Myasthenia gravis after the third dose of human papillomavirus 9-valent vaccine: A case report.

Human papillomavirus (HPV) infection is the main cause of cervical cancer. HPV vaccination is considered an effective way to prevent cervical cancer. Although the vast majority of people experience no obvious adverse reactions after being vaccinated with HPV vaccine, the continuous monitoring of adverse events following immunization is important. Herein, we report the case of a previously healthy young woman who developed unilateral extraocular muscle palsy after receiving the third dose of the Gardasil HPV 9-valent vaccine (9vHPV) and was diagnosed with myasthenia gravis (MG). The patient developed swelling of the left eye on the 3rd day after vaccination and ptosis of the left eyelid on the 18th day after vaccination. She was treated with oral pyridostigmine and methylprednisolone. Her symptoms began to improve after 2 weeks of treatment and resolved completely after 3 weeks. After excluding other possible causes and considering the close temporal relationship between the timing of the 9vHPV vaccination and the onset of symptoms, 9vHPV appears to have triggered MG. To our knowledge, this is the first documented case report of 9vHPV-associated MG in China. Although ocular MG may be a rare adverse event after vaccination with 9vHPV, there is currently no direct evidence establishing a causal relationship; therefore, the safety of 9vHPV remains unquestioned.