Severe dengue in an adolescent with graves’ disease: a case report

Background Dengue fever is a mosquito-borne viral disease with clinical manifestations ranging from mild febrile to severe disease. Mild cases may present with fever only, whereas severe cases can progress to life-threatening hemorrhage or shock. The coexistence of severe dengue and Graves’ disease in adolescents is rarely reported. Because the two conditions may share clinical manifestations, their coexistence can complicate diagnosis and management. Case presentation We report the case of a 17-year-old female adolescent with severe dengue and preexisting Graves’ disease. The patient had an 8-year history of preexisting Graves’ disease with hyperthyroidism. In June 2025, she traveled to Yunnan Province and reported mosquito bites. In July, the patient travelled to Haikou. One week later, she developed acute nausea, vomiting, diarrhea, and persistent fever. The patient presented to a local hospital on July 15, 2025. Laboratory testing was positive for nonstructural protein 1 antigen and viral nucleic acid, confirming dengue virus infection. Serum complete blood counts showed progressive leukopenia and thrombocytopenia. Endocrinological assessment revealed a suppressed thyroid-stimulating hormone level, elevated free thyroid hormone levels, positive thyroid antibodies, and markedly elevated thyroid peroxidase antibodies (>1000 IU/mL). These findings were consistent with severe dengue, active Graves’ disease, and Hashimoto's thyroiditis. The patient received comprehensive supportive care, including continuous hemodynamic monitoring, gastric mucosal protection, antipyretic therapy, cautious fluid resuscitation, and careful management of the electrolyte and acid-base balance. Methimazole was administered to control thyrotoxicosis. Her clinical condition gradually improved, and she was discharged in stable condition with endocrinology follow-up arranged.