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

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.

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.

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.

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.