The Significance of Calcium Phosphate Crystals in the Synovial Fluid of Arthritic Patients: The "Pseudogout Syndrome"

Abstract

In the course of examining over 200 synovial fluid specimens by polarized light microscopy, fluids from 7 patients were found to contain significant amounts of an as yet unidentified crystalline material. In 5 instances sufficient material was available for further study, including infrared spectrophotometry, emission spectroscopy, X-ray flourescence, and X-ray diffraction by the powder method. By these methods, the crystals were shown to be virtually identical, and a tentative identification as calcium pyrophosphate was made. The utilization of X-ray diffraction proved to be especially useful in demonstrating the crystallographic identity of the 5 specimens studied. Further study by X-ray diffraction demonstrated that the crystals were distinct from both tophaceous material and from the apatite constituent of an osteo-chondroma. The applicability of this method in investigating the crystalline state in biological systems is briefly reviewed.