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Vancomycin is a widely used antibiotic known as a nephrotoxic agent causing AKI mainly through acute tubular necrosis (ATN) or tubulointerstitial nephritis (TIN), although recently a new mechanism of renal injury has been described: vancomycin associated cast nephropathy. We hereby report a case of this unusual entity.
A 52-year-old male patient with a history of freebase cocaine addiction was admitted to our hospital presenting severe bilateral pneumonia and shock, requiring mechanical ventilation and vasoactive drugs. Vancomycin and piperacillin tazobactam at maximum doses were prescribed on admission, with normal renal function (creatinine 0,72 mg/dl). On the third day he became oliguric and creatinine rose to 4,8 mg/dl, with vancomycin levels at 32 μg/ml, thus starting renal replacement therapy with a diagnosis of sepsis and vancomycin related AKI. Although he recovered urine output after one week, creatinine still elevated (8 mg/dl) and persistent proteinuria (1,47 g/day) prompted us to perform a renal biopsy on day 17. Ultimately the patient condition worsened, developing a refractory shock and dying on day 25.
Renal biopsy revealed extensive tubular necrosis with tubules showing lots of granular and hyaline casts ocluding 40% of the global tubular lumen. Immunofluorescence was negative for IgA, IgG, IgM, C3, C1q and fibrinogen. The patient also presented a normal serum proteinogram with no monoclonal components, normal CPK and calcemia, thus discarding usual causes for this cast nephropathy, such as multiple myeloma or rhabdomyolysis.
Vancomycin associated cast nephropathy seems to be an underdiagnosed entity due to the assumption of ATN as the probable cause for any AKI during vancomycin treatments, thus precluding nephrologists from performing renal biopsies in these cases. An appropriate diagnosis could be of importance because it is a reversible disease with favourable prognosis, mostly when vancomycin is suspended.