[Methotrexate induced crystalline nephropathy: A rare histological finding on renal biopsy].

Drug-induced crystalline nephropathies are secondary to abnormal accumulation of crystals leading to parenchymal renal injuries. Methotrexate, used to treat a wide range of malignancies, is one of the various drugs accountable in this particular condition. We report a case of acute renal injury during the course of high-dose methotrexate therapy in a patient presenting primary cerebral diffuse large B-cell lymphoma. Interestingly, the kidney biopsy revealed intratubular methotrexate crystal formations. We also summarize the distinctive characteristics of main crystalline nephropathies in order to guide pathologists toward the many types of crystals encountered on renal biopsy.