Myxedema
Overview
Myxedema (British English: myxoedema) is a skin and tissue disorder usually due to severe prolonged hypothyroidism. Hypothyroidism can be caused by atrophic disease, Hashimoto's thyroiditis, surgical removal of the thyroid, and rarer conditions. Partial forms of myxedema, especially of the lower legs (called pretibial myxedema), occasionally occur in adults with Graves' disease, a cause of hyperthyroidism; or also Hashimoto's thyroiditis without severe hypothyroidism.
Symptoms
Myxedema usually presents with the symptoms of hypothyroidism. Dermatological symptoms include:
- Jelly-like infiltrations in subcutaneous tissues
- Skin thickening
- Coarse skin
- Dry skin (xeroderma)
- Yellow skin (carotenoderma)
- Non-pitting edema
- Eye puffiness
Additionally, there can be
- Joint pain
- Intense cold intolerance
- Drowsiness, profound lethargy
- Slurred speech
Finally, when untreated, unconsciousness and coma
Causes
Myxedema, stemming from both the hyperthyroid and hypothyroid conditions, results from the accumulation of increased amounts of hyaluronic acid and chondroitin sulfate in the dermis in both lesional and normal skin. The mechanism that causes myxedema is still not yet understood, although animal model studies suggest that thyroid hormones affect the synthesis and catabolism of mucopolysaccharides and collagen by dermal fibroblasts. The fibroblasts in the orbital and pretibial dermis share antigenic sites that underlie the autoimmune process that causes Graves' disease. This cross-reaction may contribute to the development of myxedema long after normal levels of thyroid hormones have been restored by treatment.
Prevention
There is no prevention for hypothyroidism. However, screening tests in newborns can detect congenital hypothyroidism.
Diagnosis
A physical examination will show:
- Brittle nails
- Coarse facial features
- Firm swelling of the arms and legs
- Low blood pressure
- Low temperature
- Mental slowing
- Muscle atrophy
- Pale, yellow skin
- Separated sutures
- Slow heart rate
- Slow relaxation of muscles during reflex tests
- Thin and brittle hair
A chest x-ray may show an enlarged heart. Laboratory tests to determine thyroid function include:
- T4 test
- Serum TSH
Other findings on lab tests may include:
- Anemia on a complete blood count (CBC)
- Increased cholesterol levels
- Increased liver enzymes
- Increased serum prolactin
- Low serum sodium
Prognosis
With treatment, most people will return to normal. However, you will need to take medication for the rest of your life. Myxedema coma can result in death.
Treatment
Treatment for myxedema is difficult. Systemic or intralesional glucocorticoids, topical glucocorticoids under occlusion or high-dose intravenous immunoglobulin have been reported to offer some relief to patients. Treatment should follow correction of the original hyperthyroidism/hypothyroidism. Levoxothyroxine replacement for hypothyroidism due to Hashimoto's Disease can be very effective.