffer from distal muscle weakness, which suggests the heterogeneity of clinical manifestation and brings challenge for the diagnosis of nemaline myopathy
Case 7 and 11 in our study showed distal muscle weakness with NEB gene mutations, which is in accordance with the study by Kiiski, who reported distal nemaline/cap myopathy with a large deletion in the nebulin gene [16]
Summary
Nemaline myopathy (NM) is a common type of congenital myopathy, which is named by the presence of rod-like structures in skeletal muscle fibers [1, 2]. In 2000, European Neuromuscular Center (ENMC) International Consortium defined six types of NM according to different clinical manifestations [3]: severe, intermediate, typical congenital, childhood/juvenile onset, adult onset and other unusual. We have systematically reviewed the clinical and pathological features of nemaline myopathy patients in China [14]. There is no systemic research on the genetic features of nemaline myopathy patients in China until now. In order to investigate the clinical features and mutational spectrum of nemaline myopathy in China, we present 16 nemaline myopathy cases from our neuromuscular disease database with clinico-pathological and genetic data
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