A 43-year-old man comes to the office with muscle weakness. His symptoms began 6 weeks ago and are worst in the hips and shoulders. The weakness has had a progressive course so that he is now having difficulty rising from chairs and combing his hair. The patient has had to reduce his regular exercise regimen due to weakness and has requested a modified work schedule for his job as a building maintenance manager. He has no history of spinal injury and no neck pain. Past medical history is insignificant, and the patient takes no medications. Muscle biopsy reveals an endomysial mononuclear infiltrate and patchy muscle fiber necrosis. An autoantibody directed against which of the following antigens is most likely to be seen in this patient?

Question

A 43-year-old man comes to the office with muscle weakness.  His symptoms began 6 weeks ago and are worst in the hips and shoulders.  The weakness has had a progressive course so that he is now having difficulty rising from chairs and combing his hair.  The patient has had to reduce his regular exercise regimen due to weakness and has requested a modified work schedule for his job as a building maintenance manager.  He has no history of spinal injury and no neck pain.  Past medical history is insignificant, and the patient takes no medications.  Muscle biopsy reveals an endomysial mononuclear infiltrate and patchy muscle fiber necrosis.  An autoantibody directed against which of the following antigens is most likely to be seen in this patient?

Quizplus · Accepted Answer

Eductional Objective: Polymyositis and dermatomyositis are characterized by symmetric proximal muscle weakness and are associated with antinuclear and anti-tRNA synthetase (anti-Jo-1) autoantibodies.  Biopsy in polymyositis shows patchy endomysial inflammatory infiltrate (ie, direct invasion of individual muscle fibers), whereas dermatomyositis causes perifascicular inflammation (ie, localized around blood vessels and the septa between muscle fascicles).

A 43-Year-Old Man Comes to the Office with Muscle Weakness