Swelling in the body that's caused by a severely underactive thyroid.

Myxedema is a buildup of protein and water in the body due to a severely underactive thyroid. That condition also is called hypothyroidism. If underactive thyroid is not treated, myxedema can lead to serious health problems. They include myxedema coma, which can be life-threatening.

The most obvious symptom of myxedema is swelling of the skin. This swelling can make the skin look waxy. It most often affects skin on the face, especially around the eyes, on the hands and feet, and just above the collarbone.

Myxedema goes away with treatment for underactive thyroid. That treatment usually includes taking thyroid hormone medicine every day. Myxedema coma requires emergency medical care.