A 70-year-old female with a history of Sjogren’s syndrome and AQP4+NMOSD presented with a three-month history of progressive proximal upper and lower extremity weakness, dyspnea and dysphagia. She was diagnosed with AQP4+NMOSD two years prior after experiencing right optic neuritis. One year later, she had a few-week episode of severe intractable nausea leading to weight loss, but she did not have imaging to confirm area postrema syndrome. She was not on immunosuppressive treatment for AQP4+NMOSD attack prevention. Neurologic exam demonstrated appendicular and proximal greater than distal muscle weakness, hypoactive reflexes, and Trendelenburg gait pattern. Labs demonstrated CK
4550 U/L, and positive APQ-4 (1:10000), ANA (1:1280), SSA, SSB, and anti-smooth muscle antibodies. Testing for antibodies associated with autoimmune myopathy showed strongly positive anti-SRP (1:15360, normal <1:240), and negative anti-HMG-CoA reductase and Myomarker panel. EMG confirmed myopathy affecting proximal appendicular and axial musculature with features suggestive of necrosis, splitting or vacuolization of muscle fibers. Left triceps muscle biopsy demonstrated many regenerating and a few necrotic fibers, mild focal increase of endomysial fibrous connective tissue, and few mononuclear cells at perivascular sites, compatible with anti-SRP immune-mediated necrotizing myopathy. CT chest demonstrated interstitial lung disease. Pulmonary function test confirmed a restrictive pattern. Rituximab was selected to treat both anti-SRP necrotizing myopathy and AQP4+NMOSD.