An occupational disease: a severe hypersensitivity reaction some solvent-exposed workers develop to trichloroethylene, an industrial degreasing agent. A study of Chinese factory workers found a genetic risk score at MICA explaining over 20% of the disease's variance — large for this catalogue — with real relevance to pre-employment genetic screening for this specific job risk.
Trichloroethylene (TCE) is an industrial solvent used widely in metal degreasing and electronics manufacturing. In a small proportion of workers exposed to it, TCE triggers a severe hypersensitivity reaction — skin eruption, fever, and organ involvement including hepatitis — that can be fatal if exposure continues without recognition. It is an occupational disease, specific to workers handling this solvent, not something the general population is exposed to.
Dai et al. 2015 ran a genome-wide association study in Chinese factory workers: 174 cases of the syndrome against 1,761 TCE-tolerant controls — people with comparable solvent exposure who did not develop the reaction. That comparison group matters: it isolates a genetic susceptibility effect from exposure itself, rather than comparing exposed cases against an unexposed general population.
The study identified two independent variants — one at MICA (the variant on this page) and one between HLA-B and MICA. A genetic risk score combining both explains at least 20.9% of the disease's variance, with up to a 32.5-fold difference in risk between people at the two ends of that score.
Most variants on this catalogue shift risk by a small amount. This one does not, and the difference is not a fluke of a small study — it reflects HLA and HLA-adjacent genetics, which is disproportionately represented among the largest-effect variants in human genetics generally (drug hypersensitivity reactions are a well-known example). A genetic risk score this predictive is why the paper's authors discuss pre-exposure screening as a real, practical possibility for this specific occupational risk, rather than a hypothetical one.
This is an occupational disease. It matters to people working with trichloroethylene or considering that kind of role, and to occupational health programs at facilities that use it — not to the general population, who are not meaningfully exposed to TCE at the levels that trigger this reaction.
The predictive strength found here (a risk score explaining over a fifth of disease variance) is genuinely large for a genetic finding, and it is specific to a population with defined occupational TCE exposure studied in China. Whether the same score performs as well in other populations or exposure settings has not been established on this page's evidence alone.
MICA and the broader HLA region show up across this catalogue in other immune-related contexts — a shared theme of genes involved in presenting or recognising foreign material to the immune system, here triggered by a chemical rather than an infection.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Trichloroethylene-Induced Hypersensitivity Syndrome comes down to these specific, well-studied positions — not a diagnosis.
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Trichloroethylene-Induced Hypersensitivity Syndrome. MyGeneLog™. https://www.mygenelog.com/conditions/trichloroethylene-hypersensitivity-syndrome
No. This is specifically a reaction to trichloroethylene exposure in an occupational setting — metal degreasing and electronics manufacturing are the main contexts. The general population is not meaningfully exposed to TCE at the levels that trigger this syndrome.
It involves the HLA region, which is disproportionately represented among the largest-effect findings in human genetics — drug and chemical hypersensitivity reactions are a well-known example. Most variants shift risk by a small amount; this one, combined with a second nearby variant, explains over a fifth of who develops the syndrome among exposed workers.
The paper's authors discuss it as a real possibility given the score's predictive strength, though this page does not confirm whether any employer or occupational health program has implemented it. It would be a decision for occupational medicine, not something this page recommends.
It is part of the MHC class I-related gene family, involved in presenting signals to the immune system. In this context, the risk variant is associated with an abnormal hypersensitivity reaction to a chemical exposure rather than its everyday immune role.
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