Abstract
Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis with protean manifestations, often leading to diagnostic delays. This systematic review synthesizes diagnostic pathways from case reports to optimize clinical recognition. A PRISMA-compliant review of case reports/series (1999–2025) was conducted across six databases. Eligible studies detailed clinical, imaging, histopathologic, or molecular diagnostic steps. Data were extracted on presentation, imaging modalities, biopsy techniques, molecular testing, and delays. Among 1,342 records, 25 studies (24 case reports, 1 series) were included. Common presentations included bone pain (64%), retroperitoneal (28%), and pulmonary involvement (20%). Key imaging findings were bilateral osteosclerosis (72%), "hairy kidneys" (24%), and PET/CT-guided biopsy success (88%). Histopathology confirmed foamy CD68+/CD1a− histiocytes in all cases; BRAFV600E mutations were detected in 80% of tested cases (12/15). Median diagnostic delay was 11 months (IQR: 6–24), often due to misdiagnoses (IgG4-related disease, malignancy). PET/CT and molecular testing reduced delays in recent reports. An integrated approach—combining multisystem imaging (especially PET/CT), targeted biopsy, and BRAF testing—can shorten diagnostic latency. Universal access to molecular diagnostics and multidisciplinary collaboration are critical for timely ECD diagnosis.