FREQUENCIES OF HLA-A24 AND HLA-DR4-DQ8 ARE INCREASED AND THAT OF HLA-B BLANK IS DECREASED IN CHRONIC TOXIC OIL SYNDROME

SUMMARY The cause of toxic oil syndrome (TOS) has not yet been definitively determined, but some genetic susceptibility factors (certain HLA antigens and female sex) have been identified in 236 patients. Similarities with genetic factors for scleroderma and hydralazine‐induced lupus (i.e. in TOS female sex and HLA‐A24, Pcorrected= 0.00001 and DR4, Pcorrected= 0.04, respectively) may provide a clue to the responsible xenobiotic and its pathogenesis, and may also help in understanding the basis of the related eosinophilia‐myalgia syndrome associated with tryptophan ingestion. In this paper it is also established that a human class I antigen (HLA‐A24) and, independently, an HLA class II haplotype (DR4‐DQ8, Pcorrected= 0.04) and arginine 52 in the α‐DQ chains (Pcorrected= 0.03) are associated with TOS susceptibility, similarly to insulin‐dependent diabetes. This further supports the classification of TOS as an autoimmune disease. Also, the increased frequency of a particular set of low‐frequency HLA class I antigens in chronic TOS patients (i.e. B27, B37, B38 and B49) and the probable decrease in the frequency of HLA‐B homozygotes in surviving patients (Pcorrected= 0.008) may provide an objective model to explain the maintenance of the HLA polymorphism: less frequent HLA alleles may be more advantageous in the event of unexpected human contact with unusual xenobiotics (not only microbes); however, other mechanisms working together to preserve and generate HLA polymorphism may coexist.