Idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome is defined by the combination of massive proteinuria, hypoalbuminaemia, hyperlipidaemia, and oedema, and of non-specific histological abnormalities of the glomeruli. Light microscopy may disclose minimal change disease, diffuse mesangial proliferation, or focal segmental glomerular sclerosis (FSGS). The two main causes of idiopathic nephrotic syndrome are characterized histologically. On electron microscopy the glomerular capillaries show a fusion of visceral epithelial cell (podocyte) foot processes and with the exception of some variants no significant deposits of immunoglobulins or complement by immunofluorescence. In a majority of children only minimal changes are seen on light microscopy. These children are referred to as having ‘minimal change disease’. In adults with idiopathic nephrotic syndrome, lesions of FSGS are more frequent.