Mesangial deposits of IgA, diffuse in all glomeruli, have been found in the last 15 years in a great number of diseases, characterized by changes in mucosal surfaces, associated with hyperproduction and/or impaired removal of IgA. The idiopathic type of IgA mesangial nephropathy, first described by Berger and Hinglais in 1968 [1], has only recently attracted the attention of nephrologists, since it is becoming evident that it is the most frequent primary glomerular disease in many countries throughout the world and that it can have a progressive course, leading over variable periods to end-stage renal failure. Two main reasons can explain why this disease has long been neglected:(1) its diagnosis is based on immunohistological examination which became an accepted routine in the majority of institutions only at the end of the 60s;(2) the disease is characterized in more than half of patients by almost no clinical symptoms, so that biopsy is considered unnecessary by many nephrologists.