Laboratory and immunological evaluation revealed positive cryoglobulins, markedly elevated rheumatoid factor (1058 UI/mL) and IgM levels (715 mg/dL), reduced complement levels (C3, C4), normocytic normochromic anemia, microscopic hematuria, and elevated ALT (156 U/L), AST (142 U/L), total bilirubin (1.4 mg/dL), and INR (1.6), suggestive of hepatic inflammatory activity. The gene discussed is C3; the disease is anemia.