Abstract
Isolated superior oblique myositis is a rare variant of idiopathic orbital myositis. We are reporting for the first time the case of a 19-year-old woman who had isolated superior oblique myositis with sinusitis that mimics a subperiosteal abscess. Despite the typical history of upper respiratory tract infection and laboratory test results and initial radiological findings suggestive of orbital cellulitis secondary to sinusitis, the initial response to systemic steroid with subsequent imaging changes and the relapse after cessation of steroid therapy helped us reach the diagnosis.