Orbital myositis. A rare differential diagnosis of sinugenic orbital complications

Orbital myositis is an uncommon subgroup of the nonspecific orbital inflamm atory syndromes (previously termed orbital pseudotumor) and presents with e yelid swelling and redness, conjunctival chemosis, pain, proptosis, and dip lopia. The disease is to date of unknown origin; autoimmune processes are s uspected for the etiology. In the case of an otherwise healthy young male patient (age 28 years),the c oexistence of chronic sinusitis primarily led to the diagnosis of sinugen o rbital cellulitis. Despite antibiotic drug administration and surgical drai nage of the paranasal sinuses the symptoms persisted. A second computed tom ography revealed fusiform, inflammatory enlargement of the m. rectus latera lis. This muscle showed a restrictive paresis so that initially the m. rect us medialis was suspected to be paretic. The patient responded dramatically to administration of prednisolone within 2 days. The differential diagnosis between a sinugen orbital complication and orbit al myositis is significant because corticosteroids are contraindicated for orbital cellulitis whereas they remain the therapy of choice for orbital my ositis.