Psoriatic arthritis and myopathy.

We describe a patient with psoriatic arthritis and a myopathy. The myopathy did not follow the time course of topical steroid treatment, nor did the patient display any features of hypercorticolism or local steroid excess. No evidence was found to support the diagnosis of polymyositis. Psoriatic myopathy is an uncommonly described condition. Steroid induced myopathy shares some nonspecific features with psoriatic myopathy, but can be differentiated by the clinical response to cessation of steroid therapy. Myalgia and 24 h urine creatine elevation are 2 features not previously described in association with psoriatic myopathy. The latter appears to correlate with muscle weakness and may be useful in following the course of this disease.