AB0902 BONE HEALTH IN PATIENTS WITH JUVENILE ONSET DERMATOMYOSITIS ASSESSED AFTER LONG-TERM FOLLOW-UP; A CASE CONTROL STUDY
Authors: H. Marstein, K. Godang, B. Flatø, I. Sjaastad, J. Bollerslev, H. Sanner
Journal: Annals of the Rheumatic Diseases (2020)

Background: Patients with juvenile dermatomyositis (JDM) are at risk of developing low bone mineral density (BMD) and not reach peak bone mass, mainly due to prednisolone (pred) treatment [1], making them prone to osteoporotic fractures later in life Objectives: To compare BMD in longterm JDM patients (Pts) with that of controls (Ctr); and in Pts explore how disease variables affect BMD. Methods: Pts (n=59) were clinically examined median 16.8y (range 6.6 - 27.0 y) after disease onset and compared 1:1 with age/sex matched Ctr. Dual-energy X-ray absorptiometry (DXA) was used to measure BMD and Z-scores in whole body (WB), lumbar spine at L2-L4 (spine). In those ≥ 20y; also proximal (PR) and distal 1/3 radius (DR), and total hip were examined. Pred at follow up was reported, and cumulative dose calculated. Bone remodeling factors: C-terminal telopeptide (CTX), amino-terminal propeptide (P1NP) and 25(OH)Vitamin D (VitD), were measured in serum. Results: BMD WB was lower in Pts than Ctr, and both WB and spine BMD and Z scores were lower in Pts than Ctr &lt;20 years (Tbl 1). DR BMD and Z-score were both lower in Pts ≥20y. Serum analysis showed lower VitD was lower in Pts than Ctr. In Pts ≥ 20y Vit D was lower and eSR was higher compared to Ctr. In Pts ≥ 20y: moderate negative associations were found between both BMD WB and spine, and pred use at follow up (R`s = -0.43), and between BMD PR and VitD (R= -0.34). There was a positive moderate association between Z-score PR and CTX (-0.45) not found in Ctr, and between Z-score total hip and cumulative pred dose (R = 0.38). All p &lt;0.05. In Pts &lt;20y moderate negative associations were found between Z-score for spine and months of pred use and cumulative pred doses (R`s = -0.40 and -0.48, p&lt;0.05). Other associations found in Pts &lt;20y were also found in respective Ctr. Conclusion: We found that Pts bone health was affected differently in young and adult JDM-Pts. Association analysis between BMD, Z-scores and medication and/or bone remodeling factors were not conclusive. We will perform linear regression analysis to determine if and how BMDs and Z-scores are dependent on pred use, time and doses, and factors important for bone remodeling. Table 1. Characteristics, disease variables, BMD and Z-scores in JDM Pts and Ctr Pts (n=59) Pts &lt; 20y (n=28) Pts ≥ 20y (n=31) Ctr (n=59) Ctr &lt; 20y (n=28) Ctr ≥ 20y (n=31) Age, y 21.5 (6.7-55.4) 15.3 (6.7-19.8) 34.3 (20.4-55.4) 21.6 (6.2-55.4) 14.4 (6.2-20.1) 34.2 (20.5-55.4) Female 36 (61) 20 (71.4) 16 (51.6) 36 (61) 20(71.4) 16 (51.6) BMI, kg/m 2 22.3 (4.8) 20.3 (4.6) 24.0 (4.4) 22.7 (4.5) 21.4 (5.2) 23.9 (3.5) Height, cm 164.9 (14.7) 157.1 (15.9) 171.8 (9.1) 167.3 (15.8)* 159.8 (18.3) 174.0 (9.2) Fracture any 19 (32.2) NA NA 21 (36.8) NA NA BMD, g/cm 2 Whole body 1.10 (0.15) 1.01 (0.13) 1.18 (0.10) 1.13 (0.14)* 1.06 (0.16) † 1.19 (0.08) Spine, L2-L4 1.12 (0.23) 0.99 (0.21) 1.24 (0.18) 1.17 (0.22) 1.07 (0.27)† 1.26 (0.11) Distal radius NA 0.87 (0.09) NA 0.93 (0.11) †† Z-score Whole body -0.07 (1.08) -0.39 (0.99) 0.21 (1.10) 0.27 (0.90) 0.28 (1.01) † † 0.26 (0.71) Spine, L2-L4 -0.16 (1.2.) -0.39 (1.01) 0.06 (1.34) 0.4 (1.02) 0.25 (1.21) † 0.24 (0.84) Distal radius NA -0.76 (1.03) NA -0.05 (0.87)** y: years, BMI: Body mass index, NA: not applicable. Values are: median age (range), median (IQR), n (%) or mean (SD). p-values *p&lt;0.05, **p&lt;0.01 when comparing Pts and Ctr and † p&lt;0.05, †† p&lt;0.01 when comparing Pts and Ctr &lt; and ≥ 20 years. References: [1]Stewart, W.A., et al., Bone mineral density in juvenile dermatomyositis: assessment using dual x-ray absorptiometry. Arthritis Rheum, 2003. 48(8): p. 2294-8. Words: 3555 Disclosure of Interests: None declared