Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA.
Muscle Nerve. 2021 Dec;64(6):734-739. doi: 10.1002/mus.27435. Epub 2021 Oct 15.
INTRODUCTION/AIMS: Immune-mediated necrotizing myopathy (IMNM) is an immune-mediated myopathy typically presenting with progressive subacute weakness and characteristic, but nonspecific, myopathological findings. Atypical cases however can mimic other inherited or acquired myopathies, depriving patients of treatment. We describe a cohort of such patients.
We retrospectively identified IMNM patients who either previously carried a diagnosis of an inherited myopathy established on clinicopathological grounds or whose muscle biopsies displayed atypical features suggestive of a different myopathy.
Among 131 IMNM patients, seven previously unreported patients (5%) met one of the above criteria. Three patients were diagnosed with limb-girdle muscular dystrophy on the basis of a chronic progressive course of weakness and family history of myopathy or cardiomyopathy. The other four patients displayed atypical histological features (two prominent mitochondrial abnormalities, one myofibrillar pathology, and one granulomatous inflammation). Immunostaining of biopsies from 12 additional IMNM patients did not identify myofibrillar pathology. The patient with granulomatous inflammation was known to have pulmonary sarcoidosis. Genetic testing for inherited myopathies was unrevealing. Antibodies against 3-hydroxy-3-methylglutaryl-CoA reductase or signal recognition particle were identified in 5 and 1 patients, respectively. Four patients presented with slowly progressive weakness over 3-13 y, while weakness was subacute over ≤6 mo in three patients. All patients responded to immunomodulatory therapy.
Atypical clinical and histological features can occur in IMNM patients, causing delays in diagnosis and treatment. Clinicians should, therefore, consider IMNM in the differential diagnosis of unexplained proximal myopathies in spite of atypical clinical and myopathological findings.
简介/目的：免疫介导的坏死性肌病（IMNM）是一种免疫介导的肌病，通常表现为进行性亚急性无力和特征性但非特异性的肌病理发现。然而，不典型病例可能模仿其他遗传性或获得性肌病，使患者错失治疗机会。我们描述了这样一组患者。
我们回顾性地确定了 IMNM 患者，这些患者之前根据临床病理依据诊断为遗传性肌病，或者其肌肉活检显示出不典型特征，提示为不同的肌病。
在 131 例 IMNM 患者中，有 7 例（5%）患者符合上述标准之一。3 例患者根据进行性无力的慢性进展过程和家族性肌病或心肌病病史诊断为肢带型肌营养不良症。其他 4 例患者显示出不典型的组织学特征（2 例突出的线粒体异常、1 例肌原纤维病理学和 1 例肉芽肿性炎症）。对 12 例额外的 IMNM 患者的活检进行免疫染色并未发现肌原纤维病理学。患有肉芽肿性炎症的患者已知患有肺结节病。遗传性肌病的基因检测结果无异常。分别在 5 例和 1 例患者中发现了针对 3-羟-3-甲基戊二酰辅酶 A 还原酶或信号识别颗粒的抗体。4 例患者的肌无力呈缓慢进行性，病程 3-13 年，3 例患者的肌无力呈亚急性，病程≤6 个月。所有患者均对免疫调节治疗有反应。
不典型的临床和组织学特征可发生在 IMNM 患者中，导致诊断和治疗延迟。因此，尽管存在不典型的临床和肌病理发现，临床医生也应在鉴别诊断不明原因的近端肌病时考虑到 IMNM。
