BACKGROUND: Children with rare bone diseases (RBDs), whether medically complex or not, raise multiple issues in emergency situations. The healthcare burden of children with RBD in emergency structures remains unknown. The objective of this study was to describe the place of the pediatric emergency department (PED) in the healthcare of children with RBD. METHODS: We performed a retrospective single-center cohort study at a French university hospital. We included all children under the age of 18 years with RBD who visited the PED in 2017. By cross-checking data from the hospital clinical data warehouse, we were able to trace the healthcare trajectories of the patients. The main outcome of interest was the incidence (IR) of a second healthcare visit (HCV) within 30 days of the index visit to the PED. The secondary outcomes were the IR of planned and unplanned second HCVs and the proportion of patients classified as having chronic medically complex (CMC) disease at the PED visit. RESULTS: The 141 visits to the PED were followed by 84 s HCVs, giving an IR of 0.60 [95% CI: 0.48-0.74]. These second HCVs were planned in 60 cases (IR = 0.43 [95% CI: 0.33-0.55]) and unplanned in 24 (IR = 0.17 [95% CI: 0.11-0.25]). Patients with CMC diseases accounted for 59 index visits (42%) and 43 s HCVs (51%). Multivariate analysis including CMC status as an independent variable, with adjustment for age, yielded an incidence rate ratio (IRR) of second HCVs of 1.51 [95% CI: 0.98-2.32]. The IRR of planned second HCVs was 1.20 [95% CI: 0.76-1.90] and that of unplanned second HCVs was 2.81 [95% CI: 1.20-6.58]. CONCLUSION: An index PED visit is often associated with further HCVs in patients with RBD. The IRR of unplanned second HCVs was high, highlighting the major burden of HCVs for patients with chronic and severe disease.