Idiopathic glomerulopathy in a young ICR mouse.

Idiopathic glomerulopathy of the kidneys was found in a female CRJ: CD-1 (ICR) mouse which died at the age of 33 days. The glomerular lesions were characterized by hyalinization of the glomeruli. There was thickening of the glomerular capillary walls and enlargement of the mesangial areas due to deposits of PAS-positive hyaline material. The hyaline material was distinguished from amyloid, fibrin, acid mucopolysaccharide and immunoglobulins by histochemical and immunohistochemical methods. The basement membrane of the glomerular capillaries was partially thickened, double-contoured and discontinuous. Neither cellular proliferation nor inflammatory cell infiltration was observed in the glomeruli. Ultrastructurally, low electron-dense, amorphous deposits were present in the subendothelial regions and basement membrane of the glomerular capillaries as well as in the mesangium. Atrophy of haemopoietic organs was accompanied by the above lesions.