Inflammatory myopathies Quiz: Ace Your Exams

A 50-year-old woman presents to the clinic for evaluation of a two-month history of worsening shortness of breath. Additionally over the past two months, she has experienced intermittent low-grade fevers, diffuse muscle weakness and pain, and swelling of the joints of her hands. She has no dysphagia or changes in the color of her fingers with exposure to cold. She has a history of diabetes mellitus and hypertension for which she takes metformin and carvedilol, respectively. Temperature is 37.8ºC (100.0ºF), pulse is 84/min, respiratory rate is 18/min, blood pressure is 131/85 mmHg, and SpO₂ is 94% on room air. Lung auscultation reveals bilateral basilar inspiratory crackles. Examination of the hands shows bilateral hyperkeratosis, fissures, and scaling on the radial aspect of the fingers along with swelling of the bilateral metacarpophalangeal joints. There are no ulcerations on the fingertips. Muscle exam shows 3/5 strength in the shoulders and hips bilaterally with 5/5 strength of the distal muscles. There are no other rashes and no skin thickening on the rest of the hands, forearms, or trunk. Muscle biopsy shows perimysial inflammation with muscle fiber degeneration. Which of the following autoantibodies is most likely to be present in this patient?