Supportive Versus Immunosuppressive Therapy for the Treatment Of Progressive IgA Nephropathy

Inclusion Criteria: * Male or female patients from 18-70 years with histologically proven primary IgAN with typical mesangioproliferative features. Diagnosis has to be made by a neuropathologist. * Proteinuria above 0.75 g/day within 12 weeks prior to or at the first visit in the run-in phase (month -6)and presence of at least one further risk factor for the development of end stage renal disease 1. arterial hypertension, defined as ambulatory blood pressure \>140/90 mm Hg or the use of antihypertensive medication or 2. impaired renal function, defined as creatinine clearance or estimated GFR \<90 ml/min. Exclusion Criteria: * Known allergy or intolerance to study medication (except in case of ACE-inhibitor, in which case a change to an angiotensin receptor blocker is possible). * Women who are pregnant or breastfeeding and women without sufficient contraception. * Any prior immunosuppressive therapy. * Variants of primary IgAN (e.g. rapidly progressive IgAN with crescents in \>50% of glomeruli or minimal change GN with glomerular IgA deposits). * Significant liver dysfunction (more than three fold increased GPT compared to norm) * Contraindication for immunosuppressive therapy, like * acute or chronic infectious disease incl. hepatitis and HIV positive patients * any malignancy * leukocytopenia, thrombocytopenia or known allergy against prednisolone, cyclophosphamide or azathioprine * active intestinal bleeding, active gastric or duodenal ulcer * Need of permanent immunosuppression, (e.g. transplanted patients, steroid-dependent inflammatory diseases) * Secondary IgAN or diseases associated with glomerular deposits of IgA. * Additional other chronic renal disease. * Creatinine clearance below 30 ml/min (mean of 3 measurements). * Alcohol or drug abuse * Mental condition rendering the subject unable to understand the nature, scope, and possible consequences of the study * Subject unlikely to comply with protocol, e.g., uncooperative attitude, inability to return for follow-up visits, and unlikelihood of completing the study * Participation in a parallel clinical trial or participation in another clinical trial within the last 3 months. * Subjects who are in any state of dependency to the sponsor or the investigators. * Employees of the sponsor or the investigators. * Subjects who have been committed to an institution by legal or regulatory order.