ウルリッヒ病

Muscle biopsy has long been regarded as the cornerstone for diagnosing pediatric muscular disorders; however, it is invasive and may be limited by sampling error and inconclusive histopathological findings. This study aimed to evaluate whether whole-exome sequencing (WES) can effectively replace muscle biopsy as a first-line diagnostic approach in children with suspected neuromuscular disorders. Between January 2018 and December 2025, we prospectively enrolled 47 pediatric patients presenting with clinical features suggestive of muscular disorders at a tertiary medical center in Taiwan. The cohort included patients with suspected muscular dystrophies (n = 21), congenital myopathies (n = 23), and multiplex ligation-dependent probe amplification (MLPA)-negative Duchenne muscular dystrophy (DMD; n = 3). All patients underwent WES as the initial diagnostic test without prior muscle biopsy. Trio-based analysis using parental samples was performed in 29.8% of cases. Variant interpretation followed the American College of Medical Genetics and Genomics (ACMG) guidelines. WES identified a definitive molecular diagnosis in 72.3% of patients (34/47). Diagnostic yields varied by subgroup: 100% (3/3) in MLPA-negative DMD, 71.4% (15/21) in muscular dystrophies, and 69.6% (16/23) in congenital myopathies. Pathogenic or likely pathogenic variants were detected in 31 distinct genes, including COL6A1 and COL6A3, which are associated with Ullrich congenital muscular dystrophy. Notably, 58.8% of diagnosed patients (20/34) received molecular diagnoses that differed from their initial clinical impression, encompassing conditions such as ZSWIM6-associated neurodevelopmental disorders, GJB2-related hearing loss, OCRL-associated Lowe syndrome, and various metabolic or syndromic disorders. In all three MLPA-negative DMD cases, WES identified point mutations amenable to mutation-specific therapies. No patient required a muscle biopsy for diagnostic confirmation during the study period. First-tier WES demonstrates high diagnostic utility in pediatric muscular disorders while avoiding invasive muscle biopsy. The high rate of diagnostic reclassification underscores the substantial phenotypic overlap between primary neuromuscular diseases and other neurological or systemic conditions. These findings support the early implementation of genetic testing to enable accurate diagnosis and timely initiation of targeted therapies.

Collagen VI-related myopathies (COL6-RM) encompass a spectrum of disorders characterized by muscle weakness, joint contractures, and connective tissue abnormalities resulting from mutations in the collagen VI genes. While muscle pathology has been extensively studied, tendon dysfunction has emerged as a critical yet underexplored contributor to disease severity, particularly in the development of joint contractures. Tendons from patients and animal models show disrupted collagen fibrillogenesis, altered extracellular matrix (ECM) composition, and impaired cellular mechanotransduction. Various defects in ECM remodeling pathways further exacerbate tendon pathology. Importantly, current clinical management remains limited to orthopedic interventions with modest outcomes, and targeted pharmacological strategies or gene-editing therapies are not yet available for clinical application. Therefore, understanding the basic pathogenic mechanisms underlying tendon dysfunction is essential for identifying novel therapeutic targets. This review provides a comprehensive synthesis of current understanding and recent advances concerning the role of mutated collagen VI in cellular and molecular mechanisms underlying tendon dysfunction. Emphasis is placed on the role of mutated collagen VI in the modulation of key signaling pathways related to mechanotransduction and primary cilium function in COL6-RM. By discussing these multifaceted contributions to disease pathogenesis, this review outlines future research directions in the field and highlights potential pathways for targeted therapeutic interventions.

AIM: Collagen VI has recently been strongly linked to poor outcomes in heart failure through increased endotrophin, a collagen VI-derived signaling molecule linked to fibrotic remodeling in cardiovascular disease. The mutation of collagen VI can result in Ullrich congenital muscular dystrophy and Bethlem myopathy, pointing to a critical function in muscle physiology. However, the functional role of collagen VI in the heart is poorly understood. In human heart failure with reduced ejection fraction, collagen VI is increased within the remodeled T-tubules, suggesting a possible role in tubular structure and Ca2+ dynamics. METHODS: To investigate this hypothesis, a global knockout of the collagen VI alpha 1 gene (Col6a1-/-) was generated in the rat. RESULTS: T-tubule structure and ryanodine receptor cluster organization were unchanged, but echocardiography demonstrated reduced systolic function. Consistent with this, isolated trabeculae from Col6a1-/- hearts generated significantly less peak stress, confirming impaired contractile force at the tissue level. Paradoxically, isolated cardiomyocytes from the Col6a1-/- rat had increased Ca2+ transient amplitude and increased sarcoplasmic reticulum Ca2+ load that would be expected to increase force. β-adrenergic stimulation further increased Ca2+ transient amplitude and was associated with diastolic Ca2+ release events in Col6a1-/- cardiomyocytes. Furthermore, β-adrenergic stimulation of Col6a1-/- trabeculae exhibited spontaneous contractions, indicating an increased susceptibility to arrhythmic activity. CONCLUSION: Together, these results indicate collagen VI has a role in both force transduction and Ca2+ cycling in the heart.

Collagen VI is an extracellular matrix component encoded by COL6A1, COL6A2 and COL6A3 genes. Causative variants in these genes are associated with the following collagen VI-related myopathies: severe Ullrich congenital muscular dystrophy (UCMD), milder Bethlem myopathy (BM) and intermediate phenotypes (INT). We report the mutation landscape of COL6A genes in 138 Italian patients affected with a collagen VI-related phenotype. The patient cohort included 44 (32%) UCMD, 9 (7%) INT, 61 (44%) BM and 21 (15%) INT/BM patients; 3 patients (2%) with a myosclerosis myopathy (MM) phenotype were also considered. We identified 104 different variants: 26 in COL6A1 (25%), 52 in COL6A2 (50%) and 26 in COL6A3 (25%). The variant spectrum includes missense, splicing, small indel, frameshifting and nonsense variants. Glycine substitutions in the triple helical domain of the collagen VI protein are the commonest variants and occur in all phenotypes. Our genetic profiling disclosed a unique mutation scenario and phenotypic association of the COL6A2 gene with respect to COL6A1 and COL6A3, which may be related to a different evolutive history. Landscape mutation analysis of variants occurring in ultrarare conditions, such as collagen VI-related myopathies, is crucial to better understand the variations' profile and to gain insight into fundamental knowledge about gene structure and its evolutive origin.

Induced pluripotent stem cells (iPSCs) have been used in research for the development of treatments for various intractable diseases due to their unlimited proliferative and multipotent potential. We are aiming to develop novel therapies for intractable muscular diseases using iPS cells by two approaches i.e. cell therapy and drug screening. In this presentation, I focus on the cell therapy research. We have developed a differentiation induction method that mimics the developmental stages and have succeeded in inducing skeletal muscle stem cells that are applicable to cell transplantation therapy. We have found that cell transplantation into Duchenne muscular dystrophy (DMD) model mice is effective in regenerating more than 10% of dystrophin-positive fibers. In addition, some of the cells have been engrafted as satellite cells in vivo, and it is expected that the therapeutic effect will continue for a long period of time. As for the efficacy to the motor function, we have recently revealed that the regeneration of dystrophin positive myofibers in DMD model mice mainly ameliorates muscle fatigue tolerance rather than maximal contraction force in vivo. We have also developed a differentiation method to induce mesenchymal stromal cells (MSCs) from iPSCs. Transplantation of iPSC-derived MSCs (iMSCs) into Ullrich congenital muscular dystrophy (UCMD) model mice enabled the restoration of collagen type VI which resulted in enhancement of muscle regeneration. Interestingly, somatic MSCs such as bone marrow-derived MSC or adipose-derived MSC do not have therapeutic effect even they can also restore collagen type VI by the transplantation. We have recently found one of the candidates which is responsible for the muscle regeneration and is specifically expressed in the iMSCs.