Kai Qiao

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 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.

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.

Isaacs syndrome with CASPR2 antibody: A series of three cases

Isaacs syndrome is a form of peripheral nerve hyperexcitability, characterized by spontaneous muscle twitching and stiffness. Some patients are reported to be positive for CASPR2 antibody that may be one of the pathogenic autoantibodies in Isaacs syndrome. We reported a series of three patients with Isaacs syndrome, including their clinical features, electrophysiologic findings, laboratory parameters and therapeutic responses. All the three patients were positive for CASPR2 antibodies examined on transfected human embryonic kidney 293 cells by indirect immunofluorescence method. One patient had invasive thymoma. Symptomatic treatment was not sufficient for them, while immunotherapies including corticosteroids, double filtration plasmapheresis and rituximab provided favorable outcomes. The titers of CASPR2 antibody decreased after immune modulating therapy in parallel to clinical improvements in two patients.

Novel LAMP2 mutations in Chinese patients with Danon disease cause varying degrees of clinical severity.

AIMS Danon disease is an Xlinked dominant lysosomal glycogen storage disorder characterized by cardiomyopathy, skeletal myopathy, and mental retardation. This study described two Chinese cases of Danon disease in order to broaden the phenotypic and genetic spectrum. METHODS Clinical data were collected and LAMP2 mutations were analyzed. RESULTS Patient A had fluctuating limb weakness during 6 months follow-up and was diagnosed with drug-induced myopathy due to anti-hepatitis B therapy with lamivudine. However, the first muscle biopsy with large cytoplasmic vacuoles confused the diagnosis and led to the second biopsy that allowed for the final diagnosis. Patient B had severe cardiac disturbances leading to sudden death. Molecularly, patient A harbored a synonymous mutation adjacent to the exon 6-intron 6 junction; mRNA analysis provided evidence that totally abolished the donor site and caused skipping of exon 6. Patient B harbored a frame-shift deletion mutation in exon 3 (c.396delA) leading to a truncated protein. DISCUSSION To our knowledge, this is the first report of Danon disease caused by a synonymous exon mutation that affected mRNA splicing, which indicates that a synonymous substitution may not be silent when it is in the exon sequences close to the splice sites. It is also the first description of Danon disease clinically presenting as druginduced myopathy at onset; the pathological changes might be the key point for making a differential diagnosis. *These two authors contributed equally to this work.

Novel SEA and LG2 Agrin mutations causing congenital Myasthenic syndrome

BackgroundCongenital myasthenic syndrome caused by mutations in AGRN, a gene encoding a protein with a crucial function at the neuromuscular junction, is a rare disorder. There are few studies in this area. We here present two cases with novel mutations of AGRN of which we further investigated possible pathogenesis.ResultsPatient 1 had general limb weakness with fluctuation and deterioration in the afternoon and in hot weather. Patient 2 had early-onset weakness of lower extremities with suspected fluctuation in the early stages, which then progressed to the upper limbs. Both distal and proximal muscles were involved. Repetitive stimulation on EMG in both patients showed decrement in proximal and distal limbs. Patient 2 showed a marked response to salbutamol while Patient 1 did not. By targeted exome sequencing, two novel homozygous missense variants, p.L1176P and p.R1698C, in the SEA and LG2 domain of agrin were identified respectively. Further functional analysis revealed instability of the protein and impaired clustering of the acetylcholine receptor (AChR) by both mutations.ConclusionsThe mutations identified in AGRN in our study may cause congenital myasthenic syndrome by damaging protein stability and interfering with AChR clustering. These results broaden the understandings on the phenotype, genotype and pathogenesis of this rare disorder.

Proximally evoked soleus H‐reflex to S1 nerve root stimulation in sensory neuronopathies (ganglionopathies)

Sensory neuronopathy (SNN) mimics distal sensory axonopathy. The conventional H‐reflex elicited by tibial nerve stimulation (tibial H‐reflex) is usually abnormal in both conditions. We evaluated the proximally evoked soleus H‐reflex in response to S1 nerve root stimulation (S1 foramen H‐reflex) in SNN.

Palpebral portion of the orbicularis oculi muscle to repetitive nerve stimulation testing: A potential assessment indicator in patients with generalized myasthenia gravis

Repetitive nerve stimulation (RNS) is a valuable diagnostic method for myasthenia gravis (MG). However, its association with clinical severity was scarcely studied. We reviewed medical records and retrospectively enrolled 121 generalized MG patients. Sensitivity of different muscles to RNS and clinical scoring systems was evaluated. RNS testing revealed facial muscles have the highest positive rate, followed by proximal muscles and distal muscles, with the palpebral portion of the orbicularis oculi muscle most sensitive. Amplitude decrement of compound muscle action potential (CMAP) in the palpebral portion of the orbicularis oculi muscle is related to quantitative myasthenia gravis (QMG) scores, MG-specific manual muscle testing (MMT) scores and myasthenia gravis-related activities of daily living (MG-ADL) scores. We suggest that RNS testing of the palpebral portion of the orbicularis oculi muscle is a potential assessment indicator in patients with generalized MG.

Clinical features and long exercise test in Chinese patients with Andersen-Tawil syndrome.

Introduction: Andersen‐Tawil syndrome (ATS) is a rare multisystem channelopathy characterized by periodic paralysis, ventricular arrhythmias, and developmental dysmorphology. There are few reports concerning ATS in the Chinese population. We analyzed clinical features and evaluated the long exercise test as a tool for diagnosis of periodic paralysis in ATS. Methods: Direct sequencing of KCNJ2 was performed in 12 subjects from mainland China with suspected ATS. Clinical features, therapeutic responses, and long exercise tests (LET) were retrospectively analyzed. Results: Twelve patients were genetically confirmed to have ATS. A small mandible and clinodactyly were demonstrated in all patients. Premature ventricular contractions were the most prevalent form of cardiac arrhythmia. The LET revealed an early amplitude decrement. Conclusions: Chinese ATS patients shared some common clinical features with reported subjects in other countries. An early amplitude decrement in LET may be useful for diagnosis of ATS. Muscle Nerve 54: 1059–1063, 2016