BACKGROUND
Idiopathic hypereosinophilic syndrome (I-HES) is a rare disease diagnosed as absolute eosinophil count >1500 cells/µl and end-organ involvement attributable to tissue eosinophilia with no secondary cause of underlying eosinophilia. The mean age of presentation for I-HES is 44 years. The skin, lungs, and gastrointestinal (GI) system are most common sites of presenting manifestations, including fatigue, cough, dyspnea, myalgias, angioedema, rash, fever, nausea, and diarrhea. Although cardiac and neurologic symptoms are less common at presentation, they can be life-threatening.
CASE REPORT
We report the case of an 85-year-old man who presented with fever, malaise, and loss of appetite for 3 weeks, followed by dyspnea and dry cough for 2 weeks. His absolute eosinophil count was 9000 cells/µl, which was not responding to empirical antibiotic therapy, with worsening of symptoms, suggesting a non-infective origin. He was then extensively evaluated to establish underlying an etiology for specific treatment, which was negative for common causes like atypical infections, malignancy, and autoimmune disorders. He was then started on corticosteroid therapy to overcome an exaggerated immune response and reduce inflammation-related injury, to which he responded well. On follow-up, hypereosinophilia was fully cured, with reversal of end-organ involvement including myocarditis and pneumonitis.
CONCLUSIONS
This report shows that idiopathic HES can present with various clinical features and that accurate diagnosis, excluding known causes of eosinophilia, and early management are essential to prevent long-term organ damage. Our patient responded to prompt treatment with high-dose corticosteroids.

Keywords: Geriatrics; Multimodal Imaging; Hypereosinophilic Syndrome; Pulmonary Eosinophilia; Myocarditis