Established individual neurodevelopmental, neurodegenerative, and autoimmune disease susceptibility genes such as DRD2, APOE, ABCA7, TGFB1, TERT, POMC, HDAC5, WNT1, CARD9, LRP5, NRXN2, SHANK3&1, HBA, TH, PRRT2 and IGF2 are rich in C + G, whereas SNCA, PTPN22, LRRK2, TLR1, and PTH are rich in A + U nucleobases. The gene discussed is PTPN22; the disease is autoimmune disease.