[Ocular myositis. A rare differential diagnosis of sinus-induced orbital complications].

Orbital myositis is an uncommon subgroup of the nonspecific orbital inflammatory syndromes (previously termed orbital pseudotumor) and presents with eyelid swelling and redness, conjunctival chemosis, pain, proptosis, and diplopia. The disease is to date of unknown origin; autoimmune processes are suspected for the etiology. In the case of an otherwise healthy young male patient (age 28 years), the coexistence of chronic sinusitis primarily led to the diagnosis of sinugen orbital cellulitis. Despite antibiotic drug administration and surgical drainage of the paranasal sinuses the symptoms persisted. A second computed tomography revealed fusiform, inflammatory enlargement of the m. rectus lateralis. This muscle showed a restrictive paresis so that initially the m. rectus 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 orbital myositis is significant because corticosteroids are contraindicated for orbital cellulitis whereas they remain the therapy of choice for orbital myositis.