rs1142345
A SNP in the TPMT gene on chromosome 6. Its most notable genotype is C;C: possibly incapable of detoxifying certain drugs
- Gene
- TPMT
- Location
- Chr 618,130,687 (GRCh38)
- Highest magnitude
- 3.5Important
- Tested on
- 23andMe, AncestryDNA
- Minor allele frequency
- 5%
Genotypes
Plus strand, as in 23andMe and AncestryDNA files.
- T;TGoodcommon in clinvar
- C;TBadTPMT*3C . impaired drug metabolism
- C;CMost notableBadpossibly incapable of detoxifying certain drugs
SNPedia records rs1142345 on the minus strand: (A;A), (A;G), (G;G). Magnitude rates how notable a genotype is from 0 to 10, not how risky it is.
Frequency
Share of each genotype in 11 HapMap populations.
- AverageT;T 92% C;T 8% C;C <1%
- European ancestry (Utah)T;T 95% C;T 5% C;C 0%
- Han Chinese (Beijing)T;T 99% C;T 2% C;C 0%
- Japanese (Tokyo)T;T 95% C;T 5% C;C 0%
- Yoruba (Nigeria)T;T 92% C;T 8% C;C 0%
- African ancestry (Southwest US)T;T 84% C;T 16% C;C 0%
- Chinese (Denver)T;T 95% C;T 6% C;C 0%
- Gujarati IndianT;T 95% C;T 5% C;C 0%
- Luhya (Kenya)T;T 79% C;T 19% C;C 2%
- Mexican ancestry (Los Angeles)T;T 86% C;T 10% C;C 3%
- Maasai (Kenya)T;T 96% C;T 5% C;C 0%
- TuscanT;T 97% C;T 3% C;C 0%
Related
Conditions, medicines and genes
Other TPMT SNPs
- rs1800460T;Tincapable of detoxifying byproducts of certain drugsImportant
- rs1800462G;Gincapable of detoxifying certain drugsImportant
- rs1800584T;TTPMT*4A homozygote; likely issues detoxifying certain drugsImportant
- rs56161402T;TTPMT*8 homozygote; likely issues detoxifying certain drugsWorth knowing
- rs2842951C;Ccommon in complete genomicsTypical
Notes
From SNPedia
Show notes, about 200 words
rs1142345 is a SNP in the TPMT gene, potentially encoding a variant incapable of detoxifying byproducts of certain antineoplastic and immunosuppressant drugs. In general, individuals must have two nonfunctioning TPMT alleles for the toxicity to be pronounced. The risk allele for this SNP is rs1142345(G), and when it is the only variant in the TPMT gene, it encodes the TPMT*3C allele. While still rare, it is more common in African-Americans (2.4% of all alleles) than in Caucasians. Note that if the same allele also carries the rs1800460(A) SNP, the allele is actually a TPMT*3A allele (OMIM). The medicine 6-Mercaptopurine is metabolized by TPMT. Individual differences in TPMT activity associated with this SNP are now used to determine appropriate dosage range and interval for treatment. 23andMe blog hearing loss linked to a chemotherapy drug named Cisplatin. wikipedia thiopurine drugs metabolized by TPMT include azathioprine, mercaptopurine, and thioguanine
C;C
poor drug metabolism of some medications. potentially encoding a variant incapable of detoxifying byproducts of certain antineoplastic and immunosuppressant drugs. http://blog.23andme.com/health-traits/do-you-know-how-youll-respond-to-thiopurine-medications/
Source and license
Adapted from rs1142345 on SNPedia, using a snapshot taken October 16, 2026. SNPedia content is shared under CC BY-NC-SA 3.0 US, and this page is shared under the same license.
SNPedia is a community-edited wiki. Its entries can be incomplete, out of date or wrong, and nothing here is a diagnosis or medical advice. Magnitude is a community rating of how interesting a genotype is, not a risk score.