Abstract: Objective To study polymyositis and differential diagnosis of hypothyroid myopathy.Methods The clinical manifestations and laboratory parameters of 12 patients with polymyositis and 10 patents with hypothyroid myopathy were analyzed and the relevant literature was reviewed.Results Hypothyroid myopathy and polymyositis show similar symptoms of muscle dysfunction and elevations of serum muscle enzymes,but can be distinguished by differences in levels of acute inflammation indexes,types of autoantibodies,muscle pathology,and thyroid function tests.Conclusion Thyroid function tests should be routinely performed in all patients with muscle weakness or elevations of muscle enzymes.

Key words: polymyositis, hypothyroid myopathy