Anti-OJ antibody-positive anti-synthetase syndrome associated with hepatocellular carcinoma.

Anti-synthetase syndrome (ASS), a rare autoimmune disorder, is characterised by antibodies against aminoacyl-tRNA synthetases. Anti-OJ antibodies are particularly rare and often underdiagnosed because conventional assays may yield false-negative results. We report a case of a man in his 70s with hepatocellular carcinoma (HCC) who presented with progressive proximal muscle weakness and dropped head syndrome. Investigations revealed elevated creatine kinase levels, abnormal muscle imaging findings and myopathic changes. Conventional serology was negative, but wheat germ cell-free protein synthesis-based assay (A-cube) confirmed anti-OJ positivity. Muscle biopsy revealed necrotic and regenerating fibres without perifascicular necrosis. Following hepatic lobectomy, muscle weakness and laboratory abnormalities improved without postoperative immunotherapy. This is the second reported case of anti-OJ-positive ASS associated with HCC. Both patients improved after tumour resection without immunosuppressive therapy. This case highlights the diagnostic value of advanced serological testing and suggests that treating underlying malignancy may contribute to paraneoplastic anti-OJ-positive ASS remission.