Vertebral involvement in Erdheim-Chester disease: a case report of non-BRAF-driven diagnosis and treatment challenges.

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis that is frequently misdiagnosed because of its nonspecific systemic symptoms. We report the case of a 73-year-old woman who presented with persistent back pain, abdominal discomfort, and fever. Imaging revealed predominant thoracolumbar vertebral involvement, characterized by multifocal osteosclerosis on computed tomography and abnormal signal intensity with contrast enhancement on magnetic resonance imaging. This radiologic pattern may closely mimic inflammatory disorders, hematologic malignancies, or metastatic disease. Vertebral biopsy established the diagnosis of ECD. Molecular analysis of peripheral blood did not identify actionable driver mutations in the MAPK/PI3K signaling pathways, including BRAF V600E, highlighting the diagnostic and therapeutic challenges associated with non-BRAF-driven ECD. Despite corticosteroid therapy and supportive management, the disease followed an aggressive clinical course with a poor outcome. This case underscores vertebral and bone marrow-dominant ECD as an underrecognized presentation and emphasizes the importance of integrating histopathology, imaging findings, and molecular profiling to reduce diagnostic delay and inform management when targetable mutations are absent.