三. Pathogenic factor A Susceptibility gene: HLA-DR3 A Environmental Factors ultraviolet light food c drugs hydralazine procainamide D-penicillamine Sex hormone Infections agents三. Pathogenic factor ▲ Susceptibility gene：HLA-DR3 ▲ Environmental Factors： a. ultraviolet light b. food c. drugs hydralazine procainamide D-penicillamine ▲ Sex hormone ▲ Infections agents