SUN-585 A Case of Atypical Myxedema in Hypothyroidism

Background: Myxedema, also known as thyroid dermopathy, is a skin finding in thyroid disease characterized by papules or nodules overlying a non-pitting induration, with atrophy of overlying skin (1). It is more common in Graves’ disease (~4% of patients) but can rarely be seen in hypothyroidism as well (1). Clinical Case: A 33-year-old African American female with past medical history of obesity presented to dermatology clinic for evaluation of a diffuse, non-resolving papulonodular rash on her face, trunk, groin, and buttocks. Biopsy was taken from the right flank, and laboratory studies were obtained. She was started empirically on topical ketoconazole and oral doxycycline. The biopsy showed a positive mucin stain, and psoriasiform hyperplasia with slight spongiosis in the epidermis, consistent with myxedema. Laboratory studies revealed thyroid stimulating hormone (TSH) >100 mcIU/L (reference range, 0.34 - 5.60), free thyroxine (FT4) of 0.34 ng/dL (reference range, 0.58 - 1.64), free triodothyronine (FT3) of 1.2 pg/mL (reference range, 2.0 - 4.4), and thyroid peroxidase antibody level of 274 IU/mL (reference range, 0 - 34), and she was urgently referred to endocrinology clinic. During her endocrinology clinic visit, her review of systems was positive for weight gain, cold intolerance, fatigue, lower extremity edema, rash, intermittent constipation, and hair loss. She had no personal or family history of thyroid disease. Physical exam revealed thick hyperpigmented macerated plaques in the skin folds on her trunk and antecubital fossae. Thyroid was normal in size, with no palpable nodules. Weight was 157 kg, with BMI of 55.9. Hemoglobin A1c was normal at 4.5%. She was started on levothyroxine 250 mcg daily. On follow up two months later, her TSH was 0.99 mcIU/L and FT4 was 1.38 ng/dL. Clinical symptoms of constipation and fatigue had improved, and there was improvement in the rash. Conclusion: Myxedema is caused by accumulation of glycosaminoglycans in the dermis, secreted by fibroblasts. It is hypothesized that destruction of thyroid tissue may release an antigen that cross-reacts with an antigen in the dermis (2). The location is typically pretibial, but case reports exist of myxedema in other locations. Overall, this case is unusual in that skin findings of myxedema were present in a patient with severe hypothyroidism, and in atypical locations. References: (1) Lause M, Kamboj A, Fernandez Faith E. Dermatologic manifestations of endocrine disorders. Translational Pediatrics. 2017;6(4):300-312. doi:10.21037/tp.2017.09.08. (2) Cao Y, Zhu H, Zheng H, Li J. Myxedema. Lancet Diabetes & Endocrinology. 2014;2(7):600-600.