Eleven of these patients underwent kidney biopsies, revealing acute rejection in 7 cases, thrombotic microangiopathy secondary to CNI toxicity in 1 patient (i.e., there was no mesangial hypercellularity or endocapillary proliferation, no deposition of immunoglobulin or C3, with exclusively arteriolar lesions displaying fibrin deposits and severe hyalinosis), chronic allograft nephropathy in 2, and acute tubular necrosis in 1 patient. The gene discussed is C3; the disease is thrombotic microangiopathy.