POS0391 BONE HEALTH DETERMINANTS IN IDIOPATHIC INFLAMMATORY MYOPATHIES: RESULTS FROM THE ANALYSIS OF A MONOCETRIC COHORT

Background: Idiopathic inflammatory myopathies (IIMs) are rare systemic autoimmune disorders, with a chronic course, frequently associated with osteoporosis (OP), which could complicate with the development of Fragility Fractures (FFx), able to significantly impact on patients' outcomes. It is known that the use of high doses of glucocorticoid (GC) for prolonged periods, an increased osteoclast activity, together with muscle weakness and a reduced mobility could compromise bone health in IIMs. Objectives: The aim of our study was to assess the prevalence and risk factors for FFx in a monocentric cohort of IIMs patients in a third level rheumatology center. Methods: We retrospectively analyzed medical records of consecutive patients diagnosed with IIM according to the EULAR/ACR 2017 criteria, collecting data about demography, clinical characteristics, and quality of life (QoL). QoL was evaluated with Patients Reported Outcomes (PROs): Short-Form 36 Health Survey (SF-36), Functional Assessment of Chronic Illness Therapy Fatigue Subscale (FACIT-F), Health Assessment Questionnaire (HAQ), Hospital Anxiety and Depression Scale (HADS). Intergroups comparisons were assessed by using Chi-square, t-test and ANOVA. P values ≤ 0.05 were considered significant. Results: One hundred ninety-one patients (125 female, 65.4%) with a mean age of 67.3 ± 13.5 years and a mean disease duration of 10.4 ± 7.4 years were enrolled. Eighty-three patients (43.5%) had Dermatomyositis (DM), 78 (40.8%) Polymyositis, 11 (5.7%) Clinically Amyopathic DM, 11 (5.7%) Inclusion Body Myositis, 6 (3.2%) Immune-Mediated Necrotizing Myopathy, 2 (1.1%) Juvenile DM. Seventy patients (36.6%) had OP (64 females, mean age 72.3 years); of these, 29 (15.2% of the total cohort) had FFx (25 females, mean age 72.5 years). Age, female sex and disease duration were risk factors for both OP and FFx (p<0.01). No associations were found between total GC dose and the diagnosis of OP or Ffx. Among comorbidities, the occurrence of a thyroid disorder was significantly associated with a higher risk of developing both OP and FFx (p=0,01); moreover, Hashimoto's thyroiditis (HT) resulted significantly associated with OP development (p=0,003). Furthermore, on multivariate analysis, the presence of a thyroid disease was confirmed as an independent risk factor for OP (p=0,04). The presence of OP was associated with higher HAQ and lower SF-36 values in both physical and emotional domains (p≤0.04). Conclusion: More than one third of the enrolled IIM patients had OP and more than 40% of them had developed at least one FFx. Interestingly, if the total GC dose amount did not seem to significantly impact on these comorbidities, the presence of a thyroid dysfunction, together with age, female gender and disease duration, could significantly impair bone health. Moreover, our data confirmed that OP appears as a main determinant of the disease burden. Therefore, these results stress the need to screen IIM patients for OP and its complications, highlighting the opportunity to assess thyroid function to obtain a more complete and individualized risk profile, aiming at improving both physical and emotional outcomes.