Case Presentation: Hypereosinophilia (HE) is an abnormality noted on complete blood count that can have a myriad of causes. Identification of associated eosinophilia-related organ damage is important in the workup and treatment of this condition. Recognition requires a high degree of clinical suspicion from providers. We present a case of HE with end-organ damage that was recognized and treated promptly. A 75-year-old woman with no past medical history presented to the emergency department for altered mentation. She returned from Puerto Rico, where she had lived for 2 years, the day prior and rapidly became unresponsive and encephalopathic. Work up revealed leukocytosis, hypereosinophilia (AEC 3400, 22%), and lymphadenopathy above and below the diaphragm on CT scan. Repeated troponins were significantly elevated, but unchanging, without ischemic EKG changes. MRI demonstrated multifocal cerebral embolic infarcts. Transthoracic and transesophageal echocardiograms were without intracardiac or valvular pathology. Lower extremity ultrasound discovered a deep venous thromboembolism. Infectious causes of HE were ruled out. A cardiac MRI was suggestive of eosinophilic myocarditis. Cardiac biopsy was not pursued after a discussion with the patient’s family. A bone marrow biopsy demonstrated chronic lymphocytic leukemia (CLL; 10% involvement) with eosinophilic hyperplasia (41%); eosinophils showed normal maturation, and genetic studies were negative (myeloid NGS studies pending). She was diagnosed with HE-related myocarditis and hypercoagulability. Her presentation was suggestive of idiopathic hypereosinophilic syndrome (HES) with incidentally noted CLL, but a CLL-related secondary eosinophilia cannot entirely be excluded. She was started on methylprednisolone, and the next day the eosinophil count had normalized. She was initiated on a steroid taper. After a prolonged hospital stay, her mental status slowly improved, though not back to her baseline. She was discharged to a skilled nursing facility for rehabilitation.
Discussion: HE is defined as an absolute eosinophil count greater than 1500 x 109/L (total WBC x % eosinophils). The etiology of HE can be classified into hereditary, primary, secondary, and idiopathic. Primary causes include myeloid neoplasms, tyrosine kinase fusion genes, or chronic eosinophilic leukemia. Secondary causes are infection, autoimmunity, allergic or hypersensitivity responses, and paraneoplastic phenomena. The work up and treatment of HE are directed at controlling the underlying cause and minimizing organ dysfunction from eosinophil tissue infiltration. HES is identified by persistent idiopathic HE associated with organ damage. Commonly affected organs include skin, lungs, and gastrointestinal tract, although any organ can be involved. Eosinophilic cardiomyopathy is a severe complication associated with a high case fatality rate if not treated promptly. Once recognized, patients should immediately start glucocorticoid therapy to reduce eosinophilia and limit organ damage.
Conclusions: HES is a rare, but life-threatening condition. It requires a high degree of clinical suspicion to diagnose and should be suspected in patients presenting with peripheral eosinophilia and evidence of end organ damage. Recognition of the condition by hospitalists and critical care providers is important as it must be treated promptly with steroids to reduce HE, and appropriate work up should be pursued to determine the etiology.