9-year-old female presenting with l lower leg pain diagnosed with erdheim-chester disease (ECD)

Abstract Background: Erdheim-Chester disease (ECD) is a non-Langerhans histiocytic disorder that commonly includes osteosclerotic lesions of the bones and sheets of foamy histiocytes on biopsy with a distinct immunophenotype.It is most common in adult males, with few pediatric cases reported (Goyal et al., 2020). While bony manifestations are the most common, the clinical manifestations of ECD are variable and can involve many different organ systems (Emile et al., 2020). Method:This study was done by retrospective review of electronic medical records. Results: Our patient is a 9-year-old female who presented with left lower leg pain, found to have a radiolucent lesion on imaging. Pathology from open bone biopsy of her left tibia was consistent with non-Langerhans histiocytosis. Further imaging exhibited diffuse lytic lesions throughout the skeleton, without evidence of visceral organ involvement. Cytokine panel was remarkable for elevation in IL6, and patient received bridging therapy with tocilizumab infusion. Patient was then started on targeted biologic therapy, dabrafenib with rapid improvement in symptoms. Disease assessment with PET CT after 3 months of treatment showed complete metabolic response of her bony lesions. She has continued dabrafenib monotherapy with excellent tolerance and exhibiting minimal side effects. Conclusion: As no standard treatment guideline exist for pediatric patients with ECD, case reports have focused on use of and outcomes of therapies such as steroids, chemotherapy, interferon alfa and targeted biologics in attempt to better optimize treatment (Pegoraro et al., 2023). The aim of this report is to further highlight how ECD can present in pediatric populations and present treatment response to dabrafenib and targeted cytokine inhibition in a pediatric patient with BRAFV600E mutation and diffuse bony involvement. ReferencesGoyal G, Heaney ML, Collin M, et al. Erdheim-Chester disease: consensus recommendations for evaluation, diagnosis, and treatment in the molecular era. Blood. 2020;135(22):1929-1945.Emile JF, Abla O, Fraitag S, et al. Goyal G, Heaney ML, Collin M, et al. Erdheim-Chester disease: consensus recommendations for evaluation, diagnosis, and treatment in the molecular era. Blood. 2020;135(22):1929-1945.Pegoraro F, Mazzariol M, Trambusti I, et al. Childhood-onset Erdheim-Chester disease in the molecular era: clinical phenotypes and long-term outcomes of 21 patients. Blood 2023;142(13):1167-1171