More Than Meets the Eye: Idiopathic Orbital Inflammation Mimicking Orbital Cellulitis

An 18-year-old female presented with left eye periorbital swelling, erythema, and pain for three days. Computed tomographic images showed swelling of the medial rectus muscle, and she was diagnosed with orbital cellulitis and initiated on empiric antibiotics. Over the next 48 hours, she did not clinically improve, resulting in an MRI and further workup of infectious, oncologic, endocrinologic, and rheumatologic etiologies was unrevealing and ruled-out malignancy, sarcoidosis, Wegner's, and thyroid eye disease. Given the negative workup, the presentation was determined to be consistent with idiopathic orbital inflammation (orbital myositis variant) via a diagnosis of exclusion. Therefore, the patient was empirically treated with intravenous steroids that produced pronounced improvement within 24 hours. The patient was discharged in improved condition with a prednisone taper and rheumatology follow-up. Idiopathic orbital inflammation is a rare diagnosis of exclusion in pediatrics that merits prompt consideration and work-up if treatment for orbital cellulitis does not progress as expected.