The pathology of lithium induced nephropathy: a case report and review, with emphasis on the demonstration of mast cells.

Lithium is a psychotropic agent which is widely employed in the psychiatric practice throughout the world. The therapeutic index of lithium is low and an acute intoxication may appear, which may lead to death or a permanent disability. A frequent side effect of lithium is renal toxicity. The collecting tubules have been identified as the site of action of lithium, due to the down regulation of Acquaporin-2. The mast cells have been associated with a wide range of human renal diseases. They have been documented to be associated with interstitial fibrosis and an impaired renal function. We are reporting a case of a 42 year old male who was admitted with a history of an altered sensorium of short duration. He had bipolar disorder and was on lithium. Investigations revealed a severely compromised renal function. The patient's condition worsened and he expired. A necropsy was performed. The kidneys and the lungs were subjected to a histopathological examination. The kidneys showed a significant Chronic Tubulointerstitial Nephropathy [CTIN] and a considerable glomerular pathology. Toludine blue [1%] staining demonstrated mast cells in the interstitium and the connective tissue of the renal pelvis. This appears to be the first time that mast cells were demonstrated in a case of lithium induced nephropathy in humans. It may be hypothesized that mast cells may possibly play a role in lithium induced nephropathy as a concurrent mechanism.