Improvement of Pretibial Myxedema Following Administration of Teprotumumab

Pretibial myxedema (PTM) is a rare complication of Graves’ disease. It is characterized by non-pitting edema with hyperpigmented hyperkeratotic papules and plaques on bilateral lower legs. Effective treatments for patients with PTM are lacking.The etiology of PTM is unknown; however, it may be similar to the mechanism of thyroid-associated ophthalmopathy (TAO). Activated fibroblasts produce inflammatory cytokines and synthesize excessive glycosaminoglycans (GAG) that accumulate in the dermis and subcutaneous tissue. A recent, novel pathway implicates IGF-1 receptor as a mediator in this process. We present two patients with refractory PTM that improved following treatment with teprotumumab, an IGF-1 receptor inhibitor approved for use inTAO.