pretibial myxedema

myxedema /myx·ede·ma/ (-sĕ-de´mah) a dry, waxy type of swelling (nonpitting edema) with abnormal deposits of mucin in the skin (mucinosis) and other tissues, associated with hypothyroidism; the facial changes are distinctive, with swollen lips and thickened nose.myxedem´atous

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congenital myxedema  cretinism.

papular myxedema  lichen myxedematosus.

pituitary myxedema  that due to deficient secretion of the pituitary hormone thyrotropin.

pretibial myxedema  localized edema associated with preceding hyperthyroidism and exophthalmos, occurring typically on the anterior (pretibial) surface of the legs, the mucin deposits appearing as both plaques and papules.

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pretibial myxedema

n.

See circumscribed myxedema.

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myxedema [mik″sĕ-de´mah]

a condition resulting from advanced hypothyroidism, or deficiency of thyroxine; it is the adult form of the disease whose congenital form is known as cretinism. adj., adj myxedem´atous.

Myxedema may be caused by lack of iodine in the diet; by atrophy, surgical removal, or a disorder of the thyroid gland; by destruction of the gland by radioactive iodine; or by deficient excretion of thyrotropin by the pituitary gland. It is marked primarily by a growing puffiness or “sogginess” of the skin, nonpitting edema, abnormal deposits of mucin in the skin, and distinctive facial changes such as swollen lips and a thickened nose.

Because thyroxine plays such an important role in the body's metabolism, lack of this hormone seriously upsets the balance of body processes. Among the symptoms associated with myxedema are excessive fatigue and drowsiness, headaches, weight gain, dryness of the skin, sensitivity to cold, and increasing thinness and brittleness of the nails. In women, menstrual bleeding may become irregular. Medical tests reveal slow tendon reflexes, low blood iodine, below-normal metabolism, and abnormal uptake of radioactive iodine by the thyroid.

The body's defenses against infection also are weakened. If the patient has heart disease, it may worsen. Upset of the functions of the adrenal glands may become critical. In time, if myxedema is not brought under control, progressive mental deterioration may result in a psychosis marked by paranoid delusions.

Myxedema is treated by administration of thyroid extract or similar synthetic preparations. If treatment is begun soon after the symptoms appear, recovery may be complete. Delayed or interrupted treatment may mean permanent deterioration. In most instances, treatment with thyroid hormones or synthetics must be continued throughout the patient's lifetime.

pretibial myxedema localized skin lesions associated with preceding hyperthyroidism, found most often on the front of the legs. It is almost always associated with graves' disease, occurring in 0.5 to 5 per cent of patients. Called also thyroid dermopathy.