Electron microscopy and microanalysis of a subcutaneous heterotopic calcification

This paper reports the study of a subcutaneous heterotopic calcification from a patient with Thibierge-Weissenbach's syndrome, a type of creeping scleroderma included in the CRST syndrome. These local deposits, whose origin is still unknown, are commonly considered to be a classic apatite phase. Using SEM, high resolution TEM, electron diffraction, infrared spectrometry, and SEM and TEM microanalysis, it is demonstrated that this material is highly heterogeneous and appears in a nonstoichiometric, carbonated, calcium ion-deficient apatitic solid phase. Our study shows the coexistence of dense globules presenting an ill-organized, more or less amorphous phase (ACP) or microcrystalline (OCP, beta tricalcium phosphate), with scattered apatite crystals, and of interglobular apatite crystals with a good cristallinity.