Myxedema

Myxedema refers to a waxy swelling of the skin classically seen in hypothyroidism.

Terminology

Occasionally myxedema is also used as a synonym for hypothyroidism or as a shortening for myxedema coma.

Historically the term myxedema has also been used for a localized form of skin thickening, especially of the shins (hence pretibial myxedema), seen in some forms of hyperthyroidism, especially Graves disease. This has been renamed and is now properly known as thyroid dermopathy .

Clinical presentation

Typically the edema is non-pitting in nature (cf. pitting edema of congestive cardiac failure).

Pathology

Pathologically, myxedema is due to a number of interrelated processes :

• accumulation of glycosaminoglycans, primarily hyaluronic acid, which due to its highly polar nature, may attract more than 1000 times its own weight in water
• mucin deposition
• escape of albumin into the extracellular space
• poor lymphatic drainage

History and etymology

Myxedema is derived from Greek roots. 'Myxo' comes from the Greek word μυξα (myxa) meaning mucus, and 'edema' from the Greek word οιδημα (oidema) meaning swelling .