Erdheim-Chester disease with recurrent fever, pneumonia, and autoimmune seropositivity for the BRAF V600E mutation

The 69-year-old male patient presented with recurrent fever, cough, and dyspnea. Upon physical examination, periorbital xanthomatous lesions were identified (Figure 1). CT imaging revealed pulmonary interstitial changes and osteosclerotic bone lesions. Bone scintigraphy revealed multiple, symmetrically distributed bone lesions with relatively increased radiotracer uptake, primarily involving the pectoral and pelvic girdle and the long bones of the limbs. Full body 118F-FDG PET/CT indicated multiple bone density abnormalities with heightened metabolism; pituitary stalk metabolic hyperactivity along with intraspinal metabolically active subdural nodules at the C1 level; multiple nodular metabolic hyperactivities in the bilateral orbits, left parietal region, and left upper lip subcutaneous/cutaneous tissue; bilateral pulmonary interstitial changes/pneumonia with minimal bilateral pleural effusion, pleural thickening, and elevated metabolism. Histopathological analysis from periorbital xanthoma revealed CD68+ foamy histiocytes (S100-, CD1a-), and molecular testing identified a BRAF V600E mutation, ruling out Langerhans cell histiocytosis. The patient’s past medical history included Klebsiella pneumoniae pneumonia, prostate abscess, and autoimmune seropositivity. The diagnosis was confirmed via histopathology and molecular testing. This case underscores the complex and multisystemic presentation of ECD.