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Question 19#

Over the last 6 weeks a 35-year-old nurse has developed progressive difficulty getting out of chairs and climbing stairs. She can no longer get in and out of the bathtub. She has no muscle pain and takes no regular medications. She does not use alcohol and does not smoke cigarettes. On examination she has a purplish rash that involves both eyelids. There is weakness of the proximal leg muscles. What is the best next diagnostic test?

A. Vitamin B12 level
B. Chest x-ray
C. HLA B27
D. MRI scan of the lumbar spine
E. Creatine kinase (CK)

Correct Answer is E

Comment:

) This woman has dermatomyositis, which typically affects patients aged 40 to 50 who present with progressive proximal myopathy and complain of difficulty arising from chairs, climbing stairs, and getting out of the bathtub. About half of patients with dermatomyositis have the classic heliotrope rash. Lung involvement is common, but cardiac involvement is rare. Almost all patients have an elevated CK. Patients may have the anemia of chronic disease, which is normocytic. The EMG is characteristically abnormal with muscle fibrillations, spontaneous discharges, and sharp waves. In a small percentage of patients, the EMG may be normal. Muscle biopsy is usually diagnostic. High-dose oral corticosteroids are the treatment of choice. Some patients require the addition of methotrexate or azathioprine. Only 25% of patients are cured and most will develop a chronic condition with significant morbidity. Vitamin B12 deficiency causes distal sensory findings (rather than this patient’s proximal motor findings) and would not account for the heliotrope rash. Imaging studies of the lumbar spine would not focus on the primary process, although MRI scanning of the thigh musculature can be a useful study. HLA B27 is diagnostically useful in the spondyloarthropathies such as ankylosing spondylitis; this patient has no back pain or morning stiffness to suggest this diagnosis.