Dysphagia During Pharyngeal and Esophageal Phase of Seronegative Immune-Mediated Necrotizing Myopathy: A Case Report

Immune-mediated necrotizing myopathy (IMNM) is a category of inflammatory muscle diseases that was identified as distinct from polymyositis. The majority of IMNM cases involve the presence of myositis-specific autoantibodies, specifically anti-signal recognition particle (anti-SRP) or anti-3-hydroxy-3-methylglutaryl-coA reductase (anti-HMGCR). However, some IMNM patients do not exhibit these antibodies, which is referred to as seronegative status. Swallowing difficulties are a common symptom in muscle diseases, including IMNM. However, there is a lack of research specifically investigating the swallowing disorder profile in patients with antibody-negative IMNM. We describe an 88-year-old Japanese woman case of seronegative IMNM with dysphagia. She developed pain and muscle weakness in the right shoulder followed by muscle weakness in the bilateral shoulder muscles and lower limbs. One year after initial onset, head ptosis and dysphagia developed and she visited our hospital. Based on muscle biopsy and blood tests, she was diagnosed with IMNM. At age 90, she was admitted to our hospital for treatment and received immunotherapy including intravenous methylprednisolone, oral prednisolone, methotrexate and intravenous immunoglobulin therapy. A swallowing screening test immediately after admission revealed coughing during water drinking, but this improved with thickened fluids. The patient continued to experience choking during meals, prompting a videofluoroscopic swallowing study (VF). VF showed decreased clearance of food residue during the pharyngeal phase and retention and reflux during the esophageal phase. Despite immunotherapy, the patient did not experience any significant improvement in clinical symptoms, including limb strength or dysphagia. This case report highlights dysphagia in a seronegative IMNM patient, demonstrating food retention and reflux in the lower esophagus and decreased pharyngeal clearance on VF. This suggests potential esophageal smooth muscle damage due to an autoimmune mechanism. Further research on dysphagia in IMNM, particularly in the seronegative type, is crucial to understand the pathogenesis and develop effective treatment strategies.