Three cases of interstitial pneumonia with anti-signal recognition particle antibody
Anti-signal recognition particle antibody (SRP-Ab) is a myositisspecific 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
... 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 Fig. 1. Chest radiograph on admission. Case 1 (a, b): Consolidation was observed in the bilateral dorsal lower lung fields. Case 2 (c): Reticular shadows were observed in the bilateral dorsal lung bases. Case 3 (d): Ground-glass opacities were observed in the bilateral lung bases. Peer review under responsibility of Japanese Society of Allergology.