Two siblings born from consanguineous parents experienced infantile nephrotic syndrome with ocular and neurological abnormalities; the boy also had a micropenis; both patients died before age 1 year. An initial renal biopsy followed by a two-step binephrectomy allowed good histological assessment of disease progression in one patient. The progression of the lesions was characterized by mesangial involvement, then an extensive extracapillary proliferation and tubular dilatations with a high mitotic activity of the epithelium and nuclei of unequal size. The main features involved major ultrastructural changes of the glomerular basement membrane. These two patients may represent a new disease entity or a severe form of diffuse mesangial sclerosis, with autosomal recessive inheritance.