Background:Hemolytic uremic syndrome (HUS) is characterized by microangiopathic hemolytic anemia, acute renal failure, and thrombocytopenia. It very rarely coexists with acute lymphoblastic leukemia (ALL) emerging before, simultaneously, or after the diagnosis has been made, and management of the patient may be difficult.Case:We present the case of a 7-year-old boy who was diagnosed with HUS and initially managed by hemodialysis (HD). Thereafter, HUS progressed, and neurological findings developed. The patient was treated with eculizumab, agressive blood pressure control, and antiepileptic drugs. At the fifth month of follow-up, the patient was diagnosed with acute B-cell lymphoblastic leukemia with fever, bone pain, hepatosplenomegaly, and pancytopenia. After initiation of ALL treatment, he had no episodes of HUS, despite cessation of eculizumab.Conclusion:In conclusion, eculizumab may be a treatment of choice to prevent further systemic damage in recurrent HUS episodes of patients with borderline changes in the bone marrow until ALL is constantly diagnosed.