Blood examinations revealed hemolytic-uremic syndrome (HUS), with macrocytic anemia (hemoglobin 9.0 g/dl, normal values [nv] 10.7–13.4; MCV 86.1 ft., nv 75–85), thrombocytopenia (platelets count 40000 × 103; nv 210–590), elevated LDH (up to 3000 IU/L, nv 192–321) and creatinine (from 0.56 to 1.2 mg/dl, nv 0.2–0.43), low albumin rate (2.6 g/dl, nv 3.5–4.5), very low haptoglobin levels (< 7.5 mg/dl; nv 30–200), negative Coombs test (both direct and indirect), proteinuria and hematuria; complement serum levels resulted low (C3 69 mg/dl, nv 90–180; C4 9 mg/dl, nv 18–55). The gene discussed is C4A; the disease is hemolytic-uremic syndrome.