The Myocardial Accumulation of Aggregated Desmin Protein in a Case of Desminopathy with a de novo DES p.R406W Mutation.

Desminopathy is a cardiac and skeletal myopathy caused by disease-causing variants in the desmin (DES) gene and represents a subgroup of myofibrillar myopathies, where cytoplasmic desmin-postive immunoreactivity is the pathological hallmark. We herein report a 28-year-old Japanese man who was initially diagnosed with sporadic hypertrophic cardiomyopathy with atrioventricular block at 9 years old and developed weakness in the soft palate and extremities. The myocardial tissue dissected during implantation of the ventricular-assisted device showed a dilated phase of hypertrophic cardiomyopathy and intracellular accumulation of proteinase K-resistant desmin aggregates. Genetic testing confirmed a de novo mutation of DES, which has already been linked to desminopathy. As the molecular diagnosis of desminopathy is challenging, particularly if patients show predominantly cardiac signs and a routine skeletal muscle biopsy is unavailable, these characteristic pathological findings of endomyocardial proteinase K-resistant desmin aggregates might aid in clinical practice.

Expanded clinical spectrum of oculopharyngodistal myopathy type 1.

INTRODUCTION/AIMS: Heterozygous CGG repeat expansions in low-density lipoprotein receptor-related protein 12 (LRP12) have recently been identified as a cause of oculopharyngodistal myopathy (OPDM), and the disease is designated as OPDM type 1 (OPDM1). In contrast to broadening of our knowledge on the genetic background of OPDM, what we know of the clinical phenotype of genetically confirmed OPDM1 remains limited. METHODS: This investigation was a single-center case series study of OPDM consisting of ten patients from seven families. Repeat-primed polymerase chain reaction and Southern blot analyses were performed to confirm the CGG repeat expansions in LRP12. Clinical findings were retrospectively reviewed. RESULTS: Seven patients from five families were identified as having CGG repeat expansions in LRP12. We found a high prevalence of axial muscle involvement, such as neck muscle weakness (6/7) and fatty infiltration in the rectus abdominis muscle, as revealed by computed tomography (5/5). We identified patients with very subtle oculopharyngeal symptoms, mimicking isolated distal myopathy. Muscle specimens were collected from the biceps brachii and tibialis anterior muscles of three patients. Myopathic changes were more severe with more atrophic fibers forming clusters in the tibialis anterior than the biceps brachii muscles of these three patients. No rimmed vacuoles were observed in the biceps brachii muscles in two of the three patients. DISCUSSION: This study shows the expanded clinical spectrum of OPDM1, highlighting the importance of axial muscle evaluation in OPDM1. Considering patients with very subtle oculopharyngeal symptoms, genetic analysis of LRP12 should be considered in patients with isolated distal myopathy.

DMD exon 2 duplication due to a complex genomic rearrangement is associated with a somatic mosaicism.

We report the case of a patient with dystrophinopathy caused by DMD exon 2 duplication, showing marked asymmetric muscle atrophy. Immunostaining of the biopsied muscle tissue showed a mosaic staining, suggesting a somatic mosaicism. Polymerase chain reaction (PCR) analysis showed only one breakpoint, and long-read whole-genome sequencing revealed the entire structure of the rearranged sequence. The complex rearrangement was composed of two tandem duplications: one showed a microhomology near the breakpoint, suggesting a microhomology-mediated mechanism, whereas the other was associated with flanking short tandem repeats. The long-read sequencing also suggested the presence of a wild-type nonduplicated sequence, supporting somatic mosaicism. Whereas complementary DNA and western blot analyses were not useful, droplet digital PCR (ddPCR) analysis showed an average copy number of 1.61, enabling accurate estimation of the proportion of cells containing the duplication. Long-read sequencing and ddPCR analysis were useful for revealing the rearrangements and the precise copy number.

Alanine transaminase is predominantly increased in the active phase of anti-HMGCR myopathy.

Autoantibodies against 3­hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and the signal recognition particle (SRP) are representative antibodies causing immune-mediated necrotizing myopathies (IMNM), called as anti-HMGCR and anti-SRP myopathies, respectively. Here, we analyzed the differences in routine blood test results between 56 anti-HMGCR and 77 anti-SRP myopathy patients. A higher alanine transaminase (ALT) level and a lower aspartate transaminase (AST)/ALT ratio were observed in anti-HMGCR myopathy patients [ALT, 265.7 ±â€¯213.3 U/L (mean ± standard deviation); AST/ALT ratio, 0.88 ±â€¯0.32] than in anti-SRP-myopathy patients (ALT, 179.3 ±â€¯111.2 U/L, p < 0.05; AST/ALT ratio, 1.28 ±â€¯0.40, p < 0.01). In the active phase, anti-HMGCR myopathy often showed ALT predominance, whereas anti-SRP myopathy often showed AST predominance. In addition, there were differences in erythrocyte sedimentation rate (ESR), total cholesterol (TChol) level, and high-density lipoprotein (HDL) level between anti-HMGCR and anti-SRP myopathies (ESR: HMGCR, 24.4 ±â€¯20.8 mm/1 h; SRP, 35.7 ±â€¯26.7 mm/1 h, p = 0.0334; TChol: HMGCR, 226.7 ±â€¯36.6 mg/dL; SRP, 207.6 ±â€¯40.8 mg/dL, p = 0.0163; HDL: HMGCR, 58.4 ±â€¯13.9 mg/dL; SRP, 46.2 ±â€¯17.3 mg/dL, p < 0.01). Additional studies on the differences in routine blood test results may further reveal the pathomechanisms of IMNM.

Pembrolizumab on pre-existing inclusion body myositis: a case report.

BACKGROUND: Cases of exacerbation of pre-existing neuromuscular diseases induced by immune checkpoint inhibitors (ICIs) have rarely been reported because patients with autoimmune diseases have generally been excluded from ICI therapy due to the increased risk of exacerbation. We describe the first case of an elderly patient who experienced exacerbation of a previously undiagnosed sporadic inclusion body myositis (sIBM), the most common myopathy in the geriatric population, which was triggered by anti-programmed cell death-1 therapy. CASE PRESENTATION: A 75-year-old man who was receiving pembrolizumab presented with limb weakness. Three years prior, he had noticed slowly progressive limb weakness, but he received no diagnosis. After the first infusion of pembrolizumab, his creatine kinase (CK) levels had increased. The neurological examination and muscle biopsy findings confirmed the diagnosis of sIBM and suggested exacerbation of sIBM induced by pembrolizumab. After the patient's CK levels decreased, pembrolizumab was restarted. The tumor progressed after its treatment with pembrolizumab. The patient died after 15 months of follow-up. CONCLUSIONS: In patients with slowly progressive limb weakness, sIBM should be explored before ICI therapy. In addition, if patients show high CK levels after ICI introduction, it is necessary to confirm whether they have sIBM in order to avoid unnecessary immunosuppressive therapies and assess whether they can tolerate ICI reintroduction.

Inflammatory myopathy with myasthenia gravis: Thymoma association and polymyositis pathology.

Objective: To provide evidence that idiopathic inflammatory myopathy (IM) with myasthenia gravis (MG) frequently shows thymoma association and polymyositis (PM) pathology and shares clinicopathologic characteristics with IM induced by immune checkpoint inhibitors (ICIs). Methods: We analyzed the clinicopathologic features of 10 patients with idiopathic IM and MG identified in 970 consecutive patients with biopsy-proven IM. Results: Seven patients (70%) had thymoma. IM and MG were diagnosed with more than 5-year time difference in 6 thymomatous patients and within 1 year in 1 thymomatous and 3 nonthymomatous patients. Seven thymomatous patients showed rhabdomyolysis-like features with respiratory failure (4/7), dropped head (3/7), cardiac involvement (2/7), and positive anti-acetylcholine receptor (anti-AChR) and anti-titin antibodies (7/7 and 4/6, respectively) but rarely showed ocular symptoms (2/7) or decremental repetitive nerve stimulation (RNS) responses (1/7) at IM diagnosis. Three nonthymomatous patients showed acute cardiorespiratory failure with rhabdomyolysis-like features (1/3), positive anti-AChR and anti-titin antibodies (3/2 and 2/2, respectively), and fluctuating weakness of the skeletal muscle without ocular symptoms (3/3). Muscle pathology showed a PM pathology with infiltration of CD8-positive CD45RA-negative T-lymphocytes (9/9), scattered endomysial programmed cell death 1 (PD-1)-positive cells (9/9), and overexpression of programmed cell death ligand 1 (PD-L1) on the sarcolemma of muscle fibers around the infiltrating PD-1-positive cells (7/9). Conclusion: Rhabdomyolysis-like features, positive anti-AChR antibody without decremental RNS responses, and PD-L1 overexpression are possible characteristics shared by ICI-induced IM. Frequent thymoma association in patients with idiopathic IM and MG may suggest thymoma-related immunopathogenic mechanisms, including dysregulation of the immune checkpoint pathway.