Idiopathic Orbital Myositis Revisited

Abstract

Purpose of ReviewTo review current knowledge regarding idiopathic orbital myositis. Recent Findings Recent publications have focused on possible causes of orbital myositis and the process to reach a diagnosis of idiopathic orbital myositis. With inflamed and enlarged extraocular muscles, features to distinguish between competing diagnostic possibilities are based on imaging in the context of history and clinical signs. Idiopathic orbital myositis is characterized by the clinical triad of acute onset of orbital pain exacerbated on eye movement, double vision, and redness or swelling of the eyelids or conjunctiva, along with the radiological finding of homogeneous, fusiform enlargement of one or more extraocular muscles. In atypical or inconclusive clinico-radiological findings for a diagnosis of idiopathic orbital myositis, or where the clinical behavior changes or fails to respond to corticosteroid treatment, a systemic and oncologic work-up and muscle biopsy are warranted to exclude specific local or systemic disease as cause of the inflamed and enlarged muscle. Summary As our understanding of idiopathic orbital myositis evolves, the diagnostic focus is shifting toward earlier identification of underlying local or systemic disease through systemic work-up and muscle biopsy.

Recurrent inferior oblique myositis and its outcomes

“…IOM is the least common type of orbital myositis, with only four other case reports describing the condition. Idiopathic orbital myositis can affect any of the EOMs, with rectus muscle involvement being more frequently reported than that of the oblique muscles 1. In a series of 119 patients, the relative frequency of involvement of each EOM was: medial rectus (32.0%), lateral rectus (25.9%), superior rectus (23.5%), inferior rectus (11.9%), superior oblique (3.7%) and inferior oblique (3.1%) 3 4…”

“…The standard radiological findings of orbital myositis are homogenous, fusiform enlargement and enhancement of the affected muscle 1. On orbital MRI, 100% (n=4) reported thickening and enhancement of the inferior oblique muscle.…”

“…One report described concurrent methotrexate usage, although that patient returned after 10 months 6. Factors that contribute to disease recurrence include undertreatment, treatment duration and compliance 1…”

“…The diagnosis of idiopathic orbital myositis requires the exclusion of any identifiable local or systemic cause, including drug reactions, systemic inflammatory, infective and autoimmune disease, paraneoplastic immune phenomena and poststreptococcal pharyngeal infection 1…”

“…Orbital myositis, characterised by localised inflammation of the extraocular muscles (EOMs), most commonly manifests as the idiopathic type. Although well-recognised, the pathogenesis remains elusive 1. Inferior oblique involvement is the least common presentation of idiopathic orbital myositis with a reported incidence rate of 0%–4.3% and few documented cases 2–4.…”