Rare Case of Immune-Mediated Necrotizing Myopathy With Isolated Dysphagia as Presenting Symptom

ABSTRACT

Introduction: Immune mediated necrotizing myopathy (IMNM) is a rare, but progressive disease that accounts for about 19% of all inflammatory myopathies. Dysphagia occurs in 20-30% of IMNM patients. It often follows proximal muscle weakness and ensues in the later stages of the disease. We report a rare case of IMNM, presenting with dysphagia as the initial symptom, followed by proximal muscle weakness. Case Description/Methods: A 74-year-old male with a past medical history of coronary artery disease, hypertension, and hyperlipidemia presented to the ED with 2-3 weeks of intractable nausea, vomiting, and dysphagia for solids and liquids. Vital signs were stable, and initial labs displayed an AST of 188 U/L and ALT of 64 U/L with a normal bilirubin. Computed tomogram of the chest, abdomen, and pelvis were negative. An esophagram showed moderate to severe tertiary contraction, no mass or stricture, and a 13 mm barium tablet passed without difficulty. Esophagogastroduodenoscopy exhibited a spastic lower esophageal sphincter. Botox injections provided no significant relief. He then developed symmetrical proximal motor weakness and repeat labs demonstrated an elevated creatine kinase (CK) level of 6,357 U/L and aldolase of 43.4 U/L. Serology revealed positive PL-7 autoxantibodies, but negative JO-1, PL-12, KU, MI-2, EJ, SRP, anti-smooth muscle, and anti-mitochondrial antibodies. Muscle biopsy did not unveil endomysial inflammation or MHC-1 sarcolemmal upregulation. The diagnosis of IMNM was suspected. A percutaneous endoscopic gastrostomy feeding tube was placed as a mean of an alternative route of nutrition. He was started on steroids and recommended to follow up with outpatient rheumatology. He expired a month later after complications from an unrelated COVID-19 infection. Discussion(s) The typical presentation of IMNM includes painful proximal muscle weakness, elevated CK, presence of myositis-associated autoantibodies, and necrotic muscle fibers without mononuclear cell infiltrates on histology. Dysphagia occurs due to immune-mediated inflammation occurring in the skeletal muscle of the esophagus, resulting in incoordination of swallowing. Immunotherapy and intravenous immunoglobulin are often the mainstay of treatment. Our patient was unique in presentation with dysphagia as an initial presenting symptom of IMNM, as well as elevated enzymes from muscle breakdown. It is critical as clinicians to have a high degree of suspicion for IMNM due to the aggressive nature of the disease and refractoriness to treatment.