Idiopathic renal lipofuscinosis. Two cases.

Two cases of dark-brown or black discoloration of the human kidney are described and the condition compared with two previously reported cases. The abnormal colour is due to a deposition of brown pigment in the epithelium of the proximal tubules. The staining properties and histochemistry of the pigment granules seem to allow identification of the pigment as a lipofuscin. In one case the patient is still alive and the condition does not seeto have had any harmful effect on kidney function. This abnormality seems to be extremely rare. It is perhaps analogous to the disease, “Black Kidney” in cattle.