Myxoedematous infiltrate of the forehead in treated hypothyroidism

A 42-year-old man presented with a 3 month history of erythema and thickening of the forehead skin. He had been diagnosed as hypothyroid 10 years previously and treated with thyroxine at adequate dosage, according to thyroid function tests. Histology confirmed a myxoedematous infiltrate. The forehead is an unusual site for deposition of mucin and the late appearance, 10 years after treatment, is also uncharacteristic. Myxoedema in the usual pretibial site is a feature of Graves' disease. This man, however, had been hypothyroid with no features of Graves' disease suggesting that there are additional factors other than thyroid status and thyroid autoimmune disease which may be important in the development of myxoedematous infiltrates.