Polyarthritis as the Initial Presentation of Hyper Eosinophilic Syndrome.

Hyper eosinophilic syndrome (HES) is a rare condition with a potential for morbidity and mortality, if left untreated. Therefore, it is important to highlight it, as often these cases are misdiagnosed and mismanaged, specially when presenting with an atypical initial presentation. This case report describes an unusual initial clinical presentation of HES. Patient was a 75-year lady presenting to Rheumatology Clinic with short duration of fever and polyarthritis. Joint aspiration showed purulent fluid with a cell count of 61,000/mm3 with predominant neutrophils and eosinophils. Her peripheral blood also showed a high white blood cell (WBC) count (80,700/mm3 with 73% eosinophils). Her workup for eosinophilic leukemia was negative, so a diagnosis of HES was made. She was initiated on corticosteroids and hydroxycarbamide as first-line therapy. Unfortunately, the patient was unresponsive to steroids with her WBC count rising to 130,000/mm3 and her clinical course was complicated by cardiac failure and peripheral neuropathy. Improvement in arthritis and peripheral eosinophilia was noted after she was given imatinib and stabilised clinically.