LAUSR

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 lifeTo compare BMD in longterm JDM patients (Pts) with that of controls (Ctr); and in Pts explore how disease variables affect BMD.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.BMD WB was lower in Pts than Ctr, and both WB and spine BMD and Z scores were lower in Pts than Ctr <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 <0.05.In Pts <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<0.05). Other associations found in Pts <20y were also found in respective Ctr.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 CtrPts(n=59)Pts < 20y(n=28)Pts ≥ 20y(n=31)Ctr(n=59)Ctr < 20y(n=28)Ctr ≥ 20y(n=31)Age, y21.5 (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)Female36 (61)20 (71.4)16 (51.6)36 (61)20(71.4)16 (51.6)BMI, kg/m222.3 (4.8)20.3 (4.6)24.0 (4.4)22.7 (4.5)21.4 (5.2)23.9 (3.5)Height, cm164.9 (14.7)157.1 (15.9)171.8 (9.1)167.3 (15.8)*159.8 (18.3)174.0 (9.2)Fracture any19 (32.2)NANA21 (36.8)NANABMD, g/cm2 Whole body1.10 (0.15)1.01 (0.13)1.18 (0.10)1.13 (0.14)*1.06 (0.16) †1.19 (0.08) Spine, L2-L41.12 (0.23)0.99 (0.21)1.24 (0.18)1.17 (0.22)1.07 (0.27)†1.26 (0.11) Distal radiusNA0.87 (0.09)NA0.93 (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 radiusNA-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<0.05, **p<0.01 when comparing Pts and Ctr and † p<0.05, †† p<0.01 when comparing Pts and Ctr < and ≥ 20 years.[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: 3555None declared