Altered autophagy accompanied by abnormal autophagic (rimmed) vacuoles detectable by light and electron microscopy is a common denominator of many familial and sporadic non‐inflammatory muscle diseases. Even in the era of next generation sequencing (NGS), late‐onset vacuolar myopathies remain a diagnostic challenge. We identified 32 adult vacuolar myopathy patients from 30 unrelated families, studied their clinical, histopathological and ultrastructural characteristics and performed genetic testing in index patients and relatives using Sanger sequencing and NGS including whole exome sequencing (WES). We established a molecular genetic diagnosis in 17 patients. Pathogenic mutations were found in genes typically linked to vacuolar myopathy (GNE, LDB3/ZASP, MYOT, DES and GAA), but also in genes not regularly associated with severely altered autophagy (FKRP, DYSF, CAV3, COL6A2, GYG1 and TRIM32) and in the digenic facioscapulohumeral muscular dystrophy 2. Characteristic histopathological features including distinct patterns of myofibrillar disarray and evidence of exocytosis proved to be helpful to distinguish causes of vacuolar myopathies. Biopsy validated the pathogenicity of the novel mutations p.(Phe55*) and p.(Arg216*) in GYG1 and of the p.(Leu156Pro) TRIM32 mutation combined with compound heterozygous deletion of exon 2 of TRIM32 and expanded the phenotype of Ala93Thr‐caveolinopathy and of limb‐girdle muscular dystrophy 2i caused by FKRP mutation. In 15 patients no causal variants were detected by Sanger sequencing and NGS panel analysis. In 12 of these cases, WES was performed, but did not yield any definite mutation or likely candidate gene. In one of these patients with a family history of muscle weakness, the vacuolar myopathy was eventually linked to chloroquine therapy. Our study illustrates the wide phenotypic and genotypic heterogeneity of vacuolar myopathies and validates the role of histopathology in assessing the pathogenicity of novel mutations detected by NGS. In a sizable portion of vacuolar myopathy cases, it remains to be shown whether the cause is hereditary or degenerative.

中文翻译：

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NGS时代空泡性肌病的鉴别诊断。

改变的自噬伴随着可通过光学和电子显微镜检测到的异常自噬（边缘）空泡是许多家族性和散发性非炎症性肌肉疾病的共同特征。即使在下一代测序 (NGS) 时代，迟发性空泡肌病仍然是诊断方面的挑战。我们确定了来自 30 个无关家族的 32 名成人空泡性肌病患者，研究了他们的临床、组织病理学和超微结构特征，并使用 Sanger 测序和 NGS 包括全外显子组测序 (WES) 对索引患者和亲属进行了基因检测。我们在 17 名患者中建立了分子遗传学诊断。在通常与空泡性肌病相关的基因（GNE、LDB3 /ZASP、MYOT、DES 和 GAA），但也存在与严重改变的自噬（FKRP、DYSF、CAV3、COL6A2、GYG1 和 TRIM32）和双基因面肩肱型肌营养不良症不经常相关的基因中2. 特征性组织病理学特征，包括不同的肌原纤维模式混乱和胞吐作用的证据证明有助于区分空泡性肌病的原因。活检验证了新的突变p的致病性。（Phe55 *）和p（Arg216 *）GYG1和p的。（Leu156Pro）TRIM32突变与外显子2的化合物杂合缺失组合TRIM32和扩展的表型Ala93Thr-小窝病和肢带型肌营养不良症 2iFKRP突变。在 15 名患者中，Sanger 测序和 NGS panel 分析未检测到因果变异。在其中 12 例中，进行了 WES，但没有产生任何明确的突变或可能的候选基因。在其中一名有肌肉无力家族史的患者中，空泡性肌病最终与氯喹治疗有关。我们的研究说明了液泡性肌病的广泛表型和基因型异质性，并验证了组织病理学在评估 NGS 检测到的新突变的致病性方面的作用。在相当大一部分空泡性肌病病例中，病因是遗传性还是退行性仍有待证明。