Abstract
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.