Case Presentation: A 62-year-old man with type 2 diabetes was hospitalized with a two-week history of fatigue, sore throat, diarrhea, and 18-pound weight loss. In the ED, he was hypotensive and tachycardic, which improved with IV fluids. Physical exam was significant for bilateral posterior cervical lymphadenopathy and splenomegaly. Labs showed leukocytosis (25.8K) with 18.2% lymphocytic predominance, transaminitis (AST/ALT 224/358 Alk phos 316) and new onset hyperthyroidism (TSH <0.01, Free T4 2.2 and Total T3 113). Blood smear showed atypical lymphocytosis. CT showed retroperitoneal lymphadenopathy and mild splenomegaly. Thyroid ultrasound was negative for nodular disease. Peripheral blood flow cytometry was not consistent with malignancy. The patient was found to have positive Epstein-Barr Virus (EBV) IgM and heterophile antibodies. He was diagnosed with infectious mononucleosis with associated acute viral thyroiditis. He received supportive treatment with IV fluids and pain control. Anti-thyroid medications were avoided given transaminitis and resolution of tachycardia. His symptoms and lab tests slowly improved, and he was discharged. The patient was found to have normal thyroid function tests as an outpatient 2 weeks later; however, his TSH receptor antibody and thyroid stimulating antibodies resulted as positive. He is pending further evaluation in the outpatient clinic.
Discussion: EBV is a human herpesvirus that usually causes a transient viral syndrome. However, EBV can increase the risk of malignancy through the activation of B lymphocytes in the long term. Our patient was found to have new-onset hyperthyroidism in the setting of acute EBV infection, suggesting that EBV may contribute to the development of autoimmune thyroid disease. Viral infections have been associated with a transient thyroiditis. However, few cases have resulted in the development of potentially permanent thyroid autoantibodies, leading to either symptomatic hypo- or hyperthyroidism. Studies of thyroid tissue specimens in patients with Graves and Hashimoto’s disease have shown significantly elevated levels of EBV RNA in thyroid follicular cells and infiltrating lymphocytes. This suggests that the initiation of autoimmune thyroiditis may begin with the recruitment of inflammatory lymphocytes and the production of inflammatory cytokines. This case illustrates the development of autoimmune hyperthyroidism in real-time and lends support to the theory that activated B lymphocytes may not only lead to malignancy but also hormonal imbalances.Our patient’s superimposed thyroiditis may explain the severity of some of his symptoms such as severe diarrhea that led to hypotension and tachycardia and his 18-lb weight loss in two weeks. However, thionamides, which would normally be indicated in symptomatic hyperthyroidism, were avoided given his transaminitis. Supportive therapy was sufficient.
Conclusions: Infectious agents such as EBV may contribute to the development of autoimmune thyroid disease, which may cloud the presentation of a viral syndrome. Thus, it is important for hospitalists to test for thyroid function in patients with infectious mononucleosis and convey the importance of monitoring for autoimmune thyroid disease to patients’ primary care providers.