Massive pericardial effusion in a patient with Hashimoto's thyroiditis: histological examination of underlying cardiomyopathy.

An unusual case of a hypothyroid patient with huge pericardial effusion due to Hashimoto's thyroiditis is reported. Cardiac tamponade occurred during admission. Eight hundred milliliters of pericardial effusion was withdrawn by pericardiocentesis. Even after successful replacement of thyroid hormone, she had recurrent effusion two years later. Refractory pericardial effusion is a rare complication in treated hypothyroid patients. Underlying cardiomyopathy was presented with hemodynamic and histological examinations.