Idiopathic hypereosinophilic syndrome presenting as cardiac tamponade and multiorgan dysfunction.

Idiopathic hypereosinophilic syndrome is characterised by the overproduction of eosinophils with tissue infiltration, leading to multiorgan dysfunction. Its heterogenous presentation makes the diagnosis challenging and easy to miss. A woman in her 70s was admitted with chest pain and shortness of breath. Diagnostic testing showed elevated cardiac enzymes, an ejection fraction of 45% and pericardial effusion. Pericardiocentesis helped her symptoms significantly. Cardiac catheterisation revealed patent coronary arteries. She was diagnosed with myopericarditis and discharged on non-steroidal anti-inflammatory drugs. She returned the following week with worsening chest pain, dyspnoea and diarrhoea. Chest imaging showed bilateral infiltrates. Diagnostic testing showed eosinophilic predominance in peripheral blood (59%), pericardial fluid (37%) and bronchoalveolar lavage (31%). After a negative infectious workup, she was started on glucocorticoids and responded favourably. She was discharged on steroids. Mepolizumab was initiated outpatient, and steroids were discontinued. Mepolizumab was discontinued after 2 years while monitoring her symptoms and eosinophil counts.