Physical examination of a 9-year-old girl with a 2-month history of swelling of the left orbit demonstrated an orbital mass, blepharoptosis, and proptosis. Computed tomography revealed a 2 x 3-cm mass in the superior left orbit that expanded orbital dimensions. Radiography showed abnormalities in the parietal and frontal bones and distal right tibia. Magnetic resonance imaging demonstrated an 8.5-cm abnormality of the marrow space of the right mid-tibia. Bone marrow biopsy was unremarkable. Orbital and tibial biopsies showed a nonspecific chronic inflammation. Idiopathic inflammation that involves the orbit (orbital pseudotumor) and that has systemic manifestations may mimic more serious conditions, such as metastases from rhabdomyosarcoma or Ewing sarcoma, chronic recurrent multifocal osteomyelitis (CRMO), and SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis). Accurate diagnosis requires careful clinical and pathologic examinations.