2020–2021 BCSC Basic and Clinical Science Course™
7 Oculofacial Plastic and Orbital Surgery
Part I: Orbit
Chapter 5: Orbital Neoplasms and Malformations
Langerhans cell histiocytosis (formerly called histiocytosis X) is a collection of rare disorders of the mononuclear phagocytic system (Fig 5-19). These disorders are thought to result from abnormal immune regulation. All subtypes are characterized by an accumulation of proliferating dendritic histiocytes. The disease occurs most commonly in children, with a peak incidence between 5 and 10 years of age, and it varies in severity, from benign lesions with spontaneous resolution to chronic dissemination that results in death. Older names representing the various manifestations of histiocytic disorders (eosinophilic granuloma of bone, Hand-Schüller-Christian disease, and Letterer-Siwe disease) are being replaced by the terms unifocal and multifocal eosinophilic granuloma of bone and diffuse soft tissue histiocytosis.
If sufficiently large, the mass may cause proptosis (see Fig 5-19A, B). Younger children more often present with significant overlying soft-tissue inflammation; they are also more likely to have multifocal or systemic involvement. Even if the initial workup shows no evidence of systemic dissemination, younger patients require regular observation for possible development of multiorgan disease. The most frequent presentation in the orbit is a lytic defect best noted on CT imaging (see Fig 5-19C), usually affecting the superotemporal orbit or sphenoid wing and causing relapsing episodes of orbital inflammation, often initially misdiagnosed as infectious orbital cellulitis. MRI imaging aids in visualization of the soft-tissue component (see Fig 5-19D). Histopathology shows foamy histiocytes with abundant eosinophilic cytoplasm and irregular nuclei that are immunoreactive for antibodies against CD1a (see Fig 5-19E, F).
Figure 5-19 Langerhans cell histiocytosis. A, 18-year-old woman with ptosis of the right upper eyelid, fullness (arrow), and inferior globe displacement. B, Worm’s-eye view demonstrates 2 mm of proptosis of the right eye. C, Coronal CT scan shows lytic erosion of the superotemporal orbital bone (arrows).D, Coronal MRI scan shows the soft tissue with an intracranial and intraorbital component. E, H&E stain of the lesion demonstrates numerous foamy histiocytes. F, Immunohistochemistry with CD1a antibody confirms the diagnosis of Langerhans cell histiocytosis.
(Courtesy of Bobby S. Korn, MD, PhD.)
Histiocytic disorders have a reported survival rate of only 50% in patients who are younger than 2 years at presentation; if the disease develops after age 2, the survival rate rises to 87%. Treatment of localized orbital disease consists of confirmatory biopsy with debulking, which may be followed by intralesional steroid injection or low-dose radiation therapy. Spontaneous remission has also been reported. Although destruction of the orbital bone may be extensive at the time of presentation, the bone usually reossifies completely. Children with systemic disease are treated aggressively with chemotherapy.
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.