Antiphospholipid antibodies are a major risk factor of juvenile cerebral infarction; in addition, they can cause major arterial stenosis or occlusion. We report a case of a 32-year-old man who had been diagnosed with systemic lupus erythematosus at the age of 20 years, and was admitted to Shin-Oyama City Hospital, Tochigi, Japan, because of left arm weakness. Cerebral infarction and occlusion of the right internal carotid artery were found. Tests were positive for phosphatidylserine-dependent antiprothrombin antibody, which can be useful for the diagnosis of antiphospholipid syndrome. Phosphatidylserine-dependent antiprothrombin antibody might have the potential to cause thrombosis and vasculitis-like occlusion. [ABSTRACT FROM AUTHOR]