Endocrine Abstracts

Introduction: Pretibial myxedema (PM) is a rare extrathyroidal manifestation of Graves’ disease, with most patients being in hyperthyroid state. PM has also rarely been described in Hashimoto thyroiditis.

Case report: A 61-year old Caucasian woman attended our outpatient dermatology clinic for evaluation and management of bilateral erythema, involving the lower two-thirds of the pretibial regions. She reported appearance of the same lesion 11 years ago.

Medical history was remarkable for subtotal thyroidectomy due to non-toxic multinodular goiter, breast cancer, type 2 diabetes mellitus and arterial hypertension. There was no history of thyrotoxicosis or ophthalmopathy. No smoking or alcohol was reported.

Clinical examination revealed the presence of itchy bilateral, edematous pretibial erythema, with ‘peau d’; orange’ appearance. No signs of ophthalmopathy or acropathy were observed.

Laboratory investigation showed: TSH: 0.89 mIU/l (normal range: 0.4–4) and free-thyroxine: 1.32 ng/ml (normal range: 0.8–1.5). Thyroid peroxidase and thyroglobulin antibodies were negative, as well as, thyroid stimulating and inhibitory immunoglobulins (TSI and TBII, respectively).

Neck ultrasonography revealed the presence of significant thyroid remnant, with mild heterogeneity regarding its echogenic structure, without nodules.

A skin biopsy from the pretibial skin was performed which showed edema of the reticular dermis presenting as empty slit-like spaces separating collagen fibers, with normal fibroblasts. Stellate fibroblasts (myofibroblasts) in papillary dermis and perivascular infiltrate of lymphocytes were observed. The histochemical stain Alcian blue pH 2.5 showed mild increase of acid mucopolysaccharides in papillary dermis. These findings were consistent with PM.

The patient was successfully managed with topical application of corticosteroids, with significant amelioration of her lesions one month later.

Conclusions: This is a rare case of PM in a euthyroid patient, with no evidence of thyroid autoimmunity. Six other euthyroid PM cases have been reported (one with positive TSI, two with negative TSI and not measured in the other cases).