The association between dermatomyositis and papillary thyroid cancer: a case report.

We report the case of a 66-year-old woman who developed progressive proximal muscle weakness and papillary thyroid cancer. After a thyroidectomy, she was treated with intravenous methylprednisolone pulse therapy and oral prednisolone followed by tacrolimus therapy. However, her clinical symptoms and laboratory data did not improve sufficiently. Therefore, we administered intravenous immunoglobulin. As a result, she regained substantial muscle strength along with complete normalization of serum muscle enzymes and showed no evidence of recurrence of papillary thyroid cancer or exacerbation of dermatomyositis (DM). Although there is controversy as to whether papillary thyroid cancer is involved in DM, the results of this study support a connection between these two conditions.