UC Irvine

Erdheim-Chester disease (ECD) is an exceedingly rare non-Langerhans cell CD68⁺ CD1a^- S100^- histiocytic multi-organ disease. Diagnosis of ECD is often delayed due to non-specific radiographic findings and heterogeneous lesional tissue. Increasingly, the role of genomic alterations is being recognized for both diagnosis and treatment of ECD. More than half of ECD patients harbor the BRAF^V600E mutation. Evaluation for this mutation be can falsely negative on immunohistochemical staining and confirmation with molecular analyses is recommended. We present a case of the 44 year-old male with BRAF^V600E-positive ECD treated successfully with steroids followed by single-agent dabrafenib.