A 54-year-old female complains of upper leg weakness that has been present for months. Her past medical history is only significant for psoriasis, which was diagnosed two years ago because of a rash on her hands and elbows. She takes no medication, smokes half a pack of cigarettes a day, and drinks socially. The patient's exam is only remarkable for bilateral decreased strength in the hip flexors and quadriceps. There are violaceous plaques on her elbows, knuckles, and around her eyes. Reflexes and sensation are normal. Her complete blood (cell) count and thyroid stimulating hormone are normal. Erythrocyte sedimentation rate, aspartate aminotransferase, and creatine phosphokinase are elevated. Electromyography shows abnormalities at the paraspinous muscles. What is the best treatment for this patient?