Pretibial Myxoedema — SCE Dermatology MCQ

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ModerateConnective Tissue & VasculitisPretibial MyxoedemaSCE Dermatology

A 50-year-old man presents with pretibial myxoedema. He has bilateral raised waxy nodules and plaques on his anterior shins with non-pitting oedema. He has Graves disease with exophthalmos. What is the underlying pathogenesis?

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Correct answer: D — Thyroid-stimulating hormone receptor antibodies stimulate fibroblast hyaluronic acid production in the pretibial dermis

Pretibial myxoedema (thyroid dermopathy) is caused by TSH receptor antibodies (which also cause Graves thyrotoxicosis and thyroid eye disease) stimulating dermal fibroblasts in the pretibial area to overproduce glycosaminoglycans (particularly hyaluronic acid), causing dermal thickening and non-pitting oedema. The predilection for the pretibial area may relate to local factors (trauma, dependent position, reduced lymphatic drainage). It occurs almost exclusively in Graves disease (both during thyrotoxicosis and after treatment). Treatment includes potent topical corticosteroids under occlusion, compression, and rarely intralesional steroids. Thyroid acropachy (periosteal new bone formation with digital clubbing) is a rare associated feature.

Reference: BAD 2019; Endocrinology Review