Renal infiltration of peripheral T-cell lymphoma, not otherwise specified, mimicking drug-induced acute interstitial nephritis.

Renal invasion of T-cell lymphoma does not usually occur. The renal infiltration of peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), is rare. Therefore, the detailed pathology, clinical features, and effective therapy of this type of extranodal disease remain uncovered. Here, we report the rare case of acute kidney injury (AKI) caused by the renal infiltration of PTCL-NOS with no evidence of lymphadenopathy and extranodal lesions, except for the kidney. We mistakenly diagnosed our patient with drug-induced acute interstitial nephritis (AIN) at first, because his clinical features were similar to those of drug-induced AIN; however, we reached the correct diagnosis by detecting atypical T-cells in his urine. After the introduction of cyclophosphamide, doxorubicin, vincristine, and prednisone therapy his general condition improved rapidly. When suspecting drug-induced AIN as the cause of AKI, PTCL-NOS should also be recognized as one of the causes, and urine cytology may be useful to noninvasively distinguish between the two diseases.