Myxedematous

Myxedematous is the term used to describe changes associated with myxedema, a form of non-pitting edema that occurs primarily in severe hypothyroidism. It reflects mucopolysaccharide (glycosaminoglycan) deposition in the dermis and subcutaneous tissues, leading to swollen, thickened skin and a characteristic facial puffiness.

Pathophysiology involves accumulation of glycosaminoglycans such as hyaluronic acid and chondroitin sulfate in the dermis, with increased water retention and reduced lymphatic drainage. The edema is typically non-pitting and is often accompanied by dry, coarse skin, hair thinning, and other signs of hypothyroidism.

Clinically, myxedematous edema presents as facial puffiness, periorbital swelling, and thickened tongue and lips, with non-pitting edema of the trunk and limbs. Other hypothyroid signs may include fatigue, cold intolerance, weight gain, constipation, and slowed heart rate.

Causes are most commonly primary hypothyroidism (for example, Hashimoto thyroiditis) but can occur with secondary hypothyroidism. Less commonly, edema with mucopolysaccharide deposition can be seen in other thyroid or endocrine disorders. Pretibial myxedema is a related but distinct condition associated with Graves disease and local autoimmune effects.

Diagnosis rests on clinical suspicion supported by thyroid function tests showing low free T4 with elevated TSH in primary hypothyroidism; thyroid autoantibodies may be present. Imaging or further tests may be used to evaluate the underlying thyroid disease.

Management centers on treating the underlying hypothyroidism with thyroid hormone replacement (levothyroxine). Edema tends to improve as TSH normalizes, though diuretics are not routinely required. In suspected myxedema coma, urgent hospital care is necessary. With appropriate therapy, myxedematous edema often improves over weeks to months.