Microstructure and Mineral Composition of Dystrophic Calcification Associated with the Idiopathic Inflammatory Myopathies
Naomi Eidelman, A Boyde, A.J. Bushby, P.G.T. Howell, Jirun Sun, F.W. Miller, P Robey, Lisa Rider
Calcified deposits are present in 30% of children with juvenile dermatomyositis (JDM) and less frequently in adult dermatomyositis (DM). This study aimed to determine the microstructure, composition and stiffness of these deposits. Specimens were analyzed with Fourier Transform Infrared microspectroscopy in reflectance mode (FTIR-RM), X-ray diffraction (XRD), X-ray microcomputed tomography (µCT), quantitative backscattered electron (qBSE), nanoindentation and polarized light microscopy (PLM). FTIR-RM showed that some specimens were composed of continuous carbonate apatite containing small amounts of proteins, with mineral to protein ratio higher than in bone. Other specimens contained scattered agglomerates of various sizes with similar composition. µCT confirmed that continuous or fragmented mineralization was present across the whole specimens. XRD revealed that the apatite was more crystallized than in bone and dentin, but less than in enamel. The mineral density (qBSE) was closer to enamel than bone and dentin and so was the stiffness (nanoindentation) in the larger dense patches. Large mineralized areas were typically devoid of collagen; however, collagen was noted in some regions incorporated within the mineral or on the margin (PLM). FTIR-RM maps and qBSE images suggest that the mineral deposited first in a fragmented pattern followed by a wave of mineralization that incorporates these particles. Masses with shorter duration appeared to have islands of mineralization, whereas longstanding deposits were solidly mineralized. Calcium and phosphate, normally present in affected tissues, might have precipitated as carbonate apatite due to local loss of mineralization inhibitors.
, Boyde, A.
, Bushby, A.
, Howell, P.
, Sun, J.
, Miller, F.
, Robey, P.
and Rider, L.
Microstructure and Mineral Composition of Dystrophic Calcification Associated with the Idiopathic Inflammatory Myopathies, Bone and Mineral, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=854140
(Accessed November 29, 2023)