NEPHROTIC SYNDROME IN THE 1ST YEAR OF LIFE

Among the various primary conditions which may be associated with a nephrotic syndrome at birth or within the 1st year of life, the best known is the congenital nephrotic syndrome of finnish type (CNF) characterized by irregular pseudocystic dilatation of proximal tubules. This disease, very frequent in Finland, is often familial with an autosomal recessive mode of inheritance. Patients are steroid resistant, but the cause of death is usually not uraemia but infection or severe diarrhoea with electrolyte imbalance. The second condition is idiopathic nephrosis including minimal change disease, diffuse mesangial proliferation and focal segmental glomerular sclerosis. As opposed to CNF, infants with ''early onset nephrosis'' may respond to steroid therapy as older children do and may even recover. However, there are no histopathological criteria which allow the certain differentiation of idiopathic nephrosis from CNF. The third condition is diffuse mesangial sclerosis (DMS), a clinicopathological entity which can occur as an isolated finding or be associated with male pseudohermaphroditism and/or Wilms' tumour (Drash syndrome). From a morphological point of view, DMS is easy to differentiate from CNF because of the characteristic pattern of involvement of the glomeruli. From a clinical point of view, the nephropathy, almost always characterized by a nephrotic syndrome, has two distinct features: it is most often diagnosed in the first 2 years of life and it progresses rapidly to end-stage renal failure, which usually occurs before the age of 3 years. The clinical findings in 36 patients with DMS are presented. The nephropathy was isolated in 22 infants and associated with male pseudohermaphroditism and/or Wilms' tumour in 14. The early onset of the nephropathy, its familial incidence and its association with Drash syndrome suggests an antenatal dysgenetic process. Recent studies indicate a direct role of WT1 (a Wilms' tumour gene) in the aetiology of Drash syndrome, and mutations of this gene have been found in 3 patients herein reported. It remains to be demonstrated whether or not the WT1 gene is also altered in patients with isolated DMS.