DIAGNOSIS
Intra- and/or periarticular calcifications with or without erosive, de- structive, or hypertrophic changes may be seen on radiographs (Fig. 327- 3). These should be distinguished from the linear calcifications typical of CPPD deposition disease.
Definitive diagnosis of apatite arthropathy depends on identification of crystals from synovial fluid or tissue (Fig. 327-3). Individual crystals, which generally contain mostly carbonate substituted apatite, are very small and can be seen only by electron microscopy. Clumps of crystals may appear as 1- to 20-um shiny intra- or extracellular non-birefringent globules or ag -gregates that stain purplish with Wright's stain and bright red with alizarin red S. Absolute identification depends on electron microscopy with ener-gy-dispersive elemental analysis,X-ray diffraction, or infrared spectroscopy, but these are usually not required in clinical diagnosis.