Leukemic infiltration of the orbit is relatively uncommon and more characteristic of acute myelogenous leukemia. Orbital involvement may be difficult to distinguish from bacterial or fungal orbital cellulitis. Orbital infiltration can cause proptosis, eyelid swelling, and ecchymosis. It may be best managed by radiation therapy. Granulocytic sarcoma, or chloroma (in reference to the greenish color of involved tissue), is a localized accumulation of myeloid leukemic cells; the tumor may occur anywhere in the body, including in the orbit. This lesion may develop several months before leukemia becomes evident hematologically. Leukemia is discussed in Chapter 28.
In contrast with lymphoma in adults, lymphoma in children very rarely involves the orbit. Burkitt lymphoma, endemic to East Africa and uncommon in North America, is the most likely form to involve the orbit.
Langerhans cell histiocytosis
Langerhans cell histiocytosis (LCH; formerly called histiocytosis X) is the collective term for a group of disorders, usually arising in childhood, that involve abnormal proliferation of histiocytes, often within bone. The disorders are classified as unifocal eosinophilic granuloma of the bone, multifocal eosinophilic granuloma of the bone, and diffuse soft-tissue histiocytosis.
Unifocal eosinophilic granuloma, the most localized and benign form of LCH, produces a bone lesion that involves the orbit, skull, ribs, or long bones in childhood or adolescence. Signs and symptoms may include proptosis, ptosis, and periorbital swelling; localized pain and tenderness are relatively common. CT characteristically shows sharply demarcated osteolytic lesions without surrounding sclerosis (Fig 18-16). Treatment consists of observation of isolated asymptomatic lesions, excision or curettage, systemic or intralesional corticosteroid administration, or low-dose radiation therapy. All modalities have a high rate of success.
Multifocal eosinophilic granuloma of the bone is a disseminated and aggressive form of LCH. It usually presents between 2 and 5 years of age and may produce proptosis from involvement of the bony orbit. Diabetes insipidus is common. Chemotherapy is often required, but the prognosis is generally good.
Diffuse soft-tissue histiocytosis, the most severe form, usually affects infants younger than 2 years. It is characterized by soft-tissue lesions of multiple viscera (liver, spleen) but rarely involves the eye.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.