ODP502 Nodular Pretibial Myxedema without Graves’ Orbitopathy: A Case Report

Abstract Background Nodular myxedema is an uncommon skin manifestation of autoimmune thyroid disease. Almost always associated with significant orbitopathy from the deposition of glycosaminoglycans by stimulated fibroblasts. Clinical Case A 57-year-old male presented to dermatology clinic with multiple, non-tender, non-erythematous, nodular lesions of the distal left leg, which had been increasing in size and number over the past one year. The initial clinical impression was lipoma, versus leiomyoma, versus pilomatricoma. The pathology report from punch biopsy of one of the lesions revealed diffuse dermal mucin deposition, consistent with pretibial myxedema. The patient was then referred to endocrinology. His symptoms included increasing fatigue and weight gain of 20.4 kilograms over the last 7 years. He had long-standing history of untreated hypothyroidism and tobacco use disorder. There was no known history of hyperthyroidism, neither thyromegaly, acropachy, nor any signs of orbitopathy were found on examination. Laboratory tests revealed a mildly elevated TSH (5.491 uIU/ml, reference 0.450-5.491 uIU/ml), normal free thyroxine (0.98 ng/dl, reference 0.45-1.80 ng/dl) and elevated anti-microsomal antibody (66. 0 IU/mL, reference <9. 00 IU/ml). Following the pathology report, thyroid stimulating immunoglobulin was requested and found to be elevated (322%, reference <140%). Thyroid ultrasound showed estimated volume of 5. 04 and 2.96 ml for the right and left thyroid lobes, respectively, and only one sub-centimeter nodule. Treatment with levothyroxine was started. Conclusion Thyroid dermopathy, including pretibial myxedema, is attributed to high serum concentrations of thyroid stimulating immunoglobulin leading fibroblasts to deposit mucopolysaccharides in the papillary and reticular dermis. The resulting nonpitting edema can occur anywhere in the skin, despite its notorious penchant for the anterior tibial region. Thyroid dermopathy is seen in 4.3% of patients with Graves’ disease in general, and 15% of patients with Graves’ orbitopathy 1 . Thyroid dermopathy is very rare in the absence of concurrent orbitopathy. Here we present a very unusual case of biopsy-confirmed nodular pretibial myxedema in the absence of current or remote history of known hyperthyroidism, and without any apparent orbitopathy. Presentation: No date and time listed