Unilateral Migratory Relapsing Orbital Myositis While on Immunosuppressant Therapy: An Uncommon Entity

A young healthy female presented with acute onset left ocular pain, restricted ocular motility, and binocular diplopia. CT imaging showed left lateral rectus myositis that resolved with oral corticosteroids. Two sequential relapses occurred subsequently involving the superior rectus-levator complex followed by the medial rectus. Biopsy revealed orbital inflammatory disease with lymphocytic vasculitis. Detailed systemic work up was normal. The second relapse was seen while on long-term oral methotrexate although initial disease remission had been achieved with the same drug. A changeover to oral azathioprine was able to achieve disease remission after the second relapse. All relapses involved the same side and the contralateral orbit was not affected. This report presents the curious phenomenon of unilateral migratory relapsing orbital myositis of unknown cause that recurred even while on immunosuppressant therapy. It highlights the unpredictable nature of this uncommon entity and the challenges faced in managing such cases.