Case Report: A 58-year-old female patient was referred to the hematology clinic in July for examination after leukocytosis was detected in her tests. She has a known history of CKD, Type 2 DM, HT, hyperlipidemia. The patient's general condition is good, and she had a complaint of numbness in her hands. First 1.5 months ago, numbness in her right hand up to the wrist began,especially severe in the first 3 fingers The same complaints started in her left hand 1 month ago. Physical examination findings were within normal limits. On sensory examination, there was hypoesthesia in the first 3 fingers of both hands, especially on the right. In the blood tests performed at the time of admission, leukocytes were 34.440μL, neutrophils 8.840μL, eosinophils 20.540μL, absolute lymphocyte count 3.890μL, monocytes 1.080 μL, hemoglobin 12 g/dL, platelets 348.000 μL, creatinine 1.07 mg/d/L, CRP: 56.6 mg/dL, sedimentation - 10 mm/h were measured. The patient has had borderline eosinophilia (1510μL) since 2022. Flow cytometry was performed on peripheral blood. 11% lymphoid series and 89% myeloid series cells were seen. No abnormality was observed in the lymphoid series. A slight regression in maturation was seen in myeloid series cells and an increase in eosinophilic series cells. Blast ratio was detected as negative. ECHO findings were normal. No pathology was observed in the lung. Diagnostic bone marrow biopsy was performed.EMG revealed sensorimotor demyelination with block at the wrist levelin the right median and neuropathy with secondary axonal damage. It was evaluated as CTS. After the biopsy, corticosteroid treatment was startedOn the 2nd day of treatment, the patient's eosinophil count was 350μLShe was discharged with oral steroid treatment and discharged with oral steroid.In the control eosinophils decreased to2160 μL. In the pathology report of biopsy, hypereosinophilic syndrome was considered.No diagnostic findings were detected in favor of neoplastic/clonal eosinophil expansion