A Rare Association of Anti‐ SRP Antibody‐Positive Immune‐Mediated Necrotizing Myopathy and Sjögren Disease: Two Case Reports

INTRODUCTION/AIMS: Immune-mediated necrotizing myopathy (IMNM) is an autoimmune myositis which is characterized by severe muscle fiber necrosis and refractoriness to immunotherapies. Overlap between myositis and other autoimmune disorders is well-recognized; however, the coexistence of IMNM and Sjögren disease (SjD) is rare. We investigated the clinicopathological features of anti-signal recognition particle antibody-positive IMNM associated with SjD. METHODS: We retrospectively reviewed previously reported cases and analyzed the clinical and pathological features of two patients: a 68-year-old man with a 2-year history of sicca symptoms, who presented a 3-month history of dysphagia, difficulty arising from a sitting position and gait disturbance, and a 67-year-old woman with a 20-year history of sicca symptoms, who subsequently developed muscle weakness, dysphagia, and hyperCKemia. RESULTS: Muscle pathological findings in both patients were consistent with those of IMNM without SjD. In contrast, they exhibited relatively mild limb weakness and showed a better response to immunotherapies compared with patients with typical IMNM. Notably, Patient 1 developed severe Raynaud's phenomenon and digital ulcers, requiring additional treatment. DISCUSSION: IMNM associated with SjD may present with relatively mild muscle involvement compared with IMNM without SjD; however, SjD-related disease activity may become more prominent during the clinical course.