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TPMT

From SNPedia

is agene
is mentioned by
Full namethiopurine S-methyltransferase
EntrezGene7172
PheGenI7172
VariationViewer7172
ClinVarTPMT
GeneCardsTPMT
dbSNP7172
SADR7172
HugeNav7172
wikipediaTPMT
googleTPMT
gopubmedTPMT
EVSTPMT
HEFalMpTPMT
MyGene2TPMT
23andMeTPMT
UniProtP51580
EnsemblENSG00000137364
OMIM187680
# SNPs9
 Max MagnitudeChromosome positionSummary
rs11423453.518,130,687
rs1220119918,139,571
rs18004603.518,138,997
rs18004623.518,143,724
rs18005843.518,130,781
rs2842951018,135,452
rs56019966018,139,041
rs561614022.518,130,762known as R215H, encoding the TPMT*8 allele
rs74423290018,133,884
TPMT encodes a gene best known for helping to break down potentially toxic products of the antineoplastic agents 6-mercaptopurine (6MP) and 6-thioguanine (6TG), as well as the immunosuppressant azathioprine (AZA). Individuals homozygous for two nonfunctional TPMT variants are at high risk for toxic side effects if in the course of their treatment they are treated with such drugs.

The most common nonfunctional TPMT alleles, as defined by certain SNPs, are:

  • rs1800460, known as 460A>G or A154T, potentially encoding the TPMT*3A allele;
  • rs1142345, known as 719A>G or Y240C, potentially encoding the TPMT*3C allele;
  • rs1800462, known as A80P, encoding the TPMT*2 allele
  • rs56161402, known as R215H, encoding the TPMT*8 allele
  • rs1800584, encoding the TPMT*4A allele

Although these alleles are all relatively rare, they do vary in frequency between ethnic populations; for example, the most common TPMT variant in African-Americans is Y240C (2-3% of all alleles; but 50% of all variants), whereas the most common variant in Caucasians is A154T (5% of all alleles).

More complete details on effects of variations of this gene on drug metabolism are provided PharmGKB.