Identification of Calcium Hydrogen Phosphate Dihydrate Crystals in Human Fibrocartilage

Abstract

RECENTLY, we identified microcrystalline calcium pyro-phosphate dihydrate in certain pathological human synovial fluids¹. Roentgenograms of the involved joints showed calcifications in cartilaginous structures; the clinical picture was distinctive enough to suggest a specific syndrome, which we named ‘pseudogout’². In two cases multiple cartilages were examined post mortem and most contained localized deposits of these crystals³. The interplanar spacings found on X-ray diffraction powder pattern are virtually identical with those reported for calcium pyrophosphate dihydrate prepared by Brown et al.⁴ by hydrolytic degradation of calcium polymetaphosphate gel. Monoclinic and triclinic dimorphs have been identified by these same workers⁵. In human material, the triclinic dimorph predominates although interplanar spacings indicative of the monoclinic form are detected frequently⁶.