Background/Purpose: Juvenile Dermatomyositis (JDM) is a systemic vasculopathy, primarily involving the micro vasculature. Soft tissue calcification occurs in 15-30% of cases, and is associated with increased morbidity and mortality. The calcifications develop in conjunction with chronic inflammation, and are often located at pressure points of daily trauma (elbows, buttocks, hands).  In contrast, calcifications of aortic heart valves in non-JDM patients are more common and are associated with interrelated factors such as hypertension, hyperlipidemia, obesity, smoking and diabetes.  The purpose of this investigation was to compare the composition and structure of the calcific deposits obtained from children with JDM with those in removed aortic valves.

Methods: Five children (2 boys, 3 girls) previously reported (Arthritis Rheum 54:10 2006, 3345-3350) with definite JDM, had a mean age of JDM onset, 3.3 years ± 1.9 years. They had sustained persistent cutaneous inflammation for 81.3 ± 58.7 months, and donated calcium deposits, after obtaining informed consent. The calcifications, removed by surgery, were a focus of constant pain and contributed to decreased range of motion.  Fresh, calcified aortic heart valves were obtained at cardiovascular surgery, after obtaining informed consent, from 5 White adult donors without JDM (age range 43-85, mean age= 69.2 years), two were women, with severe aortic stenosis. Four of the donors were hypertensive, one had diabetes and one smoked. Fourier transform infrared radiography images (FTIRI) were obtained of the calcifications, which had been fixed in 90% ethanol, embedded in polymethyl methacrylate (PMMA) and sectioned. Transmission Electron Microscopy was performed.

Results:  In JDM, electron microscopy documented extensive macrophage and giant cell infiltration; the mineral definitely formed crystals, even within the cytoplasm of the affected cells, whereas in plaque the calcium appeared to be associated with large lipid deposits were not crystalline (verified by EDAX microanalysis).  

Average FTIRI Parameters for the 5 Calcified Aortic Valves
Min/Mat                        CO3/min                        XLR                                 XST
Mean	12	0.0104	4.20	1.10
SD	1.7	0.0013	0.90	0.05
Average FTIRI Parameters for the 5 JDM Deposits
Mean	25	0.014	5.0	1.12
SD	14	0.013	1.8	0.06
Average FTIRI Parameters for 2 Pediatric Iliac Crest Biopsies Cortical Bone
Mean	4.57	0.0065	3.17	1.25
SD	0.64	0.0004	0.02	0.02
Average FTIRI Parameters for 2 Pediatric Iliac Crest Biopsies Cancellous Bone
Mean	4.53	0.0065	3.18	1.20
SD	0.20	0.0003	0.08	0.001

On FTIRI, the mineral/matrix ratio of the calcified aortic valves was greater than in human cortical or cancellous bone, but less than those in JDM deposits; JDM calcifications were much more punctate. The ratios of carbonate to phosphate and the carbonate/matrix ratios were not different from those of bone, nor were the values for collagen maturity and crystallinity. In JDM calcifications, but not calcified aortic valves, intracellular crystals were present.

Conclusion:   The composition and structure of calcifications occurring in aortic valves differ from those that develop in the soft tissue of children with JDM, suggesting that the deposition mechanism differs as well.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-composition-and-structure-of-calcifications-in-juvenile-dermatomyositis-differs-from-calcified-aortic-valves-removed-from-adults-without-jdm/