MKSAP Quiz: follow-up visit for dermatomyositis
MKSAP Quiz: follow-up visit for dermatomyositis
A 73-year-old man is evaluated during a follow-up visit for dermatomyositis. His condition was diagnosed 6 months ago. His serum creatine kinase level at that time was 3,000 U/L. His disease responded well to prednisone, 60 mg/d, which was gradually tapered to 20 mg/d. He also takes azathioprine, 150 mg/d; alendronate; and calcium and vitamin D supplements. He mentions that his muscle weakness has increased over the past month but denies myalgia, tenderness, or side effects related to azathioprine.
On physical examination, there are cushingoid facial changes. There is no rash. Muscle strength in the hip flexors and upper arms is 4/5. The muscles of the neck, back, upper arms, and legs are not tender to palpation.
Laboratory studies reveal a leukocyte count of 9,800/µL (9.8 × 109/L) and a serum creatine kinase level of 170 U/L.
Which of the following is the most appropriate next step in this patient's management?
A. Decrease prednisone dosage
B. Increase azathioprine dosage
C. Substitute cyclosporine for azathioprine
D. Substitute methotrexate for azathioprine
MKSAP Answer and Critique
The correct answer is A) Decrease prednisone dosage. This item is available to MKSAP 15 subscribers as item 58 in the Rheumatology section.
This patient most likely has corticosteroid-induced myopathy, and the most appropriate next step in his management is to decrease the prednisone dosage. He has progressive muscle weakness, but the significant decrease in his creatine kinase level suggests that his dermatomyositis is well controlled. Improvement in muscle strength typically is preceded by improvement in the creatine kinase level, but the discrepancy between this patient's findings on laboratory studies and symptoms is highly suggestive of a secondary cause for his weakness.
Corticosteroid-induced myopathy should be suspected in patients with polymyositis or dermatomyositis treated with corticosteroids who develop progressive weakness despite significant improvement in muscle enzyme levels. This patient's cushingoid features also are consistent with this condition.
The most appropriate management of a patient whose clinical presentation raises concern for corticosteroid-induced myopathy is to decrease the corticosteroid dosage and closely monitor the creatine kinase level for elevations. If corticosteroid-induced myopathy is causing this patient's symptoms, his muscle weakness should begin to resolve 3 to 4 weeks after his prednisone dosage is decreased.
Increasing the azathioprine dosage would not be warranted in a patient with dermatomyositis whose creatine kinase level is not significantly elevated. Furthermore, this intervention would not directly address this patient's underlying corticosteroid-induced myopathy.
Cyclosporine is an adjunct or substitute for methotrexate and azathioprine in patients in whom these agents are ineffective in the treatment of myositis or in those who cannot tolerate these agents. This patient is tolerating azathioprine, and there is therefore no need to add or substitute cyclosporine.
Methotrexate is effective in the treatment of inflammatory myositis and is an alternative steroid-sparing drug to azathioprine. However, the patient's condition is responsive to his current medication regimen of corticosteroids and azathioprine, and substituting methotrexate is not likely to offer any advantage to a patient with corticosteroid-induced myopathy.
Key Point
- Corticosteroid-induced myopathy should be suspected in patients with polymyositis or dermatomyositis treated with corticosteroids who develop progressive weakness despite significant improvement in muscle enzyme levels.