Pretibial Myxedema is an infiltrative dermopathy, resulting as a rare complication of Grave's disease, with an incidence rate of about 1-4% in patients.It usually presents itself as a non-localised, non-pitting edema and thickening of the skin which usually occurs on the anterior aspect of the lower legs spreading to the dorsum of the feet. In advanced cases, this may extend to the upper trunk (torso), upper extremities, face, neck, and ears.
The lesions are known to resolve very slowly. It occasionally occurs in non-thyrotoxic Grave's disease, autoimmune thyroiditis, and stasis dermatitis. The serum contains circulating factors which stimulate fibroblasts to increase synthesis of glycosaminoglycans.
A biopsy of the affected skin reveals mucin in the mid- to lower- dermis. There is no increase in fibroblasts. Over time, secondary hyperkeratosis may occur, which may become verruciform. Many of these patients may also have co-existing stasis dermatitis. Elastic stains will reveal a reduction in elastic tissue