Stiff Person Syndrome With Evidence of Nonspecific Focal Myositis Secondary to Sustained Muscle Contraction: A Case Report.

Stiff person syndrome (SPS) is a rare neuroimmunological disorder characterized by progressive muscular rigidity and spasms that affect axial and limb muscles. There have been a few reports that patients with SPS had evidences of polymyositis. There have been no clear explanations about the characteristics of polymyositis in SPS. We report the case of a 36-year-old woman with SPS in association with nonspecific focal myositis secondary to sustained muscle contraction. She presented with stiffness and pain in her extremities, and diazepam and baclofen were ineffective. With immunotherapy, her serum creatinine kinase levels reduced; however, her clinical symptoms progressively worsened. LEVEL OF EVIDENCE: V.