Case Presentation: A 51-year-old female with history of ESRD, Type II diabetes, and stroke with mild residual right lower and upper extremity weakness presented with left upper arm pain and swelling that had been present for several weeks and worsened to the point that she was no longer able to tolerate dialysis. The patient had undergone neurological evaluation on several occasions throughout the past year due to ongoing migratory extremity pain and intermittent episodes of focal extremity weakness, however work-up was consistently unremarkable, with no evidence of new stroke. She had been admitted one week prior to the current presentation for similar left arm pain, and one month prior for right arm pain. CT angiogram of her left upper extremity one week prior revealed no pathology. During the current admission, exam was notable for bilateral arm weakness, mild warmth and profound tenderness of the left arm, and right thenar atrophy. She had a tunneled dialysis catheter to her right internal jugular vein, and CT chest with superior vena cava protocol revealed no occlusions. MRI cervical spine did not reveal stenosis. On admission, lab work-up revealed an elevated ESR (120 mm/Hg), elevated CRP (233 mg/L), and CK (367 U/L). CK had been mildly elevated in past encounters as well. MRI of the bilateral humerus revealed edematous signal within multiple muscle groups suggestive of myositis. EMG of the left arm and leg revealed severe axonal sensorimotor polyneuropathy. Rheumatology work-up was undertaken for suspected myositis. Biopsy of the right arm and leg revealed atrophic changes, but no active myopathic damage or necrosis. Paradoxically, CK normalized days later and aldolase was not elevated, both findings that would be atypical for active inflammatory myositis. Myositis antibody panel was positive for anti-MI-2, which suggested an atypical presentation of dermatomyositis with burnt-out inflammatory disease.
Discussion: Inflammatory myositis typically presents with subacute symmetrical proximal muscle weakness. This patient’s case of dermatomyositis was atypical due to the lack of skin manifestations, involvement of both proximal and distal extremities, and presence of sensorimotor polyneuropathy. Furthermore, her comorbid conditions, which included ESRD with previous catheter access issues, diabetes with diabetic neuropathy, and stroke with residual deficits, may have masked and/or confounded symptoms that were due to an active inflammatory state. The factor that ultimately prompted the expanded neurological and rheumatologic evaluation leading to the diagnosis of inflammatory myositis was the exam finding of thenar atrophy. Thenar wasting can be seen in certain forms of inflammatory myositis, though tends to be a rare finding isolated to cases of very advanced, longstanding disease. This patient’s burnt-out disease likely could have been prevented with earlier diagnosis and initiation of immunosuppressive therapy.
Conclusions: Inflammatory myositis can present with a broad array of symptoms, and can be missed in patients with complex medical histories. Failure to promptly diagnose and initiate treatment for patients with inflammatory myositis can result in progression to muscle atrophy and burnt-out disease. As such, when approaching complaints of muscle pain and weakness, clinicians should include inflammatory myositis on the differential– especially when more common etiologies, in the context of each patient’s history, are ruled out.