Hypertrophic plaques on the legs

This man in his 70s presented with a four year history of progressive non-pitting, hypertrophic plaques on both legs (fig 1). He did not report any fatigue, palpitations, changes to his weight, or intolerance to heat or cold. Blood test results indicated primary hypothyroidism, with positive thyroid peroxidase antibodies, and positive thyroid stimulating hormone (TSH) receptor antibodies. Ultrasonography detected a multinodular goitre. A skin biopsy showed abundant dermal mucin, compatible with pretibial myxoedema (PTM).