Nephrocalcinosis in a Transplanted Kidney: A New Sign of Chronic Tacrolimus Nephrotoxicity

Calcineurin inhibitors are potent immunosuppressive drugs in solid-organ transplantation and multiple autoimmune diseases. Their use is associated with the acute impairment of glomerular filtration and chronic interstitial fibrosis. The latter is mediated by the accumulation of matrix proteins. In this case report, we present a kidney transplant patient with chronic and progressive allograft failure that was associated with nephrocalcinosis. He did not have hypercalcemic-hypercalciuric states such as hyperparathyroidism, sarcoidosis, and hyper-vitaminosis D; normocalcemic-hypercalciuric states such as distal renal tubular acidosis, medullary sponge kidney, excessive use of high-dose loop diuretics, and beta-thalassemia; hyperphosphaturic conditions; and hyperoxaluria. Moreover, his calcifications were limited to the transplanted kidney and spared the native kidneys and extrarenal tissues, and his renal function had improved and stabilized for 6 months after discontinuation of prolonged-release tacrolimus (Advagraf), indicating a cause and an effect phenomenon. Nephrocalcinosis was suspected after ultrasonography and confirmed by computed tomography scanning. Hence, allograft nephrocalcinosis may indicate chronic tacrolimus nephrotoxicity.