Acute Unilateral Ptosis and Myositis Following the H1N1 Influenza Vaccine.

The authors present a rare case of sudden onset unilateral complete ptosis occurring hours after administration of the H1N1 influenza vaccine. A complete workup for autoimmune and neurological disease was negative. MRI of the orbits demonstrated unilateral orbital myositis involving the left superior rectus/levator complex, superior oblique, and medial rectus muscles. Ptosis resolved spontaneously over 2 months without intervention. An autoimmune mechanism may explain rare cases of orbital myositis following administration of the H1N1 influenza vaccination.