RESUMO
Objective: Orbital myositis is a rare clinical condition that involves idiopathic inflammation mostly of extraocular muscles. The purpose of this study was to present a diagnostic and treatment plan of orbital myositis. Methods: A 60-year-old female presented with decreased visual acuity on her left eye, ocular hypertension, restricted and painful left abduction, diplopia, swollen eyelids, and orbital discomfort. MRI, as well as ultrasound, showed enlargement in width of medial rectus muscle. After other diagnoses were excluded, the diagnosis of left orbital myositis was established. Results: She was started on systemic corticosteroid treatment, but each time the steroid dose was tapered she experienced a relapse. Immunosuppressive therapy was introduced and the steroid dose was gradually tapered and excluded. One year after immunosuppressive therapy, the clinical findings improved. Conclusion: The diagnosis of orbital myositis requires detailed examination, laboratory testing and MRI scans of the orbits in order to exclude other diseases with similar clinical findings. The first line treatment option is systemic corticosteroid therapy with additional immunosuppressive therapy if needed. Abbreviations: MRI = magnetic resonance imaging, BCVA = best corrected visual acuity, ENT = ear, nose, throat specialist, CBC = complete blood count, WBC = white blood cell, ESR = erythrocyte sedimentation rate, CRP = C reactive protein, HM = hand motion, TED = thyroid eye disease, SLE = systemic lupus erythematosus, ECG = electrocardiogram, CT = computed tomography.