Pretibial Myxedema Associated with Euthyroid Hashimoto’s Thyroiditis: A Case Report

Abstract

A 63-year-old woman presented with a six month history of a large pruritic plaque which was present over both her legs and feet. The lesions had first appeared over her right leg, followed by involvement of left leg. She denied fatigue, heat intolerance, hand tremor, constipation, unexplained weight gain or change in voice. Her past medical history included Type-2 diabetes mellitus, which was currently diet controlled and hypertension, of two year's duration. Her current medications included an angiotensin receptor blocker. Her physical examination revealed a non-tender, firm, nodular thyroid swelling and exophthalmos. Her cutaneous examination showed a well defined, indurated, erythematous to skin coloured non-tender plaque over both anterolateral aspects of legs. On left side, lesions extended upto middle of the leg and on the right side, just above the ankle, extending to involve bilateral feet, but sparing the toes [Table/ Fig-1]. There was no clubbing, hyperhidrosis or hypertrichosis.Thyroid function test showed thyroid-stimulating hormone (TSH)-2.25 mu/L (0.27-4.20 mu/L), free triiodothyronine (T3) -1.54 nmol/L (1.3-3.1 nmol/l), free thyroxine (T4) -93.62 nmol/l (66-181 nmol/l), thyroglobulin antibodies (AbTG) titre-190 IU/mL(0-35 IU/mL) and Anti-TPO antibody levels of >1000 IU/mL (0-35iu/ ml). Other haematological and biochemical investigations, including serum creatinine, lipid profile and plasma glucose were within normal limits. Keeping in mind PM, chronic dermatitis and lichen myxedematosus as differentials, a skin biopsy was taken from left leg. Histopathology showed a normal epidermis, collagen fibres in reticular dermis, which were mildly separated by deposits of mucin, and mild perivascular lymphocyte infiltration. These changes were suggestive of PM [Table/ Fig-2].Ultrasound examination of thyroid showed diffusely heterogeous and bulky cystic areas with increased vascularity. Few subcentimetric sized lymph nodes were noted, which were bilateral at level 2 and level 3, which suggested a possibility of Thyroiditis. Fine needle aspiration biopsy taken from thyroid swelling showed oxyphilic cells with round nuclei and moderate to marked anisocytosis, prominent nucleoli and abundant eosinophilic granular cytoplasm. Few multinucleated giant cells with occasional clusters of epitheloid histiocytes were present, which favoured changes of Hashimoto's thyroiditis. The lesions regressed after 4 sittings, with monthly intralesional triamcinolone acetonide injections, 10 mg/ml, 0.5-1.0 ml per lesion. DisCussionPM is a well-defined cutaneous mucinosis which is characterized by increased amounts of acid glycosaminoglycans in the dermis. It is a rare clinical finding which is often referred to as localized myxedema or thyroid dermopathy. It is an autoimmune manifestation seen in 5 -10% of patients with Graves thyrotoxicosis [1]. PM has a gradual onset and it typically develops 12 to 24 months after the diagnosis of thyrotoxicosis. It tends to affect older adults, showing a peak incidence in the sixth decade of l...

Prevalence and Clinical Characteristics of Pretibial Myxedema in Chinese Outpatients With Thyroid Diseases

“…Even if PTM simultaneously appeared in thyroid dysfunction such as hyperthyroidism or hypothyroidism, PTM would not relieve after correcting the thyroid dysfunction in our investigation. However, the onset of PTM in euthyroid patients has been reported in six cases [14][15][16]. In our investigation, two PTM cases occurred in the euthyroid state before the appearance of hyperthyroidism of Graves' disease.…”

Pretibial myxedema in a euthyroid patient

“…To the best of our knowledge, PM in euthyroid patients has also been reported in another six cases in the literature [3,[5][6][7][8][9]. The absence of the commonly assessed thyroid autoantibodies (TPO-Ab, Tg-Ab, TSI, TBII) was evident in two of them [5,6] and positive thyroid autoantibodies (either TSI or TPO-Ab, Tg-Ab,) in another two [3,7], while in two other cases, there were no available data regarding thyroid autoantibody tests [8,9]. There is no plausible explanation for this rare manifestation of PM in our patient.…”

“…Histopathology usually shows deposition of mucin/ glycosaminoglycan among the dermal collagen fibers in the dermis, along with lymphocytic infiltration in most cases, without affecting the epidermis [2,4]. The differential diagnosis includes simple edema as a result of fluid retention or venus insufficiency, chronic lichenified dermatitis, hypertrophic lichen planus, urticarial phase of bullous pemphigoid or, rarely, papular, follicular, or reticular erythematous mucinosis [2,3].…”

“…PM usually occurs during the hyperthyroid state of GD [1,2]. PM has also rarely been described in patients with Hashimoto's thyroiditis [3]. We present a rare case of a biopsy-proven PM manifesting in a euthyroid patient with no history of GD or Hashimoto's thyroiditis.…”

Morphological Diversity of Pretibial Myxedema and Its Mechanism of Evolving Process and Outcome: A Retrospective Study of 216 Cases

“…As to outcome of PTM, generally accepted view was that it was self-limited and lesions usually resolved spontaneously without requirement of therapy [ 7 , 8 ]. This view was contradicted to the clinical reality.…”