His routine laboratory tests (a full blood count, erythrocyte sedimentation rate, platelets, creatinine, blood urea nitrogen, glucose, lipids, and transaminases) were normal, his thyroid hormone values and anti-thyroid peroxidase (TPO) antibody level, anti-neutrophil cytoplasmic antibodies (ANCA), cellular and humoral immune indexes were normal, and his HIV and syphilis serological test results were negative. Here, TPO is linked to syphilis.