Crystalline Nephropathies

Context.-The kidney is a favored site for crystal deposition because of the high concentration of ions and molecules reached at the level of the renal tubules in the course of filtration. This review focuses on crystalline nephropathies in 4 broad categories: (1) dysproteinemia-associated, (2) drug-induced, (3) calcium-containing, and (4) metabolic or genetic. Objective.-To provide a framework for accurate identification of the diverse types of crystals encountered in the kidney in order to formulate an appropriate differential diagnosis and guide additional testing and treatment. Data Sources.-Review of pertinent published literature along with practical experience gained in a high-volume renal pathology laboratory. Conclusions.-Accurate identification of crystals encountered in the kidney is essential in detecting conditions ranging from hematologic malignancy to drug toxicity to metabolic disorders. Detailed clinical-pathologic correlation is needed to accurately diagnose the underlying cause of most crystalline nephropathies. (Arch Pathol Lab Med. 2012; 136: 713-720; doi: 10.5858/arpa.2011-0565-RA)