Successful Burosumab Treatment in an Adult Patient with X-Linked Hypophosphatemia and Chronic Kidney Disease Stage 3b.

X-linked hypophosphatemic rickets (XLH) is a genetic cause of renal hypophosphatemia due to inactivation of the PHEX gene, with an inappropriate concentration of fibroblast growth factor 23 (FGF23). Burosumab, an anti-FGF23 monoclonal antibody, is a validated treatment for XLH, but its use in patients with chronic kidney disease (CKD) has not been validated. A 61-year-old man with XLH developed CKD during follow-up. Conventional treatment (phosphate salts and active vitamin D analogs) was poorly tolerated. Treatment with burosumab was decided at a multi-professional meeting. Before burosumab initiation, his measured glomerular filtration rate was 44 mL/min/1.73 m2 defining CKD stage 3b and intact FGF23 concentration was very high (4496.0 ng/mL, N: 22.7-93.1) due to both XLH and CKD. Severe hypophosphatemia was observed after the two first injections of burosumab at usual doses (1 mg/kg monthly) and concomitant discontinuation of the conventional treatment. After increasing the dose and reducing the interval between doses (1.3 mg/kg every three weeks) from the third injection, serum phosphate concentration normalized and remained around the lower limit of the normal range. A local cutaneous reaction was observed just after the second injection, but did not recur. We report for the first time the efficacy and good short-term tolerance of burosumab in a patient with XLH and CKD, subject to a higher dosage aimed at achieving a phosphatemia at the lower limit of the normal range.

Fully automated opportunistic screening of vertebral fractures and osteoporosis on more than 150 000 routine computed tomography scans.

OBJECTIVE: Osteoporosis is underdiagnosed and undertreated, although severe complications of osteoporotic fractures, including vertebral fractures, are well known. This study sought to assess the feasibility and results of an opportunistic screening of vertebral fractures and osteoporosis in a large database of lumbar or abdominal CT scans. MATERIAL AND METHODS: Data were analysed from CT scans obtained in 35 hospitals from patients aged 60 years or older and stored in a Picture Archiving and Communication System in Assistance-Publique-Hôpitaux de Paris, from 2007 to 2013. Dedicated software was used to analyse the presence or absence of at least 1 vertebral fracture (VF), and the radiodensity of the lumbar vertebrae was measured Hounsfield Units (HUs). A simulated T-score was calculated. RESULTS: Data were analysed from 152 268 patients [mean age (S.D.) = 73.2 (9.07) years]. Success rates for VF assessment and HUs measurements were 82 and 87%, respectively. The prevalence of VFs was 24.5% and increased with age. Areas under the receiver operating characteristic curves for the detection of VFs were 0.61 and 0.62 for the mean HUs of the lumbar vertebrae and the L1 HUs, respectively. In patients without VFs, HUs decreased with age, similarly in males and females. The prevalence of osteoporosis (sT-score ≤ -2.5) was 23.8% and 36.5% in patients without and with VFs, respectively. CONCLUSION: It is feasible on a large scale to screen for VFs and osteoporosis during opportunistic screening in patients 60 years or older having lumbar or abdominal CT.

Efficacy of Burosumab in Adults with X-linked Hypophosphatemia (XLH): A Post Hoc Subgroup Analysis of a Randomized Double-Blind Placebo-Controlled Phase 3 Study.

The anti-fibroblast growth factor 23 monoclonal antibody burosumab corrects hypophosphatemia in adults with X-linked hypophosphatemia (XLH) and improves pain, stiffness, physical function, and fatigue. This post hoc subgroup analysis used data from the 24-week placebo-controlled period of a phase 3 study in 134 adults with XLH (ClinicalTrials.gov NCT02526160), to assess whether the benefits of burosumab are evident in 14 clinically relevant subgroups defined by baseline demographic and functional criteria, including sex, Brief Pain Inventory-short form (BPI-SF) Average And Worst Pain, region, race, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC®) Stiffness, Physical Function and Pain domains and total score, use of opioid/other pain medication, active fractures/pseudo-fractures, and 6-min walk test distance. There were no statistically significant interactions between any of the subgroups and treatment arm for any endpoint. Higher proportions of subjects achieved mean serum phosphate concentration above the lower limit of normal (the primary endpoint) with burosumab than with placebo in all subgroups. For the key secondary endpoints (WOMAC Stiffness and Physical Function; BPI-SF Worst Pain) individual subgroup categories showed improvements with burosumab relative to placebo. For additional efficacy endpoints, burosumab was favored in some subgroups but differences were not significant and confidence intervals were wide. For some endpoints the treatment effect is small at 24 weeks in all subjects. This subgroup analysis shows that burosumab was largely superior to placebo across endpoints in the 14 clinically relevant subgroup variables at 24 weeks and is likely to benefit all symptomatic adults with active XLH.

Barriers and Expectations for Patients in Post-Osteoporotic Fracture Care in France: The EFFEL Study.

OBJECTIVES: This study aimed to quantify the relative importance of barriers to better secondary prevention of osteoporotic fractures and of care expectations expressed by patients with osteoporotic fractures in France. METHODS: A qualitative exploration of potential barriers to care and expectations was undertaken through a systematic literature review and in-depth patients interviews. A list of 21 barriers and 21 expectations was identified. These were presented to 324 subjects with osteoporotic fractures, identified in a representative sample of the French population, in the form of best-worst scaling questionnaires. Patients rated the relative importance of the attributes, and arithmetic mean importance scores were calculated and ranked. A Bayesian hierarchical model was also performed to generate a relative importance score. Latent class analysis was performed to identify potential subgroups of patients with different response profiles. RESULTS: A total of 7 barriers were rated as the most important, relating to awareness of osteoporosis and coordination of care. The highest-ranked barrier, "my fracture is not related to osteoporosis," was significantly more important than all the others (mean importance score 0.45; 95% confidence interval 0.33-0.56). A similar ranking of attributes was obtained with both the arithmetic and the Bayesian approach. For expectations, no clear hierarchy of attributes was identified. Latent class analysis discriminated 3 classes of respondents with significant differences in response profiles (the educated environmentalists, the unaware, and the victims of the system). CONCLUSIONS: Better quality of care of osteoporosis and effective secondary fracture prevention will require improvements in patient education, training of healthcare professionals, and coordination of care.

2019 EULAR points to consider for non-physician health professionals to prevent and manage fragility fractures in adults 50 years or older.

OBJECTIVE: To establish European League Against Rheumatism (EULAR) points to consider for non-physician health professionals to prevent and manage fragility fractures in adults 50 years or older. METHODS: Points to consider were developed in accordance with EULAR standard operating procedures for EULAR-endorsed recommendations, led by an international multidisciplinary task force, including patient research partners and different health professionals from 10 European countries. Level of evidence and strength of recommendation were determined for each point to consider, and the mean level of agreement among the task force members was calculated. RESULTS: Two overarching principles and seven points to consider were formulated based on scientific evidence and the expert opinion of the task force. The two overarching principles focus on shared decisions between patients and non-physician health professionals and involvement of different non-physician health professionals in prevention and management of fragility fractures. Four points to consider relate to prevention: identification of patients at risk of fracture, fall risk evaluation, multicomponent interventions to prevent primary fracture and discouragement of smoking and overuse of alcohol. The remaining three focus on management of fragility fractures: exercise and nutritional interventions, the organisation and coordination of multidisciplinary services for post-fracture models of care and adherence to anti-osteoporosis medicines. The mean level of agreement among the task force for the overarching principles and the points to consider ranged between 8.4 and 9.6. CONCLUSION: These first EULAR points to consider for non-physician health professionals to prevent and manage fragility fractures in adults 50 years or older serve to guide healthcare practice and education.

Changes in bone formation regulator biomarkers in early axial spondyloarthritis.

OBJECTIVE: The hallmark of advanced axial SpA (axSpA) is spine ankylosis due to excessive ectopic bone formation. This prospective study aimed to describe the changes in serum levels of different regulators [sclerostin, dickkopf-1 (DKK-1)] and markers of bone formation [bone morphogenetic protein 7 (BMP-7)] over 5 years in early axSpA patients and to assess determinants of such changes. METHODS: The DEvenir des Spondyloarthropathies Indifférenciées Récentes cohort is a prospective, multicentre French study of 708 patients with early (>3 months-<3 years) inflammatory back pain suggestive of axSpA. Serum levels of BMP-7, sclerostin and DKK-1 were assessed at baseline and after 2 and 5 years. Changes in bone formation regulators over time were analysed using mixed linear models. RESULTS: Serum BMP-7 significantly increased over time, with a median relative change of 223.7% [interquartile range (IQR) 0-10 700 (0.17 pg/ml/month), P < 0.001]. Serum sclerostin significantly increased over time, with a median relative change of 14.8% [IQR -7.9-41.4% (0.001 ng/ml/month), P < 0.001]. Serum DKK-1 did not significantly change over time. Serum BMP-7 increased over time in active disease (Ankylosing Spondylitis Disease Activity Score with CRP ≥1.3, P = 0.01), but the increase was less pronounced with TNF inhibitor (TNFi) use (P < 0.001). No determinant was associated with serum sclerostin change. CONCLUSION: Serum BMP-7 change over 5 years was related with inflammation; it was increased in active disease, but the increase was low with TNFi use. Serum sclerostin levels significantly increased over time, but to a lesser degree than for serum BMP-7. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/, NCT01648907.

Bone mineral density at extremely low weight in patients with anorexia nervosa.

OBJECTIVE: Low bone mineral density (BMD) is a frequent and invalidating consequence of chronic undernourishment in patients with anorexia nervosa (AN). The aim of this study was to assess prevalence and clinic-biological correlates of low BMD and fractures in extremely undernourished inpatients with AN. DESIGN: Retrospective cohort study. PATIENTS AND MEASUREMENTS: This study included 97 extremely malnourished female inpatients with AN consecutively admitted over 2 years. Clinical-biological variables, history of fractures and BMD by dual-energy X-ray absorptiometry (DXA) were examined to find predictors of low BMD and fractures. RESULTS: The prevalence of low BMD was of 51% for lumbar spine and 38% for femoral neck. Z-scores were lower at lumbar spine (-2.2 ± 1.2 SD) than at femoral neck (-1.9 ± 0.9 SD) (P<.01). Fragility fractures were reported by 10% of patients. BMD was mainly predicted by FFM, illness duration, age at onset and restricting AN (P<.05). Fractures were predicted by sodium concentrations, femoral neck Z-score and illness duration (P<.03). CONCLUSION: Extremely severe patients with AN have high prevalence of low BMD, predicted by severity and chronicity of malnutrition.

The Causes of Hypo- and Hyperphosphatemia in Humans.

Phosphate homeostasis involves several major organs that are the skeleton, the intestine, the kidney, and parathyroid glands. Major regulators of phosphate homeostasis are parathormone, fibroblast growth factor 23, 1,25-dihydroxyvitamin D, which respond to variations of serum phosphate levels and act to increase or decrease intestinal absorption and renal tubular reabsorption, through the modulation of expression of transcellular transporters at the intestinal and/or renal tubular level. Any acquired or genetic dysfunction in these major organs or regulators may induce hypo- or hyperphosphatemia. The causes of hypo- and hyperphosphatemia are numerous. This review develops the main causes of acquired and genetic hypo- and hyperphosphatemia.

Handgrip strength is a comorbidity marker in systemic necrotizing vasculitides and predicts the risk of fracture and serious adverse events.

OBJECTIVE: Sarcopenia has been associated with poor outcomes in various medical and surgical conditions. However, its impact in systemic necrotizing vasculitides (SNV) had never been characterized. We aimed to assess the prevalence, associated factors and prognostic impact of sarcopenia in SNV. METHODS: Patients with SNV were successively included in a prospective longitudinal study assessing comorbidities. At inclusion, we evaluated sarcopenia by assessing skeletal muscle mass index using DXA and muscle strength using handgrip strength. Vasculitis and treatments-related events were recorded and analysed using Cox models. RESULTS: One hundred and twenty patients were included. At inclusion, low handgrip strength (<30 kg for men and 20 kg for women) was identified in 28 (23%) patients, while no patient exhibited low skeletal muscle mass index (<7.23 kg/m2 for men and 5.67 kg/m2 for women). Low handgrip strength was associated with age (P <0.0001), type of vasculitis (P =0.01), vasculitis damage index (P =0.01), history of falls (P =0.0002), osteoporosis (P =0.04), low serum albumin (P =0.003) and prealbumin (P =0.0007), high CRP (P =0.001), high FRAX® tool (P =0.002) and low bone mineral density at femoral neck (P =0.0002). After median follow-up of 42 months, low handgrip strength was associated with higher risk of bone fracture [HR 4.25 (1.37-13.2), P =0.01] and serious adverse events [HR 2.80 (1.35-5.81), P =0.006]. CONCLUSION: Handgrip strength is associated in SNV with nutritional status and comorbidities such as bone disease, and seems to predict, as in other medical conditions, the risk of fracture and serious adverse events during follow-up. In contrast, assessment of skeletal muscle mass index in this population remains uncertain.

Low incidence of vertebral fractures in early spondyloarthritis: 5-year prospective data of the DESIR cohort.

OBJECTIVES: An increased risk of vertebral fractures (VFs) has been reported in spondyloarthritis (SpA). Our hypothesis is that the prevalence of VFs is lower than reported in previous studies, especially in early SpA. This study aimed at assessing the incidence of radiographical VFs over 5 years in early axial SpA. METHODS: The DESIR (DEvenir des Spondylarthropathies Indifférenciées Récentes) cohort, which included patients with inflammatory back pain highly suggestive of axial SpA, is the basis of this study. All radiographs of the DESIR cohort had been assessed at a central facility, by one investigator specialised in the field of the diagnosis of VFs according to Genant's method. We assessed the prevalence and incidence of VFs and vertebral deformities at baseline and over 5 years. RESULTS: Five-year X-rays were available for 432 patients (mean age 34.3±8.7 years, 53% women). Diagnosis of VF was doubtful and needed adjudication for 19 patients (4.4%). 13 patients had prevalent VFs (3.0%) which were located at the thoracic spine (12 were grade 1). At 5 years, five patients had an incident VF (1.15%); seven vertebrae were fractured, mostly located at the thoracic spine (n=6/7), and of grade 1 (n=6/7). CONCLUSION: In the DESIR cohort, a population of early SpA, we found a low prevalence and incidence of VFs (3.0% and 1.15 %), respectively. This confirms our hypothesis that the actual prevalence and incidence of VFvertebral fracture in SpA is lower than that reported in the previous studies.

Continued Beneficial Effects of Burosumab in Adults with X-Linked Hypophosphatemia: Results from a 24-Week Treatment Continuation Period After a 24-Week Double-Blind Placebo-Controlled Period.

Burosumab, a fully human monoclonal antibody to FGF23, is the only approved treatment for X-linked hypophosphatemia (XLH), a rare genetic disorder characterized by renal phosphate wasting and substantial cumulative musculoskeletal morbidity. During an initial 24-week randomized, controlled trial, 134 adults with XLH received burosumab 1 mg/kg (n = 68) or placebo (n = 66) every 4 weeks. After 24 weeks, all subjects received open-label burosumab until week 48. This report describes the efficacy and safety of burosumab during the open-label treatment period. From weeks 24-48, serum phosphorus concentrations remained normal in 83.8% of participants who received burosumab throughout and were normalized in 89.4% who received burosumab after placebo. By week 48, 63.1% of baseline fractures/pseudofractures healed fully with burosumab, compared with 35.2% with burosumab after placebo. In both groups, burosumab was associated with clinically significant and sustained improvement from baseline to week 48 in scores for patient-reported outcomes of stiffness, pain, physical function, and total distance walked in 6 min. Rates of adverse events were similar for burosumab and placebo. There were no fatal adverse events or treatment-related serious adverse events. Nephrocalcinosis scores did not change from baseline by more than one grade at either week 24 or 48. These data demonstrate that in participants with XLH, continued treatment with burosumab is well tolerated and leads to sustained correction of serum phosphorus levels, continued healing of fractures and pseudofractures, and sustained improvement in key musculoskeletal impairments.

Abdominal adipose tissue predicts major cardiovascular events in systemic necrotising vasculitides.

OBJECTIVES: Cardiovascular (CV) events are highly prevalent in systemic necrotising vasculitides (SNV). Visceral/subcutaneous adipose tissue (VAT/SAT) ratio has been shown to be associated with CV events in various diseases. We aimed to assess the relevance of abdominal adipose tissue measurement to predict major CV events (MCVEs) in SNV. METHODS: Patients with SNV were successively included in a longitudinal study assessing MCVEs and other sequelae. Dual x-ray absorptiometry was performed to evaluate abdominal adipose tissue. Patients were prospectively followed for MCVEs, defined as myocardial infarction, unstable angina, stroke, arterial revascularisation and/or hospitalisation for or death from CV causes. RESULTS: One hundred and twenty consecutive SNV patients were included and analysed (54 males, mean age 53±18 years). High CV risk was found in 28 (23.3%) patients. In univariate analysis, age, male gender, VDI, VAT/SAT ratio and serum troponin level were significantly associated with high CV risk, whereas age and VAT/SAT ratio remained independently associated with high CV risk. Variables associated with high tertile of VAT/SAT ratio included age and metabolic risk factors. After median follow-up of 42 months, 19 (16%) patients experienced MCVEs. Hazard ratios for incident MCVEs compared with 1st tertile of VAT/SAT ratio were 7.22 (1.02-51.3; p=0.048) and 9.90 (3.15-31.2; p=0.0002) in the 2nd and 3rd tertile, respectively. CONCLUSIONS: Abdominal visceral adipose tissue is a reliable surrogate marker of CV risk and predicts incident MCVEs in SNV patients. Abdominal adipose tissue should be probably evaluated routinely in these patients to assess CV risk.

Fracture Liaison Services.

PURPOSE OF REVIEW: The purpose of this review is to report the evidence of beneficial effects of Fracture Liaison Service (FLS) including data regarding their impact on subsequent fracture, mortality risk and cost-effectiveness. This review also discusses the limitations of these data and the challenges faced during the implementation of FLS. RECENT FINDINGS: Recent studies showed the beneficial impact of implementation of FLS on the prevention of subsequent fracture risk, reduced mortality and cost-effectiveness. However, heterogeneity of FLS models and small number of studies limited the conclusion about the impact of FLS on secondary fracture prevention. SUMMARY: Patients with osteoporosis-related fractures are at higher risk of subsequent refractures. These subsequent fractures are associated with increased morbidity and premature mortality. However, there is a gap between evidence-based recommendations for postfracture care and actual clinical practice. FLS care is recommended for the management of the prevention of secondary fracture. FLS implementation reduces the risk of subsequent fracture, but the level of evidence is low as the interpretation of data is limited by the number of studies and their heterogeneity. FLS care significantly reduces the postfracture mortality, especially in patients with hip fractures. FLS implementation is cost-effective compared with usual care. Additional studies (with large sample and long-term follow-up) are needed to assess the impact of FLS care on subsequent fracture risk.

Bone loss in patients with early inflammatory back pain suggestive of spondyloarthritis: results from the prospective DESIR cohort.

OBJECTIVES: The objectives of the study were to assess the 2 year BMD changes and their determinants in patients with early inflammatory back pain suggestive of axial spondyloarthritis (SpA) (DESIR cohort). METHODS: A total of 265 patients (54% male, mean age 34.4 years) had BMD measurements at baseline and at 2 years. Low BMD was defined as a Z score ≤-2 (at at least one site) and significant bone loss was defined by a decrease in BMD ≥0.03 g/cm(2). Clinical, biological and imaging parameters were assessed over 2 years. RESULTS: Thirty-nine patients (14.7%) had low BMD at baseline; 112 patients (42.3%) had a 2 year significant bone loss. One hundred and eighty-seven (70.6%) used NSAIDs at baseline and 89 (33.6%) received anti-TNF therapy over 2 years. In anti-TNF users, BMD significantly increased at the lumbar spine and did not change at the hip site from baseline. In multivariate analysis, baseline use of NSAIDs [odds ratio (OR) 0.38, P = 0.006] had a protective effect on hip bone loss. In patients without anti-TNF treatments, baseline use of NSAIDs (OR 0.09, P = 0.006) and a 2 year increase in BMI (OR 0.55, P = 0.003) had protective effects on hip bone loss, whereas a 2 year increase in fat mass was associated with hip bone loss (OR 1.18, P = 0.046). CONCLUSION: Among patients with symptoms suggestive of early axial SpA, 42.3% of patients have significant bone loss over 2 years. Anti-TNF therapy is protective against bone loss and baseline use of NSAIDs has a protective effect on hip bone loss.

High rate of progression to symptomatic multiple myeloma in patients with smoldering myeloma and isolated osteoporotic vertebral fracture.

Multiple myeloma (MM) frequently causes vertebral fractures (VF). Some are lytic lesions and others have the aspect of benign osteoporotic fractures not requiring anti-myeloma treatment. We explored outcome of these patients with smoldering myeloma (SM) and osteoporotic VF. In this retrospective bi-centric study, patients were identified using a systematic keyword search on electronic medical records. Patients with SM and isolated VF of osteoporotic aspect without indications for myeloma-specific therapy were included. Overall, 13 (7 %) of the 184 identified patients had SM and VF confirmed to be osteoporotic (median number of VF was 3). During follow-up, 12 (92 %) patients evolved to symptomatic MM, 7 (54 %) of them within 18 months (early progressors). Myeloma defining events were new lytic bone lesions in 7 patients (53.8 %). The serum calcium level was significantly higher in the early progressor group (median 2.35 IQR [2.31-2.38] and 2.28 IQR [2.21-2.29] respectively, p = 0.003). Early progressors had a higher number of VF at diagnosis (3.0 [2.0-5.5] vs 1.0 [1.0-2.5], p = 0.18) and more frequently evolved to symptomatic MM because of lytic bone lesions (5 [71 %] vs 2 [33 %], p = 0.13) compared to late progressors. VF of osteoporotic appearance in the context of SM is a rare situation but at high risk of rapid progression to symptomatic MM, suggesting that they may represent bone fragility linked to MM infiltration rather than solely osteoporotic fractures. Further studies are needed to assess if earlier treatment might be beneficial in this population.

Improved Oral Health in Adults with X-Linked Hypophosphatemia Treated with Burosumab.

CONTEXT: X-linked hypophosphatemia (XLH) is a rare genetic bone disease affecting both children and adults, with oral manifestations such as spontaneous dental infections. The main treatments for XLH are conventional treatment (CT) with oral phosphate salts and active vitamin D supplementation, and burosumab, an antibody targeting Fibroblast Growth Factor 23 (FGF23). While the beneficial effect of CT on oral manifestations is established, the effect of burosumab on oral health is unknown, especially in adults. OBJECTIVE: We aimed to compare the oral health (number of missing or endodontically treated teeth and presence of periodontal disease) and incidence of endodontic infections of adult patients with XLH according to their treatment's modalities (no treatment, CT, or burosumab). METHODS: This was achieved through a single-center, retrospective analysis of oral health data from 44 patients who had undergone dental monitoring for at least 6 months. RESULTS: Oral health varied according to the proportion of their adult life spent under treatment for XLH and the incidence of dental infections during follow-up was influenced by the type of treatment received. There was a 55.9% reduction of infections during CT and an 86.4% reduction during burosumab treatment compared to periods with no treatment (P < 0.0001). Comparing treatment and non-treatment periods within the same patient showed a strong association between burosumab treatment and decreased infection incidence (0.006 vs 0.09 infection per month, P<0.01). CONCLUSIONS: We observed that adults with XLH treated with burosumab developed fewer endodontic infections during dental follow-up than patients who were untreated or received CT.

Real-world non-interventional post-authorization safety study of long-term use of burosumab in children and adolescents with X-linked hypophosphatemia: first interim analysis.

Background: X-linked hypophosphatemia (XLH) is a rare, progressive disorder characterized by excess fibroblast growth factor 23 (FGF23), causing renal phosphate-wasting and impaired active vitamin D synthesis. Burosumab is a recombinant human monoclonal antibody that inhibits FGF23, restoring patient serum phosphate levels. Safety data on long-term burosumab treatment are currently limited. Objectives: This post-authorization safety study (PASS) aims to monitor long-term safety outcomes in children and adolescents (1-17 years) treated with burosumab for XLH. This first interim analysis reports the initial PASS safety outcomes. Design: A 10-year retrospective and prospective cohort study. Methods: This PASS utilizes International XLH Registry (NCT03193476) data, which includes standard diagnostic and monitoring practice data at participating European centers. Results: At data cut-off (13 May 2021), 647 participants were included in the International XLH Registry; 367 were receiving burosumab, of which 67 provided consent to be included in the PASS. Mean (SD) follow-up time was 2.2 (1.0) years. Mean (SD) age was 7.3 (4.3) years (range 1.0-17.5 years). Mean duration of burosumab exposure was 29.7 (25.0) months. Overall, 25/67 participants (37.3%) experienced ⩾1 adverse event (AE) during follow-up; 83 AEs were reported. There were no deaths, no AEs leading to treatment withdrawal, nor serious AEs related to treatment. The most frequently reported AEs were classified as 'musculoskeletal and connective tissue disorders', with 'pain in extremity' most frequently reported, followed by 'infections and infestations', with 'tooth abscess' the most frequently reported. Conclusion: In this first interim analysis of the PASS, covering the initial 2 years of data collection, the safety profile of burosumab is consistent with previously reported safety data. The PASS will provide long-term safety data over its 10-year duration for healthcare providers and participants with XLH that contribute to improvements in the knowledge of burosumab safety. Trial registration: European Union electronic Register of Post-Authorisation Studies: EUPAS32190.

Bone oedema on MRI is highly associated with low bone mineral density in patients with early inflammatory back pain: results from the DESIR cohort.

OBJECTIVES: To assess bone mineral density (BMD) at lumbar spine and hip in a large cohort of patients with early inflammatory back pain (IBP) suggestive of axial spondyloarthritis (SpA), and to assess systemic and bone inflammation (according to MRI) as risk factors of low BMD. PATIENTS AND METHODS: 332 (52.4% male) patients with IBP suggestive of axial SpA defined by Calin or Berlin criteria were recruited; they had lumbar spine and hip BMD and body composition measurements. Low BMD was defined by Z≤-2 (at least one site). Clinical, biological (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)) and imaging (x-rays, spine and sacroiliac joint MRI) parameters were compared in patients with and without low BMD (Z≤-2). Significant parameters in univariate analysis were tested in multivariate models. RESULTS: Patients (mean age 33.8 years) had a short duration of axial symptoms (mean 1.6 years); 71.4% fulfilled the Assessment of Spondyloarthritis International Society criteria for axial SpA and HLA-B27 was present in 62.1%. 43 (13.0%) had low BMD (88% male). Multivariate logistic regression showed that parameters significantly associated with low BMD (any site) were the presence of bone marrow oedema (inflammatory lesions) on MRI (OR 4.63, p=0.001), either ESR or CRP (OR 2.60, p=0.037) and male gender (OR 9.60, p=0.0004). CONCLUSIONS: This study conducted in a large cohort of young adults with early IBP suggestive of SpA shows that 13.0% of patients have a low BMD and that the main risk factor associated with low BMD was inflammation on MRI.