Pretibial myxedema is most closely associated with which thyroid disorder?

• A. Hashimoto's thyroiditis
• B. Graves disease
• C. Hypoparathyroidism
• D. Addison's disease

Answer: (B)

Pretibial myxedema is a skin manifestation tied to Graves disease, an autoimmune form of hyperthyroidism. In Graves, antibodies stimulate the TSH receptor not only in the thyroid but also on dermal fibroblasts. This triggers excessive production of glycosaminoglycans, especially hyaluronic acid, in the skin, leading to localized, thickened, nonpitting edema on the shins.

This condition is a clue that points to Graves disease rather than other thyroid-related or adrenal disorders. Hashimoto's thyroiditis causes autoimmune hypothyroidism and does not typically produce pretibial myxedema. Hypoparathyroidism and Addison's disease involve different hormonal systems and do not commonly present with this skin change.