Abstract
Cardiac tamponade as the initial manifestation of Hashimoto's thyroiditis is an exceedingly uncommon occurrence. We present the case of a 36-year-old female who was admitted due to acute respiratory distress. A cardiac ultrasound revealed a severe pericardial effusion with tamponade signs. Subsequently, percutaneous pericardiocentesis was performed, resulting in a swift clinical improvement. Laboratory examinations confirmed severe hypothyroidism associated with Hashimoto's disease. Despite undergoing hormone replacement therapy, histological analysis of the pericardium revealed a chronic inflammation process. A follow-up cardiac ultrasound conducted six months later indicated the presence of a well-tolerated chronic pericardial effusion. In conclusion, clinicians should consider hypothyroidism as a potential cause when cardiac tamponade is observed, particularly in the absence of tachycardia. The prognosis is generally favorable with hormone replacement therapy, but regular ultrasound monitoring should be maintained until the patient achieves a euthyroid state.