Immunogenetic risk and protective factors for the development of L‐tryptophan–associated eosinophilia–myalgia syndrome and associated symptoms

Objective To assess L‐tryptophan (LT) dose, age, sex, and immunogenetic markers as possible risk or protective factors for the development of LT‐associated eosinophilia–myalgia syndrome (EMS) and related clinical findings. Methods HLA–DRB1 and DQA1 allele typing and Gm/Km phenotyping were performed on a cohort of 94 white subjects with documented LT ingestion and standardized evaluations. Multivariate analyses compared LT dose, age, sex, and alleles among groups of subjects who ingested LT and subsequently developed surveillance criteria for EMS, developed EMS or characteristic features of EMS (EMS spectrum disorder), or developed no features of EMS (unaffected). Results Considering all sources of LT, higher LT dose (odds ratio [OR] 1.4, 95% confidence interval [95% CI] 1.1–1.8), age >45 years (OR 3.0, 95% CI 1.0–8.8), and HLA–DRB1*03 (OR 3.9, 95% CI 1.2–15.2), DRB1*04 (OR 3.9, 95% CI 1.1–16.4), and DQA1*0601 (OR 13.7, 95% CI 1.3–1.8) were risk factors for the development of EMS, whereas DRB1*07 (OR 0.12, 95% CI 0.02–0.48) and DQA1*0501 (OR 0.23, 95% CI 0.05–0.85) were protective. Similar risk and protective factors were seen for developing EMS following ingestion of implicated LT, except that DRB1*03 was not a risk factor and DQA1*0201 was an additional protective factor. EMS spectrum disorder also showed similar findings, but with DRB1*04 being a risk factor and DRB1*07 and DQA1*0201 being protective. There were no differences in sex distribution, Gm/Km allotypes, or Gm/Km phenotypes among any groups. Conclusion In addition to the xenobiotic dose and subject age, polymorphisms in immune response genes may underlie the development of certain xenobiotic‐induced immune‐mediated disorders, and these findings may have implications for future related epidemics.