Identification of Seven Novel Mutations in the Acid Alpha-glucosidase Gene in Five Chinese Patients with Late-onset Pompe Disease

Background： Pompe disease is a rare lysosomal glycogen storage disorder linked to the acid alpha-glucosidase gene （GAA）. A wide clinical and genetic variability exists between patients from different ethnic populations, and the genotype-phenotype correlations are still not well understood. The aim of this study was to report the clinicopathological and genetic characteristics of five Chinese patients with late-onset Pompe disease （LOPD） who carried novel GAA gene mutations. Methods： Clinical and pathological data of patients diagnosed with glycogen storage disease at our institution from April 1986 to August 2017 were collected, and next-generation sequencing of frozen muscle specimens was conducted. Results： Of the five patients included in the study, the median disease onset age was 13 years, with a median 5 years delay in diagnosis. The patients mainly manifested as progressive weakness in the proximal and axial muscles, while one patient developed respiratory insufficiency that required artificial ventilation. In muscle biopsies, vacuoles with variable sizes and shapes appeared inside muscle fibers, and they stained positive for both periodic acid-Schiff and acid phosphatase staining. Ten GAA gene mutations, including seven novel ones （c.796C〉A, c. 1057C〉T, c. 1201C〉A, c. 1780C〉T, c. 1799G〉C, c.2051C〉A, c.2235dupG）, were identified by genetic tests. Conclusions： The seven novel GAA gene mutations revealed in this study broaden the genetic spectrum of LOPD and highlight the genetic heterogeneity in Chinese LOPD patients.

A Novel Mutation of Mitochondrial T14709C Causes Myoclonic Epilepsy with Ragged Red Fibers Syndrome in a Chinese Patient

Background： Myoclonic epilepsy with ragged red fibers （MERRF） syndrome is characterized by myoclonus, generalized epilepsy, cerebellar ataxia, and ragged red fibers （RRFs） in the muscle. T-to-C transition at nucleotide position 14709 in the mitochondrial tRNA glutamic acid （tRNA^Gla） gene has previously been associated with maternally inherited diabetes and deathess. However, the association between MERRF and mitochondrial T14709C mutation （m.TI4709C） has never been reported before. Methods： Clinical information of a 17-year-old patient was collected; muscle biopsy and next-generation sequencing （NGS） of whole mitochondrial and neuromuscular disease panel were then conducted. Finally, sanger sequencing was carried out to confirm the mutations. Results： The patient presented a typical MERRF phenotype with muscle weakness, epileptic seizure, clonic episodes, cerebellar ataxia, and spinal scoliosis. Muscle biopsy showed RRFs which indicated abnormal mitochondrial functions. NGS of whole mitochondrial gene revealed m.TI4709C mutation, confirmed by Sanger sequencing. Conclusion： We present a sporadic patient with typical MERRF presentation carrying the mutation ofm.T14709C, which expanded the spectrum of re.T14709C.

Clinical,Pathological,and Genetic Features of Two Chinese Cases with Filamin C Myopathy

To the Editor:Filamin C (FLNC)myopathy is an autosomal dominant inherited myopathy caused by mutations in FLNC.FLNC belongs to the filamin superfamily and cross-links actin filaments to form a network,anchoring membrane protein to the cytoskeleton. Human protein filamins comprise three isoforms encoded by the human genome:filamins A,B,and C.Among these,FLNC is a Z-disk protein encoded by the FLNC gene and is mainly expressed in the skeletal and cardiac muscles.FLNC gene is on chromosome 7q32-q35,containing genomic DNA of about 29.5 kb length and 49 encoding exons.FLNC is an isoform of serine protease expressed primarily in the striated muscle,containing 2725 amino acids, at a molecular weight of 291,000.FLNC protein contains two domains.The amino terminus consists of two ealponin homology domains that together constitute the actin-binding domain (ABD), followed by 24 filamin-type immunoglobulin (Ig-FLMN)repeated domains (rod-overlapping domains),the most carboxy-terminal of which is responsible for dimerization,assembly,and anchor filaments.

Oculopharyngeal Weakness, Hypophrenia, Deafness, and Impaired Vision： A Novel Autosomal Dominant Myopathy with Rimmed Vacuoles

Background： Myopathies with rimnled vacuoles are a heterogeneous group of muscle disorders with progressive muscle weakness and varied clinical manifestations but similar features in muscle biopsies. Here, we describe a novel autosomal dominant myopathy with rimmed vacuoles in a large family with 11 patients of three generations affected. Methods： A clinical study including family history, obstetric, pediatric, and development history was recorded. Clinical examinations including physical examination, electromyography （EMG）, serum creatine kinase （CK）, bone X-rays, and brain magnetic resonance imaging （MRI） were performed in this family. Open muscle biopsies were performed on the proband and his mother. To find the causative gene, the whole-exome sequencing was carried out. Results： Disease onset was from adolescence to adulthood, but the affected patients of the third generation presented an earlier onset and more severe clinical manifestations than the older generations. Clinical features were characterized as dysarthria, dysphagia, external ophthalmoplegia, limb weakness, hypophrenia, deafness, and impaired vision. However, not every patient manifested all symptoms. Serum CK was mildly elevated and EMG indicated a myopathic pattern. Brain MRI showed cerebellum and brain stem mildly atrophy. Rimmed vacuoles and inclusion bodies were observed in muscle biopsy. The whole-exome sequencing was performed, but the causative gene has not been found. Conclusions： We reported a novel autosomal dominant myopathy with rimmed vacuoles characterized by dysarthria, dysphagia, external ophthalmoplegia, limb weakness, hypophrenia, deafness, and impaired vision, but the causative gene has not been tbund and needs further study.

Reply to ＂Mitochondrial tRNA Glutamic Acid Variant 14709T〉C Manifesting as Myoclonic Epilepsy with Ragged Red Fibers＂

Thank you for your attention and interest for our study, and thank you for your questions and opinions as well.