Orbital abscess masquerading as a rhabdomyosarcoma.

Although orbital cellulitis is the most common cause of acute-onset proptosis with inflammatory signs in a child, the clinician should always be alert to the possibility of rhabdomyosarcoma. We describe an unusual presentation of acute-onset nonaxial proptosis of the left orbit without sinus disease or systemic toxicity in a 6-year-old boy. Our clinical differential diagnosis included orbital cellulitis, metastatic disease, capillary haemangioma, lymphangioma with cyst, ruptured dermoid cyst, and orbital rhabdomyosarcoma. Only after orbital biopsy and subsequent microbiologic confirmation were obtained was a diagnosis of chronic orbital abscess tenable. Features in our patient included paucity of symptoms and signs of inflammation. This case illustrates the difficulty in differentiating a chronic orbital infection from orbital rhabdomyosarcoma on the basis of clinical, laboratory, and orbital imaging findings. Possible causes of this unusual presentation are discussed.