SAT-371 Rapidly Enlarging Goiter in the Setting of TPO >5000

Abstract Disclosure: J. Martone: None. S. Douglas: None. M.M. Kristan: None. Introduction Hashimoto’s disease is an autoimmune disease characterized by the progressive destruction of the thyroid gland leading to hypothyroidism. This typically evolves over many years, however we present a case of rapidly progressive fibrosing type of Hashimoto’s disease with TPO antibody levels >5000 IU/mL. Case ReportA 47-year-old female presented with dyspnea leading to evaluation for possible asthma. During the asthma workup, she was found overnight to have had a rapid enlargement of the anterior neck along with diffuse lymphadenopathy, leukocytosis, and intermittent fevers. The finding of a rapidly growing goiter led to further evaluation to rule out more concerning pathologies, particularly neoplasm. Initial ultrasound revealed a hypoechoic nodule, but one week later, a repeat ultrasound at time of attempted biopsy revealed no discrete nodule. Repeat imaging every 6 months revealed dynamic, rapidly changing parenchyma. However, radiographic features of anaplastic thyroid cancer were notably absent, and random thyroid parenchyma biopsies showed moderate amounts of watery colloid and benign appearing follicular epithelial cells in a honeycomb flat pattern with the absence of Hurthle cells. The pathology report concluded the mass to be a benign colloid nodule. Laboratory studies revealed a TPO antibody of >5000 IU/mL. She experienced progressive hypothyroidism with escalating doses of levothyroxine. After 3 years of symptoms, the patient elected to undergo thyroidectomy with pathology revealing Hashimoto’s disease, fibrosing type. One month post thyroidectomy the TPO levels were measured at 1260 IU/mL. DiscussionThis case highlights an abnormal presentation of Hashimoto’s disease characterized by a rapid enlargement of the thyroid gland and a high antibody titer(TPO>5000 IU/mL). Constitutional symptoms of fever and lymphadenopathy and a clinical picture inconsistent with typical clinical presentations raised concerns for the possible alternative diagnosis of anaplastic thyroid cancer and Reidel’s thyroiditis. In such clinical presentations, biopsy and ultrasound images are necessary to confirm the suspicion of Hashimoto’s disease. Given the clinical improvement seen post-thyroidectomy, consideration for early total thyroidectomy should be made in cases of Hashimoto's disease with elevated TPO titer and rapid disease progression. Presentation: Saturday, July 12, 2025