History
A 51-year-old man presents to his GP with progressive swelling of the lower legs. He works as a teacher and had initially ignored the changes, assuming they resulted from standing all day. However, the swelling did not recede overnight and his shins were becoming ‘lumpy’. He feels otherwise well in himself, reporting plenty of ‘energy’ in the classroom, although he has lost weight recently which he can’t explain. There is a family history of varicose veins and diabetes. He takes occasional paracetamol for headaches and ‘tired eyes’ at the end of the day.
Examination
There are bilateral pigmented plaques of the anterior shins, worse on the left than the right, and the associated swelling does not pit on firm pressure (Fig. 45.1). There is no evidence of varicose veins. He has mild proptosis and clubbing, and is of slim build. There is no obvious swelling in his neck. His scalp and nails are normal.
Questions
• What investigations would you request?
• What is the diagnosis?
• How would you manage this patient?
Medicine
One of the many exciting aspects of dermatology is the ability of the trained eye to observe a cutaneous sign and diagnose a systemic disease – this is one such case. The cutaneous findings of pretibial myxoedema (thyroid dermopathy) point to an underlying thyroid disorder most commonly that of autoimmune Graves’s thyrotoxicosis. Pretibial myx- oedema may also be seen in Hashimoto’s thyroiditis, and primary hypo-/euthyroidism. The exact pathogenesis of the skin changes is yet to be delineated, however it is thought that through an antibody-mediated process skin fibroblasts are stimulated to produce excessive quantities of glycosaminoglycans, which leads to deposition of hyaluronic acid in the skin.
Classically, the development of pretibial myxoedema is insidious with the development of non-pitting oedema over the anterior and lateral shins. Chronic oedema leads to firm indurated pigmented plaque-like areas which may become slightly tender. Skin changes usually follow eye disease and the diagnosis of thyroid disease, however skin changes may be the first sign. Many patients with pretibial myxoedema have thyroid eye disease with proptosis, lid retraction and periorbital oedema. Thyroid acropachy (clubbing) is common in patients with pretibial myxoedema, and onycholysis of the 4th and 5th fin- gernails may also occur.
Investigations should include thyroid function tests, which usually show very high levels of free thyroxins T4 and T3, and low levels of thyroid-stimulating hormone. Thyrotropin receptor and antithyroglobulin antibodies are usually positive. Skin biopsy is not usually recommended, as healing of the biopsy site may be poor leading to chronic ulceration.
Treatment of pretibial myxoedema is unsatisfactory. Topical or intra-lesional corticoster-oids and compression stockings can help to improve the appearance, lessen discomfort and prevent possible ulceration. Trials of intra-lesional octreotide have had mixed success at reducing the levels of hyaluronic acid in the affected skin. Surgery should be avoided as healing is usually poor.
Radioactive iodine is still considered the first-line treatment for Graves’s disease with subsequent thyroid replacement necessary in a proportion of patients commencing approximately two months following thyroid gland destruction. For severe Graves’s dis-ease ophthalmopathy, high-dose corticosteroids may be required or even orbital decom-pression surgery.
KEY POINTS
• Pretibial myxoedema occurs in about 15 per cent of patients with underlying thyrotoxic Graves’s disease.
• Deposition of hyaluronic acid in the skin leads to oedematous plaques of the shins.
• Pretibial myxoedema is difficult to manage, however compression and topical steroids may help.
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