Abstract | November 9, 2021
Refractory Rhabdomyolysis: A Rare NAMe to Remember
- Recognize the differential diagnosis and workup of persistently elevated CPK;
- Understand the diagnosis of necrotizing autoimmune myositis.
Introduction: Myositis is a common medical diagnosis in the inpatient setting. We present a unique case/work up with an unclear etiology to this diagnosis.
Case presentation: A 68-year old female with a past medical history of CAD, diabetes mellitus, HTN, hyperlipidemia, CVA, and G tube presented with worsening generalized weakness for the past few days. The patient also reported that her G tube was malfunctioning. Physical exam: HR 98, BP 115/77, RR 16; showed an obese female in no acute distress. Heart: RRR no MRG; Lungs: clear; Abdomen: soft, nontender to palpation; Neurologic: 1/5 muscle strength in the LUE and LLE, 2/5 muscle strength in the RUE and RLE. Labs: CPK 8478, troponin 226, alkaline phosphatase 241, ALT 213, AST 391. Hospital course: G tube was replaced and patient was treated for MRSA infection located at the G tube site; CPK trended up to 15,000. Suspecting myositis, a muscle biopsy was performed of the vastus lateralis muscle and pathology showed numerous necrotic and regenerating fibers suggestive of necrotizing autoimmune myopathy. EMG and NCS also showed axonal peripheral neuropathy. The patient was placed on prednisone 40mg daily after an initial loading dose of 125 mg resulting in resolution of the elevated CPK before discharge.
Final Diagnosis: Necrotizing autoimmune myopathy (NAM) is a rare subgroup of myopathies that is a branch off of a group of diseases called idiopathic inflammatory myopathies (IIM). NAM is characterized by progressive proximal muscle weakness and findings of necrotic muscle fibers with absent or minimal inflammation on muscle biopsy. IVIG, plasmapheresis, immunosuppressive therapy, and high dose corticosteroids have been associated with strength improvement and favorable outcome.
Management: NAM is a rare disorder of musculature that is associated with statin use, autoimmune disease, and malignancy. Timely muscle biopsy and early aggressive treatment have been associated with improved outcomes.