Pretibial myxoedema

Published on 02/04/2015 by admin

Filed under Internal Medicine

Last modified 22/04/2025

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139 Pretibial myxoedema

Instruction

Look at this patient’s legs.

Salient features

History

• As in patients with thyrotoxicosis (p. 137)

Examination

• Red thickened swellings above the lateral malleoli (peau d’orange appearance), which progresses to thickened non-pitting oedema of the feet.

• Examine the following:

• The hands for acropachy (Fig. 136.1), palmar erythema and warm, sweaty palms
• The neck for goitre and thyroidectomy scar
• The eyes for exophthalmos (Fig. 137.1)
• The pulse for tachycardia and atrial fibrillation.

• Tell the examiner that you would like to know whether or not the patient has had any treatment, in particular radioactive iodine.

Remember:

• Almost all cases of thyroid dermopathy are associated with relatively severe ophthalmopathy.

• Usually ophthalmopathy appears first and dermopathy much later.

Diagnosis

This patient has pretibial myxoedema (lesion) with ophthalmopathy and signs of thyrotoxicosis (functional status), which is caused by Graves’ disease.

Questions

What investigations would you do?

Serum thyroxine (T4), triiodothryonine (T3) and thyroid-stimulating hormone (TSH).

How are these lesions treated?

• Intralesional steroids or fluorinated corticosteroids applied under polythene occlusion

• Plasmapheresis

• Cytotoxic therapy

• Octreotide.

Note: Surgical excision should be avoided because surgical scars may aggravate the dermopathy and precipitate recurrence.

Advanced-level questions

What are the types of pretibial myxoedema?

Three major classes of thyroid dermopathy have been identified (Medicine 1994;73:1–7):

• Non-pitting oedema accompanied by hyperkeratosis, pigmentation and pinkish, brownish red or yellowish discoloration of the skin (Fig. 139.1); plaque formation and nodularity are characteristically absent in this group

• Plaque form, consisting of raised, discrete or confluent plaques

• Nodular form, characterized by nodule formation.

image

Fig. 139.1 Chronic pretibial myxoedema in a patient with Graves’ disease and orbitopathy. The lesions are firm and non-pitting, with a clear edge to palpation.

(With permission of Kronenberg et al. 2008.)

Less common types:

• Elephantiasic form

• Polypoid form.

Note: Almost all patients tend to have ophthalmopathy, which is usually severe.

What is the histology of pretibial myxoedema?

• Characteristic features include fraying and oedematous appearance on routine staining with haematoxylin and eosin, and increase of mucinous material staining with alcian blue–periodic acid–Schiff, with resultant connective tissue fibre separation.

• Review of pathology reports does not show any distinguishing microscopic characteristics for various clinical forms of this dermopathy.

What is the pathogenesis of pretibial myxoedema?

• All patients with localized myxoedema have high serum concentrations of TSH receptor antibodies, indicating the severity of the autoimmune condition.

• Occurrence of thyroid dermopathy in areas other than pretibial skin indicates a systemic process.

• Similar to Graves’ eye disease, TSH receptors in the connective tissue may be the antigen responsible for the immune process.

• Both humoral and cellular immune mechanisms are involved in the stimulation of fibroblasts and the production of large amounts of glycosaminoglycans.

• Localization in the pretibial area relates to mechanical factors and dependent position.

What are the recommendations for screening thyroid dysfunction?

It is recommended that adults be screened for thyroid dysfunction by measurement of serum TSH concentration, beginning at age of 35 years and every 5 years thereafter. The indication for screening is particularly compelling in women, but it may also be justified in men as a relatively cost-effective measure in the context of periodic health examination. Individuals with clinical manifestations potentially attributable to thyroid dysfunction and those with risk factors for its development may require more frequent serum TSH testing (Arch Intern Med 2000;1601573–5).

How can hyperthyroidism present in the elderly?

Thyrotoxicosis can present in the elderly with atrial fibrillation, and such patients may lack other common signs of thyrotoxicosis; this is known as apathetic hyperthyroidism. Also low serum TSH is a risk factor for atrial fibrillation the elderly (N Engl J Med 1994;331:1249–52).

Osteoporosis may be the result of subclinical thyrotoxicosis.

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