Almost 17-year-old boy was admitted to hospital in his hometown due to bloody diarrhea. He complained of fatigue. Anemia was observed. Stool culture excluded infectious causes of symptoms. Endoscopy of the lower gastrointestinal tract showed left sided inflammation, highly active, which led to study discontinuation. Sigmoidoscopy gave high suspicion of ulcerative colitis (UC), what was supported by histologic examination. Diagnosis was performed after two weeks from the first symptom. Steroid therapy in dose 40 mg/d was introduced, with good response. However during prednisone dose reduction to 35 mg/d, the symptoms of bloody stools again occurred. Weight loss was observed. The patient was readmitted to hospital in his hometown, where after exclusion of any gastrointestinal infection, the steroid dose was increased to 60 mg/d. Despite the increasing steroid dose, no significant patient’s improvement was observed. After the decision of the parents, the patient was transferred to Our institution. At the time of admission to Our department, the boy complained of fatigue, numerous bloody stools, weight loss of 12 kg was noted. Anemia required blood transfusion. High inflammatory parameters were observed. After obligatory measurement (to exclude any contra-incidence to ciclosporin (CsA) therapy) as magnesium level, kidney assessment with blood pressure evaluation, intra venous CsA was adjusted with conversion to oral intake after good patient reaction. After determination of right dose by proper CsA level in the blood, the patient was discharged to home. Azathioprine (AZA) therapy has been enabled with further steroid dose reduction. Control ambulatory visit showed sustained anemia, but the patient did not complain about any gastrointestinal symptoms, he reported only 2 stools a day. Only lack of weight gain was observed. The dose of ciclosporin was adjusted to the blood level, meanwhile steroids were discontinued. 2 weeks after control visit exacerbation reoccurred. Patient was admitted to Our department. Exclusion of infectious cause was done. The patient had surgical consultation. Patient and parents refused 3 line – surgical therapy and asked for other pharmacological option. After mandatory measurements (RTG, Quantiferon assessment, viral infection exclusion (such as HBV, HCV, HIV)) infliximab (IFX) therapy was introduced. Symptoms of UC were reduced for few days after first IFX dose, nevertheless at other days severe UC signs reappeared. Patient required several blood transfusion. The second IFX dose gave relief of symptoms only for 3 weeks, thus the third IFX dose was adjusted 5 weeks from the first dose. During the third dose of IFX infusion, an allergic reaction was observed. The patient presented face redness with short of breath. The infusion was stopped for 30 minutes, and re-adjusted without any disturbing symptoms. In the following days, improvement of the patient’s condition was observed. The patient achieved clinical remission. Due to severe UC type, further IFX therapy was planned at 4-weeks intervals, with additional antihistamine premedication. The boy had infliximab level measurement before adjustment of the fourth IFX dose (4 weeks after 3^rd dose). Level was in proper range – 5.2 ug/mL. The patient continued IFX therapy performed with 4-weeks interval between doses until he was 18 years old. No AE was reported, neither during IFX infusion or at time between the doses. During all maintenance IFX therapy the boy presented clinical remission.