Crystal Deposition Diseases

This exhibit is intended to portray the central role that crystals play in two common "metabolic" arthritides, classic gout and chondrocalcinosis articularis1(pseudogout syndrome2). In this discussion we will reverse the usual order of presentation and cover the clinical features last. Diagnosis by Crystal Identification The differential diagnosis of arthritis is greatly aided by the gross and microscopic examination of synovial fluid (synovianalysis3). Crystals of sodium urate and calcium pyrophosphate are best seen in "wet" preparations of freshly aspirated synovial fluid. A drop of fluid is applied to a clean glass slide and overlaidimmediatelywith a clean coverslip, the edges of which are sealedimmediatelywith clear fingernail polish. Dried smears of fluid are difficult to inspect; centrifugation of the fluid before examination isnotrecommended. Compensated polarized light and phase contrast microscopy (magnification × 1,250) are simultaneously used in our laboratory; sodium urate crystals show