Juvenile dermatomyositis (JDM) can be classified into clinical serological subgroups by distinct myositis-specific antibodies (MSAs). It is incompletely understood whether different MSAs are associated with distinct pathological characteristics, clinical disease activities, or response to treatment. We retrospectively reviewed clinicopathological data from consecutive JDM patients followed in the pediatric rheumatology clinic at a single center between October 2016 and November 2018. Demographics, clinical data, and laboratory data were collected and analyzed. Detailed muscle biopsy evaluation of four domains (inflammation, myofiber, vessels, and connective tissue) was performed, followed by statistical analysis. Of 43 subjects included in the study, 26 (60.5%) had a detectable MSA. The most common MSAs were anti-NXP-2 (13, 30.2%), anti-Mi-2 (7, 16.3%), and anti-MDA-5 (5, 11.6%). High titer anti-Mi-2 positively correlated with serum CK > 10,000 at initial visit (r = 0.96, p = 0.002). Muscle biopsied from subjects with high titer anti-Mi-2 had prominent perifascicular myofiber necrosis and perimysial connective tissue damage that resembled perifascicular necrotizing myopathy, but very little capillary C5b-9 deposition. Conversely, there was no positive correlation between the levels of the anti-NXP-2 titer and serum CK (r = − 0.21, p = 0.49). Muscle biopsies from patients with anti-NXP-2 showed prominent capillary C5b-9 deposition; but limited myofiber necrosis. Only one patient had anti-TIF1γ autoantibody, whose muscle pathology was similar as those with anti-NXP2. All patients with anti-MDA-5 had normal CK and near normal muscle histology. Muscle biopsy from JDM patients had MSA specific tissue injury patterns. These findings may help improve muscle biopsy diagnosis accuracy and inform personalized treatment of JDM.

中文翻译：

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少年皮肌炎自身抗体亚组的明显组织损伤模式。

少年皮肌炎（JDM）可以通过独特的肌炎特异性抗体（MSA）分为临床血清学亚组。尚不完全了解不同的MSA是否与不同的病理特征，临床疾病活动或对治疗的反应有关。我们回顾性研究了2016年10月至2018年11月在单个中心的儿科风湿病诊所随访的连续JDM患者的临床病理数据。收集并分析了人口统计学，临床数据和实验室数据。进行了四个区域（炎症，肌纤维，血管和结缔组织）的详细肌肉活检评估，然后进行统计分析。在研究中包括的43位受试者中，有26位（60.5％）的MSA可检出。最常见的MSA是抗NXP-2（13，30.2％），抗Mi-2（7，16.3％）和抗MDA-5（5，11.6％）。初诊时高滴度的抗Mi-2与血清CK> 10,000正相关（r = 0.96，p = 0.002）。从具有高滴度的抗Mi-2的受试者活检的肌肉具有明显的束周围肌纤维坏死和肌周围结缔组织损伤，类似于束周围坏死性肌病，但毛细血管C5b-9沉积很少。相反，抗NXP-2滴度与血清CK之间无正相关（r = − 0.21，p = 0.49）。抗NXP-2患者的肌肉活检显示出明显的毛细血管C5b-9沉积。但限制了肌纤维坏死。只有一名患者具有抗TIF1γ自身抗体，其肌肉病理与抗NXP2相似。所有抗MDA-5患者的CK均正常且肌肉组织学接近正常。JDM患者的肌肉活检具有MSA特定的组织损伤模式。这些发现可能有助于提高肌肉活检的诊断准确性，并有助于JDM的个性化治疗。