P34 Low bone mineral density was associated with lupus nephritis irrespective of duration on steroid treatment in a large observational study of juvenile systemic lupus erythematosus patients.

Background An estimated 10-20% of all patients with systemic lupus erythematosus (SLE) develop clinical disease before the age of 18 years and are therefore classified as juvenile-onset SLE (JSLE). JSLE patients have a higher prevalence of lupus nephritis (LN) compared to adult-onset SLE and decreased long-term survival compared to JSLE patients without LN. We aimed to identify clinical and laboratory predictors of LN in JSLE patients by comparing the baseline characteristics of JSLE patients with and without LN. Methods This is a single-centre retrospective study that included JSLE patients reviewed in our young adult and adolescent clinics after transitioning from paediatric services. All data was analysed descriptively. Mann-Whitney U or Chi-square test were performed to compare the characteristics between patients with and without LN. In addition, we performed uni- and multivariate analysis to investigate potential predictor biomarkers for LN. Results We identified 134 JSLE patients, 45 (34%) of which had LN. 112 (83.6%) of the patients were female and the median age was 22 years (interquartile range [IQR] 20- 24). The median disease duration was longer in the patients with LN (10 years [IQR 8- 14]) in comparison with the patients without LN (8 years [IQR 6- 13]), p = 0.012. As expected, the highest dsDNAlevels ever were observed in patients with LN (p = 0.022). The overall clinical manifestations and complications did not differ between JSLE patients with or without LN, except for the prevalence of low bone mineral density. 16 (35.5%) patients with LN had low bone density and only 11 (12.4%) patients without LN (p = 0.008). Factors associated with low bone mineral density in a univariate logistic regression analysis were: the use of mycophenolate mofetil (p = 0.021) and the presence of LN (p = 0.007), while LN also associated with low bone density (p = 0.008) in a multivariate analysis. Skin involvement was the most common clinical manifestation in both JSLE patient groups. Treatment was more aggressive in patients with LN, including the use of cyclophosphamide, mycophenolate and rituximab, but there was no difference regarding the length of the steroid treatment. The majority of patients (67%) had one flare of nephritis. For the remaining patients, the number of flares ranged from 2 (13%) to 12 (2.2%). The class of nephritis was reported in 34 out of 45 patients, and focal lupus nephritis (class III) was the most common type (44%) reported. There were no statistically significant differences in the baseline characteristics or treatments among the different classes of LN. Conclusion Low bone mineral density in patients with JSLE is well described. However, this is the first study highlighting the association of low bone density with LN independent of total duration of steroid treatment or other clinical manifestations. Conflicts of Interest The authors declare no conflicts of interest. [ABSTRACT FROM AUTHOR]