Anti-signal recognition particle antibody (SRP-Ab) is a myositis-specific antibody (MSA) that is found in serum of patients with myositis characterized by a necrotizing myopathy. Because patients with SRP-Abs have few extra-muscular manifestations,1 the clinical characteristics of interstitial pneumonia (IP) with SRP-Ab have not been clarified. Here, we present three cases of IP with SRP-Ab. Case 1: A 51-year-old man with a one-year history of cough and sputum was referred to our hospital for gradual progression of his symptoms. On admission, he did not have muscle pain or proximal muscle weakness. CK was markedly elevated (1160 U/L), and aldolase (16.2 U/L), KL-6 (1529 U/mL) and SP-D (312.4 ng/mL) were also elevated. Auto-immune antibodies analyzed were negative. Pulmonary function tests revealed restrictive respiratory dysfunction. His CT showed consolidation in the bilateral lower lungs (Fig. 1a, b). Bronchoalveolar lavage revealed an increase in lymphocytes. He was diagnosed as having IP associated with polymyositis (PM). Although the patient was suspected to have myositis, there was no evidence of myopathy after careful examination by MRI and electromyography. Monthly cyclophosphamide pulse therapy was started. Although CK, aldolase, and fibrotic markers were temporally normalized, they gradually increased. After six times of cyclophosphamide therapy, oral prednisolone was started. As a result, muscle enzymes and fibrotic parameters were decreased to normal levels. His chest radiograph findings were gradually improved with significant increase in forced vital capacity (FVC) at 46 months after prednisolone. Positive SRP-Ab was confirmed by RNA immunoprecipitation (RIP) assay. Case 2: A 63-year-old man with an 8-year history of myositis was referred to our hospital for cough and dyspnea on exertion. He had complained of progressive lower extremity weakness and had been treated with oral prednisolone and cyclophosphamide for five years. Although muscle strength had been improved, he developed respiratory symptoms. On admission, he did not have muscle weakness and cutaneous rash. His CT revealed reticulation in the bilateral lungs (Fig. 1c). CK (328 U/L), KL-6 (1128 U/mL) and SP-D (361.2 ng/mL) were elevated. Auto-immune antibodies analyzed were negative. Pulmonary function tests were within normal range except a low diffusion capacity. Bronchoalveolar lavage revealed a slight increase in eosinophils. He was diagnosed as having IP associated with PM, and oral prednisolone and cyclophosphamide were continued. However, due to the worsening of the patient's dyspnea as well as development of numbness of the hands and fingers with tapering prednisolone, intravenous immunoglobulin therapy was conducted. After improvement of his symptoms, his chest radiological findings had not been worsened with oral prednisolone and immunosuppressants. Afterward, although he experienced acute exacerbation of IP twice, his radiological findings and symptoms were significantly improved after steroid pulse therapies. Positive SRP-Ab was confirmed by RIP assay. Case 3: A 54-year-old man with a 6-month history of progressive upper and lower extremity weakness was referred to our hospital. He presented with a dropped head and his muscle strength grade was 2/5 in the extremities on admission. CK (554 U/L) and aldolase (60.2 U/L) were markedly elevated. His MRI showed profound muscle edema (Fig. 2a–c), and myopathic changes were found on electromyography. A left deltoid muscle biopsy demonstrated degeneration and regeneration muscle fibers (Fig. 2d, e). His CT revealed ground-glass opacities in the bilateral lungs (Fig. 1d) and SP-D (182.6 ng/mL) was elevated. Auto-immune antibodies analyzed were negative. The patient was diagnosed as having inflammatory myopathy with IP, and oral prednisolone was started. His muscle strength was gradually improved, and CK decreased to the normal level. However, CK was elevated with tapering prednisolone and his muscle strength became impaired again. On the other hand, no significant worsening in his CT findings was observed during follow-up. Positive SRP-Ab was confirmed by RIP assay. Anti-ARS antibody (ARS-Ab) was not detected in all cases.
展开▼
机译：抗信号识别颗粒抗体（SRP-Ab）是肌炎特异性抗体（MSA），存在于以坏死性肌病为特征的肌炎患者血清中。由于患有SRP-Ab的患者很少有肌肉外表现1，因此尚不清楚具有SRP-Ab的间质性肺炎（IP）的临床特征。在这里，我们介绍了三种带有SRP-Ab的IP案例。病例1：一名咳嗽和痰史为一年的51岁男子因其症状逐渐进展而被转诊至我院。入院时，他没有肌肉疼痛或近端肌肉无力。 CK显着升高（1160 U / L），醛缩酶（16.2 U / L），KL-6（1529 U / mL）和SP-D（312.4 ng / mL）也升高。分析的自身免疫抗体为阴性。肺功能检查发现限制性呼吸功能不全。他的CT显示在双侧下肺部巩固（图1a，b）。支气管肺泡灌洗显示淋巴细胞增加。他被诊断患有IP与多发性肌炎（PM）相关。尽管怀疑患者患有肌炎，但经MRI和肌电图仔细检查后，没有肌病的迹象。开始每月进行环磷酰胺脉冲治疗。尽管CK，醛缩酶和纤维化标志物在时间上已正常化，但它们逐渐增加。经过六次环磷酰胺治疗后，开始口服泼尼松龙。结果，肌肉酶和纤维化参数降低到正常水平。泼尼松龙后46个月，他的胸部X光片检查结果逐渐改善，同时显着增加了强制肺活量（FVC）。 RNA免疫沉淀（RIP）分析证实SRP-Ab阳性。病例2：一名63岁的男性，有8年的肌炎史，因劳累咳嗽和呼吸困难被转诊到我院。他抱怨下肢进行性无力，并已接受口服泼尼松龙和环磷酰胺治疗五年。尽管肌肉力量得到了改善，但他出现了呼吸道症状。入院时，他没有肌肉无力和皮疹。他的CT显示双侧肺有网状结构（图1c）。 CK（328 U / L），KL-6（1128 U / mL）和SP-D（361.2 ng / mL）升高。分析的自身免疫抗体为阴性。除低扩散能力外，肺功能测试均在正常范围内。支气管肺泡灌洗显示嗜酸性粒细胞略有增加。他被诊断患有IP与PM相关，并且继续口服泼尼松龙和环磷酰胺。但是，由于患者的呼吸困难加重，强的松龙逐渐变窄，导致手和手指麻木，因此进行了静脉免疫球蛋白治疗。症状改善后，口服泼尼松龙和免疫抑制剂未使胸部放射学检查结果恶化。此后，尽管他两次经历了IP的急性加重，但在接受类固醇脉冲疗法后，其放射学发现和症状得到了明显改善。 RIP分析证实SRP-Ab阳性。病例3：一名54岁的男子，其进行性上下肢无力病史为6个月，已转诊至我院。他低着头，入院时四肢肌肉力量等级为2/5。 CK（554 U / L）和醛缩酶（60.2 U / L）明显升高。他的MRI显示出严重的肌肉水肿（图2a–c），并在肌电图检查中发现了肌病性改变。左三角肌活检显示变性和再生肌纤维（图2d，e）。他的CT显示双侧肺毛玻璃样混浊（图1d），SP-D（182.6 ng / mL）升高。分析的自身免疫抗体为阴性。该患者被诊断患有IP炎性肌病，并开始口服泼尼松龙。他的肌肉强度逐渐提高，而CK降低到正常水平。然而，CK随着逐渐增加的泼尼松龙的升高而升高，他的肌肉力量再次受损。另一方面，在随访期间未观察到他的CT表现明显恶化。 RIP分析证实SRP-Ab阳性。在所有情况下均未检测到抗ARS抗体（ARS-Ab）。
展开▼
