Pretibial Myxedema in a Euthyroid Patient.

Pretibial myxedema (PM) is a rare extrathyroid condition seen in about 0.5 to 4.3 percent of individuals with hyperthyroidism due to Graves' disease, often presenting with associated thyroid orbitopathy. In most cases, patients with PM have elevated levels of thyroid antibodies, such as thyroid peroxidase (TPO), thyroglobulin, and-most especially-thyroid-stimulating hormone receptor antibodies. We present a rare case of biopsy-proven PM in a euthyroid patient with no history of Graves' disease or Hashimoto's disease. TPO and thyroglobulin antibody counts were slightly elevated but less than what is typically seen in PM and thyroid-stimulating hormone receptor antibodies (thyrotrophin-binding inhibitor immunoglobulin) were negative.