The significance of pure diffuse mesangial proliferation in idiopathic nephrotic syndrome.

The prognostic significance of the finding of diffuse mesangial proliferation (DMP) in patients presenting with idiopathic nephrotic syndrome (INS) has not been well established. The clinical course, therapeutic response and final outcome of 38 patients in whom renal biopsy showed DMP are reported. They have been subdivided into 2 groups according to the absence (18 patients: group I) or presence (20 patients: group II) of superimposed lesions of focal and segmental sclerosis and/or hyalinosis (FSS/H). Clinical presentation was similar in both groups although patients in group I were less severely affected. Non of the patients of group II responded to corticosteroids, whereas in group I 2/16 responded and 2 infants remitted without treatment. At the latest assessment, 5/18 patients in group I and 10/20 in group II had progressed to terminal renal failure or had impaired renal function. Five patients in group I and 3 in group II were in clinical remission. Eight of 11 repeat biopsies performed in patients of group I showed the development of FSS/H. Thus patients with DMP seem prone to develop lesions of FSS/H. Their course if often worse than that of minimal change with FSS/H since 7 of the 10 patients who developed renal failure did so within 3 years of onset. The finding of DMP in a patient with idiopathic nephrotic syndrome is usually but not invariably an ominous feature.