Serological analysis to investigate possible autoimmune diseases revealed a borderline elevated ANA titre of 1:160 in one patient with paranoid schizophrenia, while the other serological tests (extractable nuclear antigen antibodies (ENA), rheumatoid factor, anti-neutrophil cytoplasmic antibodies (ANCA), anti-thyroid antibodies, antineuronal antibodies (NMDA, CASPR2, LGI1. Here, CNTNAP2 is linked to schizophrenia.