Subjects with known or suspected forms of sclerosing glomerular or chronic, fibrosing tubulointerstitial kidney diseases will undergo routine medical evaluation, laboratory testing, imaging procedures and kidney biopsies as medically indicated. Selected subjects will be invited to provide informed consent to undergo a kidney biopsy for research purposes. Blood, urine, and tissue samples will be evaluated both for standard diagnostic purposes and for research purposes using specialized molecular methods that may provide insights into specific disease pathogenesis. Subjects may elect to receive the results of their kidney disease evaluation, NIH treatment recommendations, and return to the care of their referring physicians. Other subjects may be treated with either conventional or approved agents, or (with separate consent) with a novel combination of conventional therapies (rituximab and cyclosporine) as part of pilot studies that would involve long-term follow-up care at the NIH.