自发性炎症性肌病（IIM）成年患者中最近发现了能够识别特异性蛋白质4（Sp4）的自身抗体。抗Sp4自身抗体在抗TIF1自身抗体阳性的皮肌炎（DM）患者中同时存在，并且与较低癌症风险有关。本研究旨在调查青少年起病IIM患者中的抗Sp4自身抗体的患病率和临床特征。通过ELISA对横断面队列中的336名青少年肌炎患者和91名健康对照组进行筛选抗Sp4自身抗体。比较具有和没有抗Sp4自身抗体的患者的临床特征、预后和HLA等位基因。 23（7％）名青少年肌炎患者和没有一名对照组出现抗Sp4自身抗体。抗Sp4自身抗体在每个临床肌炎亚组中均发现。抗TIF1自身抗体阳性患者中抗Sp4自身抗体的阳性率显著更高（21［91％］对92［30％］，p＜0.001）。在抗TIF1自身抗体阳性亚组中，雷诺现象较常见（8 [38％]对2 [2％]，p＜0.001），并且抗Sp4自身抗体阳性患者的峰值AST显著较低。没有一名抗Sp4自身抗体阳性患者需要轮椅。在白种人患者中，DQA1*04和DRB1*08与抗Sp4自身抗体有关。抗Sp4自身抗体在青少年起病的IIM患者中发现，主要是与同时存在抗TIF1自身抗体的患者相关联。抗Sp4自身抗体阳性的患者代表一种表型亚组抗TIF1自身抗体阳性肌炎，其特点是雷诺现象较常见且不太明显的肌肉损伤，类似于这些自身抗体在成年人中的表现。在抗Sp4自身抗体阳性的青少年中识别了白种人IIM的新型免疫遗传风险因素。本文章受版权保护。版权所有。

Autoantibodies recognizing specificity protein 4 (Sp4) were recently discovered in adults with idiopathic inflammatory myopathies (IIM). Anti-Sp4 autoantibodies co-occurred in patients with anti-TIF1 autoantibody-positive dermatomyositis (DM) and were associated with a reduced risk of cancer. In the present study, the prevalence and clinical features associated with anti-Sp4 autoantibodies in juvenile-onset IIM were investigated.Sera from 336 patients with juvenile myositis in a cross-sectional cohort and 91 healthy controls were screened for anti-Sp4 autoantibodies by ELISA. Clinical characteristics, outcomes, and HLA alleles of those with and without anti-Sp4 autoantibodies were compared.Anti-Sp4 autoantibodies were present in 23 (7%) patients with juvenile myositis and none of the controls. Anti-Sp4 autoantibodies were found among each clinical myositis subgroup. The frequency of TIF1 autoantibody positivity was significantly higher among those with anti-Sp4 autoantibodies (21 [91%] vs 92 [30%], p<0.001). In the anti-TIF1 autoantibody-positive subgroup, Raynaud's phenomenon (8 [38%] vs 2 [2%], p<0.001) was more common and peak AST was significantly lower in those with anti-Sp4 autoantibodies. None of the patients with anti-Sp4 autoantibodies required a wheelchair. Among White patients, DQA1*04 and DRB1*08 were associated with anti-Sp4 autoantibodies.Anti-Sp4 autoantibodies were found in patients with juvenile-onset IIM, predominantly those with co-existing anti-TIF1 autoantibodies. Patients with anti-Sp4 autoantibodies represent a phenotypic subset of anti-TIF1 autoantibody-positive myositis characterized by frequent Raynaud's phenomenon and less pronounced muscle involvement, similar to adults with these autoantibodies. Novel immunogenetic risk factors for White patients with IIM were identified among juveniles with anti-Sp4 autoantibodies. This article is protected by copyright. All rights reserved.This article is protected by copyright. All rights reserved.