遠位型ミオパチー

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare disease characterized by inflammation of small and medium-sized blood vessels, leading to damage in various organs. It is classically associated with asthma, eosinophilia, and multisystem involvement, including frequent peripheral nervous system manifestations. We report the case of a 72-year-old woman with a history of asthma, rhinitis, and strokes, who presented with progressive muscle weakness, myalgia, and distal sensory deficits. Neurological examination revealed proximal muscle weakness and a length-dependent sensory loss. Laboratory investigations demonstrated marked eosinophilia, elevated creatine kinase, and positive antimyeloperoxidase antibodies with an atypical cytoplasmic ANCA pattern. Imaging showed diffuse muscular hypermetabolism on positron emission tomography, while electromyography and nerve conduction studies revealed a length-dependent axonal polyneuropathy with mild myopathic features. Muscle biopsy demonstrated mild nonspecific myopathic changes without definite evidence of vasculitis or eosinophilic infiltrates. Based on the 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria, a diagnosis of EGPA with neurological involvement was established. The patient was treated with high-dose corticosteroids and rituximab, resulting in significant clinical and biochemical improvement at 3 months. This case illustrates the coexistence of atypical neurological manifestations of EGPA, including prominent myopathy, length-dependent polyneuropathy, and retrospectively suspected central nervous system vasculitic involvement, emphasizing the importance of early recognition and multidisciplinary management.

BACKGROUND: Pain is a common and burdensome symptom in patients with idiopathic inflammatory myopathies (IIM). Our aim was to identify pain phenotypes in IIM that may reflect distinct underlying mechanisms. METHODS: An anonymous electronic survey of patients with self-reported IIM and pain attributable to myositis was circulated. The survey included questions related to demographics, IIM-related information, pain characteristics and the Fibromyalgia Survey Questionnaire. Latent class analysis (LCA) was performed using four variables including distribution, pattern, difference in pain during myositis flare vs now, and disease duration. Class validity was assessed using pain characteristics, fibromyalgia criteria fulfilment and symptom burden. RESULTS: A total of 426 participants were included. LCA identified four classes: i) class 1 with proximal arm- and leg-predominant pain and lowest persistent pain, ii) class 2 with diffuse axial and proximal limb-predominant pain, iii) class 3 with diffuse axial and distal-leg predominant pain and iv) class 4 with widespread axial and extremity pain and the highest persistent pain. In post-hoc analyses, class 1 primarily included participants with earlier IIM and a lower rate of fibromyalgia. Class 2 and 3 included participants with intermediate fibromyalgia symptom burden while class 4 included participants with the highest pain intensity and fibromyalgia. CONCLUSION: In this large international cohort of patients with self-reported IIM and pain, we identified four different pain phenotypes. These phenotypes range from a localized disease-related nociceptive pattern to a widespread fibromyalgia-like nociplastic pattern. Our findings highlight the heterogeneity of myositis-related pain and may inform future mechanistic studies and phenotype-directed management strategies.

A 56-year-old man with a family history of myopathy developed generalized muscle weakness at age 45. At age 52, he was diagnosed with inclusion-body myopathy with Paget disease of bone and frontotemporal dementia (IBMPFD), confirmed by muscle pathology and a pathogenic VCP mutation (c.464G>A, p.R155H). Concurrent testing identified a heterozygous SCN4A variant (c.215C>T, p.P72L), a known modifier in myotonic dystrophy type 2 (DM2). At age 56, neurological examination showed proximal muscle weakness (MMT grade 3), distal lower extremity weakness (grade 4-5), and areflexia. He ambulated independently with knee locking, though squatting was impossible. No myotonia or periodic paralysis was observed. Multimodal imaging captured classic IBMPFD hallmarks: skeletal muscle computed tomography (CT) showed advanced fatty degeneration of paraspinal and limb muscles; brain magnetic resonance imaging (MRI) revealed mild frontal lobe atrophy; and bone scintigraphy showed increased uptake in the lumbar spine and iliums. Although the SCN4A p.P72L variant exacerbates DM2, the patient's three-year progression from independent walking to cane use remained consistent with the natural history of IBMPFD. This case suggests that in the presence of a robustly penetrant VCP phenotype, the SCN4A variant does not necessarily exert a clinical modifying effect.

INTRODUCTION: GNE myopathy is a rare autosomal recessive distal myopathy classically characterized by symmetrical distal muscle weakness with relative quadriceps sparing. However, phenotypic variability, including asymmetric onset, may obscure the diagnosis and mimic neuropathic disorders. CASE PRESENTATION: A 27-year-old Bangladeshi man presented with a 2-year history of progressive distal weakness, initially involving the left lower limb and later affecting the contralateral limb and distal upper extremities. Neurological examination revealed asymmetric distal weakness with bilateral foot drop and preserved sensory function. Serum creatine kinase was moderately elevated (892 U/L). Nerve conduction studies showed preserved sensory responses with reduced motor amplitudes, while electromyography demonstrated a distal-predominant myopathic pattern. Magnetic resonance imaging of the spine was unremarkable. Clinical exome sequencing identified a homozygous likely pathogenic variant in the GNE gene NM_005476.7:c.484C>T (p.Arg162Cys), confirming the diagnosis. CONCLUSION: This case highlights an asymmetric presentation of GNE myopathy mimicking peripheral neuropathy. Recognition of such phenotypic variability and integration of clinical, electrophysiological, and genetic findings are crucial for accurate diagnosis and to avoid misclassification as a neuropathic disorder.