Pretibial Myxedema

Overview

Pretibial myxedema is a skin change in which a complex sugar-protein substance (mucin) builds up in the lower layers of the skin, producing firm, waxy, raised plaques. It most often appears over the front of the shins, which is why it is called pretibial (in front of the tibia), although it can also affect the tops of the feet, the ankles, and occasionally other areas.

Despite the word "myxedema," this condition is not the same as the generalized myxedema of severe hypothyroidism. Pretibial myxedema is almost always a sign of autoimmune thyroid disease, particularly Graves' disease, and it tends to occur alongside thyroid eye disease. It is a relatively uncommon finding and, while usually painless, can affect comfort and appearance.

Symptoms

The condition usually develops gradually and is typically more of a cosmetic concern than a painful one, though some people notice itching or tightness.

• Raised, firm patches or plaques over the shins, often skin-colored, pink, or yellow-brown
• A waxy or "orange-peel" texture, with enlarged pores and prominent hair follicles
• Swelling that does not leave a lasting dent when pressed (non-pitting)
• Itching or a feeling of tightness in the affected skin
• In severe cases, large nodular or wart-like growths, occasionally with a leg that takes on a thick, column-like shape

The changes are usually on both legs and are not generally tender unless they become very pronounced.

Causes

Pretibial myxedema is driven by the same autoimmune process that underlies Graves' disease. Antibodies that stimulate the thyroid also appear to act on cells in the skin called fibroblasts, prompting them to produce excess mucin (mainly hyaluronic acid). This material accumulates in the dermis and draws in water, thickening and distorting the skin.

• Graves' disease: The great majority of cases occur in people who have or have had Graves' disease, an autoimmune cause of an overactive thyroid.
• Autoimmune thyroid activity: High levels of thyroid-stimulating antibodies are typical, even after the thyroid itself has been treated.

Local factors such as trauma, prolonged standing, and leg swelling may help concentrate the changes over the shins.

Risk Factors

• Graves' disease, especially when severe or long-standing
• Thyroid eye disease (the two often occur together)
• High levels of thyroid-stimulating antibodies
• Smoking, which worsens autoimmune thyroid eye and skin disease
• Prior trauma or chronic swelling of the lower legs

Diagnosis

Doctors usually recognize pretibial myxedema from its characteristic appearance and location in a person known to have thyroid disease.

• Clinical examination: The waxy, non-pitting plaques over the shins in someone with Graves' disease are often enough to make the diagnosis.
• Thyroid testing: Blood tests of thyroid hormone levels and thyroid antibodies confirm the underlying autoimmune condition.
• Skin biopsy: Occasionally performed when the diagnosis is unclear; it shows mucin deposits in the dermis.

Treatment

Many mild cases are left untreated because they cause few symptoms and may stabilize on their own. When treatment is wanted for comfort or appearance, options aim to reduce the skin thickening.

• Topical corticosteroids: Strong steroid creams or ointments, often applied under an occlusive dressing, are the usual first-line treatment.
• Compression: Compression stockings or wraps can help reduce swelling and improve the look of the legs.
• Other measures: In resistant cases, doctors may consider corticosteroid injections or other immune-modulating approaches.

Good control of the underlying thyroid disease is part of overall care, although treating the thyroid does not always clear the skin changes. Stopping smoking is strongly encouraged.

Prevention

There is no guaranteed way to prevent pretibial myxedema, but some steps may lower the risk or limit severity.

• Avoid smoking, which is a major modifiable risk factor for Graves'-related eye and skin disease
• Work with your doctor to keep autoimmune thyroid disease under control
• Protect the lower legs from injury and manage chronic leg swelling

When to See a Doctor

See a doctor if you notice firm, waxy, or thickened patches developing over your shins, especially if you have a known thyroid problem. It is also worth being evaluated if such skin changes appear alongside symptoms of an overactive thyroid, such as a fast heartbeat, weight loss, tremor, or bulging eyes, so the underlying condition can be assessed and managed.

Related Topics

Frequently Asked Questions

References

1. Mayo Clinic. Graves' disease — Symptoms and causes.
2. American Thyroid Association. Graves' Disease.
3. MedlinePlus, U.S. National Library of Medicine. Graves disease.
4. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Graves' Disease.