Expansion of GGC Repeat in GIPC1 Is Associated with Oculopharyngodistal Myopathy.

Oculopharyngodistal myopathy (OPDM) is an adult-onset inherited neuromuscular disorder characterized by progressive ptosis, external ophthalmoplegia, and weakness of the masseter, facial, pharyngeal, and distal limb muscles. The myopathological features are presence of rimmed vacuoles (RVs) in the muscle fibers and myopathic changes of differing severity. Inheritance is variable, with either putative autosomal-dominant or autosomal-recessive pattern. Here, using a comprehensive strategy combining whole-genome sequencing (WGS), long-read whole-genome sequencing (LRS), linkage analysis, repeat-primed polymerase chain reaction (RP-PCR), and fluorescence amplicon length analysis polymerase chain reaction (AL-PCR), we identified an abnormal GGC repeat expansion in the 5' UTR of GIPC1 in one out of four families and three sporadic case subjects from a Chinese OPDM cohort. Expanded GGC repeats were further confirmed as the cause of OPDM in an additional 2 out of 4 families and 6 out of 13 sporadic Chinese individuals with OPDM, as well as 7 out of 194 unrelated Japanese individuals with OPDM. Methylation, qRT-PCR, and western blot analysis indicated that GIPC1 mRNA levels were increased while protein levels were unaltered in OPDM-affected individuals. RNA sequencing indicated p53 signaling, vascular smooth muscle contraction, ubiquitin-mediated proteolysis, and ribosome pathways were involved in the pathogenic mechanisms of OPDM-affected individuals with GGC repeat expansion in GIPC1. This study provides further evidence that OPDM is associated with GGC repeat expansions in distinct genes and highly suggests that expanded GGC repeat units are essential in the pathogenesis of OPDM, regardless of the genes in which the expanded repeats are located.

Anti-TIF1-γ antibody and cancer-associated myositis: A clinicohistopathologic study.

OBJECTIVE: We aimed to analyze the clinical and histopathologic features of cancer-associated myositis (CAM) in relation to anti-transcriptional intermediary factor 1 γ antibody (anti-TIF1-γ-Ab), a marker of cancer association. METHODS: We retrospectively studied 349 patients with idiopathic inflammatory myopathies (IIMs), including 284 patients with pretreatment biopsy samples available. For the classification of IIMs, the European Neuromuscular Center criteria were applied. Patients with CAM with (anti-TIF1-γ-Ab[+] CAM) and without anti-TIF1-γ-Ab (anti-TIF1-γ-Ab[-] CAM) were compared with patients with IIM without cancers within and beyond 3 years of myositis diagnosis. RESULTS: Cancer was detected in 75 patients, of whom 36 (48%) were positive for anti-TIF1-γ-Ab. In anti-TIF1-γ-Ab(+) patients with CAM, cancers were detected within 1 year of myositis diagnosis in 35 (97%) and before 1 year of myositis diagnosis in 1. All the anti-TIF1-γ-Ab(+) patients with CAM satisfied the dermatomyositis (DM) criteria, including 2 possible DM sine dermatitis cases, and were characterized histologically by the presence of perifascicular atrophy, vacuolated fibers (VFs), and dense C5b-9 deposits on capillaries (dC5b-9). In contrast, 39 anti-TIF1-γ-Ab(-) patients with CAM were classified into various subgroups, and characterized by a higher frequency of necrotizing autoimmune myopathy (NAM). Notably, all 7 patients with CAM classified into the NAM subgroup were anti-TIF1-γ-Ab(-) and exhibited no dC5b-9 or VFs. CONCLUSIONS: CAM includes clinicohistopathologically heterogeneous disease entities. Among CAM entities, anti-TIF1-γ-Ab(+) CAM has characteristically shown a close temporal association with cancer detection and the histopathologic findings of dC5b-9 and VFs, and CAM with NAM is a subset of anti-TIF1-γ-Ab(-) CAM.

Chronic Myopathy Associated With Anti-Signal Recognition Particle Antibodies Can Be Misdiagnosed As Facioscapulohumeral Muscular Dystrophy.

OBJECTIVES: To report cases of chronic autoimmune necrotizing myopathy with anti-signal recognition particle antibodies (anti-SRP myopathy) initially misdiagnosed as muscular dystrophy, in particular, facioscapulohumeral muscular dystrophy (FSHD). METHODS: Medical records of patients with anti-SRP myopathy in our institution were retrospectively reviewed. RESULTS: All 6 patients were initially diagnosed with muscular dystrophy because of the long-term clinical course and lack of inflammation on biopsy; 5 were diagnosed with FSHD based on a winged scapula. However, the following features suggested an alternative diagnosis, leading to anti-SRP antibody measurement: (1) lack of family history, (2) lack of facial involvement and asymmetry, (3) prominent dysphagia, and (4) profuse spontaneous activities on needle electromyography. All patients showed improvement with immunomodulating therapy. CONCLUSIONS: Anti-SRP antibody measurement should be considered in patients diagnosed with FSHD if they present with diagnostic hallmarks of anti-SRP myopathy listed above, to avoid oversight of this potentially treatable disorder.

Sporadic late-onset nemaline myopathy as a rare cause of slowly progressive muscle weakness with young adult onset.

INTRODUCTION: Sporadic late-onset nemaline myopathy (SLONM) is a rare intractable acquired myopathy characterized by progressive muscle weakness and atrophy, usually with middle to late adult onset. Autologous peripheral blood stem cell transplantation (auto-PBSCT) has been reported to be a promising treatment for SLONM. METHODS: In this study we performed clinical characterization, muscle histopathological analysis, and muscle power monitoring after auto-PBSCT in a 27-year-old HIV-negative man with monoclonal gammopathy. RESULTS: He showed improved muscle strength after treatment with high-dose melphalan and auto-PBSCT. CONCLUSIONS: Considering the recent reports of successful treatment of SLONM, early and correct diagnosis of this condition in association with monoclonal gammopathy is important. SLONM should be added to the list of diseases to consider in the differential diagnosis of progressive muscle weakness with young adult onset.

Inflammatory myopathies associated with anti-mitochondrial antibodies.

Anti-mitochondrial antibodies, the characteristic markers of primary biliary cirrhosis, have been detected in most patients with this disease. However, the prevalence of these antibodies in inflammatory myopathies and their clinical and histopathological significance has not been determined. Sera from 212 consecutive patients with inflammatory myopathies were screened for anti-mitochondrial antibodies by enzyme-linked immunosorbent assay. The clinical and histopathological features of anti-mitochondrial antibody-positive patients were analysed and statistically compared with those of anti-mitochondrial antibody-negative patients. Twenty-four patients positive for anti-mitochondrial antibodies (seven patients with and 17 patients without primary biliary cirrhosis) were identified (11.3%). Thirteen patients had a clinically chronic disease course of >12 months before their diagnosis at hospitals. Six of these 13 patients (four asymptomatic patients with increased creatine kinase levels and two patients with arrhythmia) had not been aware of muscle weakness, but all 13 patients had muscle atrophy at initial presentation. As complications, eight patients had cardiac involvement including arrhythmias (five patients with supraventricular tachycardia; two with ventricular tachycardia; and one patient with atrioventricular block), six patients had moderately decreased ejection fraction and six patients had decreased vital capacity, two of whom required respiratory support. Regarding muscle histopathological findings, in addition to inflammation, 13 patients had chronic myopathic changes and six had granulomatous lesions. Statistical analysis showed that the clinical features of a chronic disease course, cardiac involvement and muscle atrophy, and the histopathological features of chronic myopathic changes and granulomatous inflammation, were significantly more frequently observed in patients with anti-mitochondrial antibody-positive inflammatory myopathy than in patients who were negative for anti-mitochondrial antibodies. Except for cardiac involvement, which is more frequently observed in patients with primary biliary cirrhosis, no significant differences in clinical or histopathological features were found between patients with or without primary biliary cirrhosis. Our study revealed that inflammatory myopathies associated with anti-mitochondrial antibodies were frequently found in patients with the clinical features of a chronic disease course, muscle atrophy and cardiopulmonary involvement, and the characteristic histopathological feature of granulomatous inflammation. Our study suggests that inflammatory myopathies associated with anti-mitochondrial antibodies form a characteristic subgroup.