2026 - MS - All That Glitters: Retro-Orbital Xanthogranuloma or ECD? - Matthew Collin

In this case-based presentation from the Erdheim-Chester Disease Global Alliance (ECDGA) Medical Symposium, Dr. Matthew Collin discusses a complex and atypical histiocytosis case involving orbital inflammation, vascular findings, subtle bone changes, treatment challenges, and evolving molecular testing. Dr. Collin walks through a real-world diagnostic journey that began with inflammatory eye disease and a biopsy initially reported as negative for BRAF mutation using earlier testing methods. The case highlights how patients with suspected histiocytosis may experience delays or uncertainty when findings do not fit classic patterns, and how increased awareness among pathologists, hematologists, radiologists, and specialists can help move the evaluation forward. This presentation covers important topics including: • Diagnostic uncertainty in atypical histiocytosis presentations • Orbital xanthogranuloma and its relationship to Erdheim-Chester Disease • How retro-orbital disease, pituitary stalk changes, vascular findings, and bone findings may influence diagnosis • Subclavian artery stenosis or occlusion as a possible ECD-related feature • The role and limitations of PET/CT, MRI, MRA, and biopsy interpretation • Treatment considerations including steroids, interferon, methotrexate, trametinib, and BRAF/MEK inhibitor therapy • Why tolerability and side effects can strongly shape treatment decisions • The value of sensitive molecular testing such as digital droplet PCR • How repeat or more sensitive testing may identify mutations missed by earlier methods • Why new or growing lesions may require careful evaluation for ECD involvement or a separate diagnosis Dr. Collin also discusses the practical challenges of managing a patient who needed to taper steroids, experienced limited tolerance or response to several therapies, and later had BRAF V600E detected through more sensitive testing. The case underscores how evolving diagnostic tools and multidisciplinary discussion can change management options in rare disease care. This video is part of ECDGA’s mission to raise awareness, provide education and support, and encourage research related to Erdheim-Chester Disease and related histiocytic disorders. The Erdheim-Chester Disease Global Alliance is a 501(c)(3) nonprofit organization dedicated to awareness, support, education, and research for those affected by ECD. Learn more about ECDGA, educational resources, events, research updates, and support opportunities at: https://www.erdheim-chester.org/ Disclaimer: The Erdheim-Chester Disease Global Alliance (ECDGA) does not provide medical advice, diagnoses, or treatments. All content is for informational purposes only. Please consult with a healthcare provider for medical concerns.