Background/Purpose: Prior studies have estimated that 20% of adult dermatomyositis (DM) patients suffer from calcinosis.  Although calcinosis is related to persistent disease activity, poor treatment adherence, and therapy refractoriness in juvenile DM (JDM) patients, risk factors for calcinosis in the adult DM population have not been extensively studied.  Antibodies to nuclear matrix protein 2 (NXP-2) have been associated with calcinosis in JDM patients but only one study has shown a trend for this association in adult DM.  We aimed to determine the prevalence of calcinosis and to identify associated clinical features in a large cohort of adult DM patients. 

Methods: This is a cross-sectional study of 126 patients diagnosed with DM at Stanford University Medical Center between 01/2006 and 01/2013. Calcinosis was defined as the presence of calcium deposition in the skin and/or subcutaneous tissues as determined by physical examination and/or radiography. Logistic regression was used to obtain odds ratios (OR) relating calcinosis to various clinical features using both univariate and multivariate analyses. 

Results: 94% of patients had DM-specific or myositis-specific autoantibodies (against NXP-2, transcription intermediary factor-gamma (TIF-g), melanoma differentiation antigen 5 (MDA-5), sumoyl activating enzyme (SAE1/2), Mi-2, or Jo-1). A total of 14 (11%) patients had calcinosis. In univariate analysis, longer disease duration (OR=1.1, 95%CI 1.01–1.3, p=0.03), digital ulcers (OR=9.8, 95%CI 2.9–33.6, p=0.0003), interstitial lung disease (OR=6.5, 95%CI 1.9–22.2, p=0.003), autoantibodies to MDA-5 (OR=5.1, 95%CI 1.4–17.8, p=0.01) and antibodies to Ro52 (OR=3.5, 95%CI 1.1-11.0, p=0.04) were positively associated with calcinosis while autoantibodies to TIF-g were negatively associated with calcinosis (OR=0.19, 95%CI 0.04–0.91, p=0.04). The association between anti-NXP-2 and calcinosis reached statistical significance only in multivariate analysis (OR=7.6, 95%CI 1.5–39.2, p=0.01), while MDA-5 and TIF-g were no longer significantly associated in these models. Because of the known association between MDA-5 and digital ulcers, we evaluated a multivariate model excluding digital ulcers, and found that MDA-5 positivity was highly predictive of calcinosis (OR=6.9, 95%CI 1.8–27, p=0.005).  Digital ulcers were strongly associated with calcinosis in all multivariate models, independent of the underlying autoantibody present (Table 1). 

Conclusion: Calcinosis was a relatively uncommon clinical feature in our cohort of DM patients. We found an association between calcinosis and anti-NXP-2 autoantibodies as well as a novel association with digital ulcers. A common vascular mechanism may underlie the development of both calcinosis and digital ulcers in patients with DM.

Table 1. Predictors of calcinosis in multivariate analyses.

	OR	95%CI	p-value
Multivariate model 1
Disease duration	1.2	1.04 – 1.38	0.01
Digital ulcers	23.1	4.74 – 112	<0.001
NXP-2	7.6	1.48 – 39.2	0.01
Multivariate model 2
Disease duration	1.17	1.04 – 1.33	0.01
Digital ulcers	12.8	2.12 – 77.2	0.005
MDA-5	1.19	0.17 – 8.04	0.85
Multivariate model 3
Disease duration	1.16	1.03 – 1.3	0.01
MDA-5	6.9	1.76 – 27	0.005
Multivariate model 4
Disease duration	1.16	1.03 – 1.33	0.01
Digital ulcers	13.9	3.31 – 58.6	0.0003
TIF-g	0.24	0.04 – 1.25	0.09

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/identification-of-clinical-features-and-risk-factors-associated-with-calcinosis-in-adult-patients-with-dermatomyositis/