Pathogenic factor A Susceptibility gene: HLA-DR3 A Environmental Factors a. 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