Pretibial myxedema

Pretibial myxedema
Classification and external resources
File:Pretibial-myxedema-16.jpg Shins of a patient with myxedema showing characteristic orange peel appearance
ICD-9	242.9
DiseasesDB	25147
eMedicine	derm/347

Pretibial myxedema (myxoedema (UK)) is an infiltrative dermopathy, resulting as a rare complication of Graves' disease, with an incidence rate of about 1-4% in patients.

Presentation

It usually presents itself as a waxy, discolored induration of the skin—classically described as having a so-called peau d'orange (orange peel) appearance—on the anterior aspect of the lower legs, spreading to the dorsum of the feet, or as a non-localised, non-pitting edema of the skin in the same areas. In advanced cases, this may extend to the upper trunk (torso), upper extremities, face, neck, back, chest and ears.

The lesions are known to resolve very slowly. application of petroleum jelly on the affected area could relieve the burning sensation and the itching. It occasionally occurs in non-thyrotoxic Graves' disease, Hashimoto's thyroiditis, and stasis dermatitis. The serum contains circulating factors which stimulate fibroblasts to increase synthesis of glycosaminoglycans.

Diagnosis

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.