Sushan Luo

Clinical features and ETFDH mutation spectrum in a cohort of 90 Chinese patients with late-onset multiple acyl-CoA dehydrogenase deficiency

The major cause of lipid storage myopathies (LSM) in China is multiple acyl-CoA dehydrogenase deficiency (MADD) caused by ETFDH mutations. We here present an analysis of the spectrum of ETFDH mutations in the largest cohort of patients with MADD (90 unrelated patients). We identified 61 ETFDH mutations, including 31 novel mutations, which were widely distributed within the coding sequence. Three frequent mutations were identified: c.250G > A (most common in South China), c.770A > G and c.1227A > C (most common in both South and North China). Regional differences of allele frequency and further haplotype analysis suggest the possibility of founder effects of c.250G > A and c.770A > G. These findings promise to provide the basis for implementing a rapid and economical strategy for diagnosing MADD.

Muscle pathology and whole-body MRI in a polyglucosan myopathy associated with a novel glycogenin-1 mutation

We report a 46-year-old female with late-onset skeletal myopathy affecting proximal limb muscles. Muscle biopsy revealed a polyglucosan myopathy with PAS-positive inclusions predominantly in glycogen-depleted fibers, which were demonstrated as type I fibers by ATPase staining. Whole-body magnetic imaging disclosed that the paravertebral, scapular, and pelvic girdle muscles, the anterior compartment of the arms, and the posterior compartment of the thighs were preferentially involved. Genetic analysis revealed a homozygous novel mutation in exon 6 of the glycogenin-1 gene (GYG1) (c.634C>T, p.His212Tyr). Protein analysis revealed normal levels of glycogenin-1 even before alpha-amylase digestion indicating preserved protein expression but impaired glucosylation. In vitro functional assay demonstrated that this variant impaired the autoglucosylating ability resulting in a non-functional protein. We report a glycogenin-1 related myopathy with a distinct histopathology and unique muscle imaging pattern.

HLA-DQA1*03:02/DQB1*03:03:02 is strongly associated with susceptibility to childhood-onset ocular myasthenia gravis in Southern Han Chinese☆

OBJECTIVE Our aim was to investigate the correlation between onset age, clinical features and HLA-DQA1/DQB1 genetic variability in myasthenia gravis (MG) patients in Southern Han Chinese. METHODS 205 MG patients and 100 controls were genotyped for HLA-DQA1 and -DQB1 using sequence-based typing (SBT) and analyzed for haplotype frequencies. Anti-acetylcholine receptor (AChR) autoantibodies were measured in all, and muscle-specific tyrosine kinase (MuSK) antibodies were tested in AChR antibody negative patients. RESULTS HLA-DQA1/DQB1 haplotypes showed association only with childhood-onset MG. Haplotype DQA1*03:02/DQB1*03:03:02 (DQ9) was positively associated with the childhood-onset MG, while haplotype DQA1*02:01/DQB1*02:02 and DQA1*05:01:01/DQB1*02:01:01 (DQ2) were negatively associated with this group. Childhood-onset ocular MG patients had an extremely high phenotype frequency of DQ9 haplotype (90.1% of patients, 34.0% of controls, p≤0.0001, OR=17.8). CONCLUSIONS The childhood-onset ocular MG in Southern Han Chinese may present a particular subgroup of distinct genetic background. Its correlation to the HLA haplotype DQA1*03:02/DQB1*03:03:02 might explain the phenotypic difference of MG between Han Chinese and Caucasians.

Novel mutations m.3959G>A and m.3995A>G in mitochondrial gene MT-ND1 associated with MELAS.

Abstract Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) are progressive neurodegenerative disorder associated with polygenetic, maternally inherited mutations in mitochondrial DNA. Approximately 80% of MELAS cases are caused by the mutation m.3243A>G of the mitochondrial tRNALeu (UUR) gene (MT-TL1). We reported two probands with MELAS features. Muscle biopsy identified ragged-red fibers (RRF) in Gomori Trichrome staining. A respiratory chain function study showed decreased activity of mitochondrial respiratory chain complex I in both probands. Sequencing of the mitochondrial DNA revealed two novel MT-ND1 gene missense mutations, m.3959G>A and m.3995A>G, which are highly conserved among species. Protein secondary structure predictions demonstrated that these mutations may alter the peptide structure and may lead to decreased ND1 gene stability. Our findings suggest that these two novel mutations may contribute to the MELAS phenotypes of the patients in our study.

Identification of LAMP2 Mutations in Early-Onset Danon Disease With Hypertrophic Cardiomyopathy by Targeted Next-Generation Sequencing.

Danon disease is an X-linked disorder with the clinical triad of cardiomyopathy, skeletal myopathy, and mental retardation. Early diagnosis of this disease remains a challenge, especially in the pediatric population. In this study, we developed a targeted panel-based next generation sequencing pipeline to identify mutations by sequencing of selected candidate genes in 136 pediatric patients with either hypertrophic cardiomyopathy (HC) or idiopathic dilated cardiomyopathy (IDC). This led to the identification of lysosome-associated membrane protein 2 (LAMP2) mutations in 4 of the 64 (6%) probands with HC, including 3 novel nonsense mutations (p.Q240X, p.S250X, and p.G22X). No LAMP2 mutation was detected in the other 72 probands with IDC. All 4 probands and one additional affected family member (2 men and 3 women) had an early-onset age and presented either HC alone or combined with Wolff-Parkinson-White syndrome and skeletal myopathy. Immunofluorescence staining and Western blot analysis revealed absent LAMP2 expression in both cardiac and skeletal muscle samples of the first proband and severely decreased LAMP2 expression in the skeletal muscle samples of the second proband. In conclusion, cardiomyopathy in the patients with Danon disease may occur during early childhood and tend to be HC rather than IDC in both affected men and women. Therefore, Danon disease should be considered as one of the leading causes of unexplained ventricular hypertrophy in pediatric patients. The inclusion of LAMP2 gene in cardiomyopathy genetic screening panels may contribute to early diagnosis of Danon disease.

Clinical and pathological features in 15 Chinese patients with calpainopathy.

Background: Calpainopathy is comprised of a group of myopathies caused by deficiency in calcium‐activated, neutral protease (calpain‐3). In this study we identify calpainopathy in a cohort of Chinese patients with unclassified myopathy and analyze its clinical and pathological features. Methods: Sixty‐six muscle biopsies were selected for combined Western blotting of dysferlin and calpain‐3 after immunohistochemical staining. Clinical and pathological parameters of 15 confirmed calpainopathy cases were determined. Results: The diagnosis of calpainopathy in 15 Chinese patients was confirmed by Western blot analysis. Fourteen subjects had progressive proximal muscle weakness; 1 presented with bilateral distal muscle atrophy of the lower extremities. Scapular winging was observed in 12 patients (80%), and joint contractures were found in 10 others (66.7%). Histopathological studies showed a high prevalence of lobulated fibers (66.7%). Conclusions: Chinese patients with calpainopathy share some common clinical and pathological features with the reported characteristics of non‐Chinese patients. Muscle Nerve, 2011

Novel mutations in the C-terminal region of GMPPB causing limb-girdle muscular dystrophy overlapping with congenital myasthenic syndrome

Mutations in the GMPPB gene may underlie both limb girdle muscular dystrophy (LGMD) and congenital myasthenic syndrome (CMS). Forty-one cases have been reported to date and hotspot mutations are emerging in the Caucasian population. Clinical and pathological features of 5 patients with compound heterozygous GMPPB mutations were collected and retrospectively reviewed. In vitro functional analysis was performed to investigate the pathogeneity of GMPPB variants. The patients presented with proximal limb weakness in their first to second decades. Fluctuating muscle weakness, myalgia and calf hypertrophy were the major complaints. Myogenic changes on electromyography and marked attenuation on 3 Hz repetitive nerve stimulation were observed in all patients. Four reported a beneficial response to pyridostigmine. Muscle MRI showed selective involvement in the calf in case 1. Immunolabeling of α-dystroglycan was abnormal for case 1 and case 2. Four novel missense mutations in the C-terminal region of GMPPB were identified, with p.(Arg357His) being present in all the cases. In vitro functional assays demonstrated that these variants did not markedly reduce the amount of GMPPB, but gave rise to an increased propensity for protein aggregation. Increasingly, patients with GMPPB mutations are found to present with an overlapping LGMD/myasthenic syndrome. The mutation spectrum in Chinese patients may differ from that of European populations, with the mutation p.(Arg357His) most frequently found. These mutations may lead to abnormal folding of GMPPB leading to protein aggregates in the cytoplasm rather than an overall loss in protein expression.

Clinical heterogeneity and a high proportion of novel mutations in a Chinese cohort of patients with dysferlinopathy.

BACKGROUND AND AIMS Dysferlinopathies are a group of autosomal recessive muscular dystrophies caused by mutations in the dysferlin gene. This study presents clinical features and the mutational spectrum in the largest cohort of Chinese patients analyzed to date. PATIENTS AND METHODS A total of 36 unrelated Chinese patients with diagnostic suspicion of dysferlinopathy were clinically and genetically characterized. RESULTS Patients were divided into five phenotypes: 19 patients with limb girdle muscular dystrophy (LGMD) type 2B, 10 with Miyoshi myopathy (MM), 1 with distal anterior compartment myopathy (DACM), 3 with exercise intolerance, and 3 with asymptomatic hypercreatine phosphokinasemia (hyperCPKemia). Thirty-one patients showed an absence or drastic reduction of dysferlin expression by Westernblot. Forty-three mutations were identified in DYSF, including 31 novel. CONCLUSION Our study underlines clinical heterogeneity and a high proportion of novel mutations in Chinese patients affected with dysferlinopathy.

Genetic variability and clinical spectrum of Chinese patients with limb-girdle muscular dystrophy type 2A

Previous studies of limb‐girdle muscular dystrophy type 2A (LGMD2A) patients in many countries have suggested a heterogeneous genetic and clinical spectrum, but the genotypes and phenotypes of Chinese LGMD2A patients remain unclear.

Giant cell polymyositis associated with myasthenia gravis and thymoma

We report a case of a 40-year-old woman who developed generalized muscle weakness over a period of 2 months. Physical examination revealed palpable masses in her arms and hands. Serum creatine kinase levels were elevated. Electromyography showed myopathic changes and 3 Hz repetitive nerve stimulation revealed a decremental pattern on repetitive nerve stimulation. Muscle MRI demonstrated increased signal intensity in the biceps brachii on T1-weighted images. Chest CT scan showed a mediastinal mass suggestive of thymoma. Muscle biopsy revealed giant cell polymyositis. The patient was treated with cholinesterase inhibitors and corticosteroids with improvement of strength, and subsequently underwent thymectomy followed by radiotherapy.