Structural and chemical characterization of a cutaneous calcification

Dynamic thermogravimetry, X-ray diffraction, spectroscopic and chemical analyses have been carried out on the cutaneous calcifications present in a case of Porphyria cutanea tarda. The inorganic deposits are constituted by a poor crystalline B carbonated apatite characterized by an almost stoichiometric Ca/P molar ratio, a low magnesium relative content and a high thermal stability. The inorganic crystallites grow in the cutaneous calcification without any preferential orientation in the tissue where the collagen fibrils are isotropically distributed. The results reveal that the cutaneous calcifications display a close similarity with the inorganic deposits isolated from atheromatous plaques of aorta and calcified mitral valves.