Background: Idiopathic hypereosinophilic syndrome is characterized by persistent hypereosinophilia with end organ damage and no definite underlying cause. It has been recognized that eosinophils can induce varying degrees of neural damage. There are only a few reports in the literature regarding CSF by eosinophils, and the relationship between hypereosinophilic syndrome and eosinophilic leukemia remains unclear.
Case description: We report a case of IHS with CSF infiltration by immature eosinophils and significant subdural effusion with underlying brain parenchyma compression. He was treated by inserting a subdural-peritoneal shunt with improvement. Respiratory distress and pulmonary infiltration with eosinophils developed. Imatinib mesylate (Gleevec) was added with improvement, and subsequent CSF study showed normalization of CSF cytology analysis. However, re-collection of subdural fluid developed later and resulted in consciousness disturbance, and the patient died thereafter.
Conclusion: Idiopathic hypereosinophilic syndrome remains a serious condition with a poor prognosis for most patients. Cerebrospinal fluid infiltration by immature eosinophils is a rare condition in IHS and may lead to poor prognosis, as observed in this patient, despite improved medical management (steroid and imatinib mesylate) and adequate surgical shunting for the subdural effusion.