PSAT358 Graves’ Disease Complicated by Post-Operative Graves’ Ophthalmopathy and Pretibial Myxedema
Authors: Bowens Brendan , LaChance David , Huyhn James , Shakir Mohamed , Hoang Thanh 
Published: November 2022

Abstract

Introduction
Approximately 60-80% of all hyperthyroid cases are caused by Graves’ disease, which is mediated by thyroid receptor antibodies. The prevalence of Graves Ophthalmopathy (GO) and pretibial myxedema is 0.15/10,000 and occurs in less than 5% of patients with Graves’ disease. We report a rare case of Graves disease with development of GO and pretibial myxedema post-thyroidectomy.

Case Report
A 51-year-old African American female with no medical history presented with tachycardia, palpitations, heat intolerance, weight loss, anxiety, and panic attacks. She was found to have an undetectable TSH, free T4 6.1 ng/dL (0.93-1.7 ng/dL), total T3 332.4 ng/dL (80-200 ng/dL), thyroid stimulating immunoglobulin (TSI) 19.50 IU/L (0.00-0.55 IU/L) and thyrotropin receptor antibody (TRAb) 27 U/L (&lt;1.0 U/L). She denied vision changes, eye irritation or pain. Her initial exam revealed no exophthalmos, chemosis or reduced ocular range of motion. Thyroid ultrasound revealed an enlarged, heterogeneous, hypervascular thyroid. Treatment was initiated with atenolol and methimazole to achieve euthyroidism. Patient elected for total thyroidectomy. Within 3 months after thyroidectomy, she developed hyperpigmentation of bilateral anterior lower extremities with firm, compressible papules and scattered coalescent plaques. These lesions worsened and progressed over time. Skin biopsy revealed increased mucin in the papillary and reticular dermis and the subcutaneous soft tissue, consistent with pretibial myxedema. She also developed GO with exophthalmos, spontaneous orbital pain and edema and erythema of her eyelids and conjunctiva. Current plan of care is treatment with teprotumumab infusions with possibility of orbital decompression surgery.

Conclusion
The occurrence of GO and pretibial myxedema in a patient with Graves’ disease status post thyroidectomy is very uncommon, occurring in less than 5% of patients with Graves’ disease, especially since the source of the antigen for GO has been eliminated. Pretibial myxedema occurs as a result of the deposition of glycosaminoglycans (GAG) secreted by fibroblasts which have been found to express thyroid stimulating hormone receptor (TSHR) leading to deposition of mucin in the papillary and reticular dermis. In a similar manner, orbital accumulation of GAG and subsequent expansion of retrobulbar tissue leads to the clinical manifestation of exophthalmos. Despite thyroidectomy, the thyroid antibodies themselves may lead to the accumulation of GAG which may lead to the development of GO in the absence of a thyroid. Pretibial myxedema management depends on the symptomatology, as it may be asymptomatic or associated with pruritus and irritation. Topical or intralesional glucocorticoids are used to treat symptomatic cases, though there is a 30% chance of recurrence. Teprotumumab has been approved to treat GO and only case reports of teprotumumab leading to improvement of pretibial myxedema have been described. More data is needed to determine its efficacy as a treatment option for pretibial myxedema.
Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.