Idiopathic Orbital Inflammation
Idiopathic orbital inflammation (IOI), formerly called orbital pseudotumor, is an unusual orbital-specific disorder of unknown origin, characterized by nonspecific orbital inflammation. It can affect any or all of the orbital structures but, most frequent
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Idiopathic Orbital Inflammation Ilse Mombaerts
Introduction Idiopathic orbital inflammation (IOI) is a term applied to a poorly understood orbit-specific disorder characterized by an enlarged orbital structure or mass consisting of nonspecific inflammation without identifiable local or systemic cause [1]. Based on the primary involvement of anatomic structures, IOI is anatomically categorized into idiopathic dacryoadenitis (lacrimal gland) and idiopathic orbital myositis (extraocular muscles). When located in the orbital fibrofatty matrix or involving several structures, it is grossly referred to as – diffuse – IOI. Myositis represents a specific subentity and is segregated as myositic IOI, with the other lesions (i.e., idiopathic dacryoadenitis, orbital fat IOI) as nonmyositic IOI. Depending on histologic findings, nonmyositic IOI is further subdivided into sclerosing and nonslerosing IOI (Table 7.1) [2].
I. Mombaerts (*) Department of Ophthalmology, University Hospitals Leuven, Leuven, Belgium Department of Neurosciences, Catholic University Leuven, Leuven, Belgium e-mail: [email protected] © Springer Nature Switzerland AG 2019 C. J. Hwang et al. (eds.), Clinical Ophthalmic Oncology, https://doi.org/10.1007/978-3-030-13558-4_7
Table 7.1 Idiopathic orbital inflammation: clinical and histopathological categories Clinical Predominant category involvement Orbital myositis Extraocular muscles Dacryoadenitis Lacrimal gland Diffuse orbital inflammation
Fibrofatty matrix or involving several structures
Histopathological categories
Sclerosing Nonsclerosing Sclerosing Nonsclerosing
Historical Perspective and Terminology In Victorian and Edwardian times, space- occupying lesions were commonly considered malignant until proven otherwise, relying on surgical exploration, histological examination and observation. The earliest reported possible case of IOI can be traced back to 1850, describing the illustrious patient Austrian Field Marshal Count Radetzky sufferring from a clinically suspected malignant orbital tumor who was cured with homeopathic treatment [3]. In 1895, Panas coined the French term pseudoplasm malin to describe lesions presenting as a malignant tumor but appearing to be benign on follow-up. The recognition of idiopathic orbital myositis dates back to 1903, when Gleason described a patient with the clinical symptoms of a rapid onset, aggressive 61
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bilateral orbital tumor which displayed on histopathological examination inflamed extraocular muscles. In 1905, Birch-Hirschfeld, the son to a pathologist, introduced the concept of inflammatory orbital pseudotumor for patients with a clinical presentation of an orbital tumor, and recognized a subset of patients in whom surgery and histopathology revealed a mass composed of chronic nonspecific inflammation with lymphoid follicles. Unfortunately, the term pseudotumor became accepted as a working diagnosis for patients with orbital inflammatory syndrome and unexplained space-occupying lesions. In the 1980s, orbital pseudotumor
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