176 When Interstitial Lung Disease Represents the Major Clinical Feature in Antisynthetase Syndrome Cases which are Clearly Amyopathic, is it Justifiable to Still Regard Detected Antisynthetases as Myositis-Specific Antibodies?

Background: Antisynthetase syndrome (ASS) is usually characterized by the presence of myositis, a skin rash in DM cases, interstitial lung disease (ILD), RP, mechanic’s hands and non-erosive arthritis. ASS associates with the presence of antisynthetase antibodies, which target one of eight known amino-acyl-transfer RNA synthetases. Methods: We report three CTD cases presenting with ILD in association with an antisynthetase, but without detectable evidence of myositis. Results: Patient 1 is a 29-year-old female who presented with a 9 month history of dry cough and RP. Examination revealed ‘mechanic’s hands’ changes and bibasal end-inspiratory crackles, but without evidence of muscle weakness. Creatinine kinase (CK) levels were normal, as was muscle histology, but myositis serology by EuroImmune Line-Blot 4 testing demonstrated anti-PL-12 positivity. High-resolution CT (HRCT) confirmed the presence of ILD, and early immunosuppression was induced by i.v. CYC and prednisolone to target the respiratory disease. Patient 2 was a 60-year-old male who presented with increasing dyspnoea. He denied any generalized CTD symptoms. Examination revealed bibasal end-inspiratory crackles but no other CTD signs or clinically detectable muscle weakness. His CK at presentation and throughout was normal. HRCT showed a non-specific interstitial pneumonia (NSIP) pattern, but lung biopsy demonstrated an organising pneumonia. The ILD responded well to steroid treatment. Myositis serology by Line-Blot 4 ultimately confirmed anti-PL-12 positivity. Patient 3 was a 47-year-old male who presented with progressive dyspnoea. HRCT suggested an organising pneumonia, which was confirmed histologically. No general CTD features or underlying muscle weakness were ever detected. His CK was normal when tested, although by then he had received steroid treatment for some weeks. His ILD responded well to therapy. Routine serology confirmed anti-Jo-1 positivity.