Additional blood tests also showed the following results: thrombocytopenia and microangiopathic hemolytic anemia (MAHA; Table 3), SCr 200 μmol/L (eGFR 25 mL/min/1.73 m2), complement component 3 (C3), C4 and ADAMTS13 activity normal, absence of monoclonal (M) spike by serum and urine electrophoresis, anti-nuclear antibodies or extractable nuclear antigens below threshold, and human immunodeficiency virus negative. The gene discussed is C3; the disease is congenital thrombotic thrombocytopenic purpura.