The atypical hemolytic uremic syndrome (aHUS) is an ultra-rare disease with a genetically determined dysregulation of the alternative complement pathway, which leads to the development of thrombotic microangiopathy. The application of the targeted therapy in Russia has changed the natural course of the disease since 2012: from death of a patient to achieving a long-term remission of the aHUS. The authors report the clinical case of the aHUS associated with a heterozygous mutation in CFH gene c.2850G>T (p.Gln950His) in a 2 years and 2 months old pediatric patient. The difficulty in diagnosing of the aHUS was the lack of specific laboratory criteria confirming the diagnosis as well as the presence of a diarrheal prodrome at the onset. The diagnosis has been made on the basis of the development of microangiopathic hemolytic anemia, thrombocytopenia, acute kidney injury and the exclusion of other forms of thrombotic microangiopathy. The treatment of the patient in accordance with the clinical guidelines for the management of patients with this nosology proved to be effective and led to a stable remission of the aHUS, which also confirmed the correctness of the diagnosis. The described clinical case observation is of interest to pediatrician physicians and nephrologists. The important factors in the management of such patients are the timely diagnosis of the aHUS along with the initiation of complement-inhibiting Eculizumab therapy.