Skip to content
Use your HSA or FSA funds

Gene

TPMT

thiopurine S-methyltransferase

Summary

Cytogenetic location
6p22.3
Coordinates
Chromosome 6: 18,128,311–18,155,077 (GRCh38)
Exons
9 exons across 26.8 kb
Protein
245 amino acids
MANE Select transcript
ENST00000309983.5NM_000367.5
Locus type
gene with protein product
  • Very high
  • Confident
  • Low
  • Very low

Reference genomeGRCh38

Positions on gene and variant pages follow this choice, in this browser.

TPMT and medicines

  • Thiopurine methylation

    Pharmacogenomics

    TPMT methylates thiopurine drugs into inactive metabolites. Low activity diverts the drug toward bone marrow, where it can cause severe, sometimes life-threatening myelosuppression.

    • Relevant before starting azathioprine, mercaptopurine or thioguanine for IBD, autoimmune disease, transplant, or leukaemia.
    • Read alongside NUDT15 — the two genes independently shape thiopurine tolerance.

    Alleles the report reads

    • *2No function
    • *3BNo function
    • *1Normal function
    • *3CNo function
    • *3ANo function

    Results CPIC describes

    • Possible Intermediate Metabolizer
    • Intermediate Metabolizer
    • Indeterminate
    • Normal Metabolizer
    • Poor Metabolizer
    MedicineCPIC levelGuideline
    azathioprineATPMT, NUDT15 and Thiopurines
    mercaptopurineATPMT, NUDT15 and Thiopurines
    thioguanineATPMT, NUDT15 and Thiopurines

    Calls *2, *3B and *3C, which together account for most TPMT deficiency. *3B and *3C carried together are assumed to be *3A in cis (the CPIC convention for unphased data); rarer alleles are not assessed and enzyme-activity testing remains the clinical standard.

How TPMT is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Stretches short reads find hard
Chromosome 6, with a bracket where TPMT sits. TPMT and 6 genes near it on chromosome 6, from 17,641,694 to 18,641,693.Chromosome 66p22.3p25.3p25.2p25.1p24.3p24.2p24.1p23p22.3p22.2p22.1p21.33p21.32p21.31p21.2p21.1p12.3p12.2p12.1p11.2p11.1q11.1q11.2q12q13q14.1q14.2q14.3q15q16.1q16.2q16.3q21q22.1q22.2q22.31q22.32q22.33q23.1q23.2q23.3q24.1q24.2q24.3q25.1q25.2q25.3q26q2717.8 Mb18 Mb18.2 Mb18.4 Mb18.6 MbNUP153: 17,614,696–17,706,942, reverse strandNUP153KIF13A: 17,758,198–17,988,274, reverse strandKIF13ANHLRC1: 18,120,440–18,122,677, reverse strandNHLRC1TPMT: 18,128,311–18,155,077, reverse strandTPMTKDM1B: 18,155,293–18,224,495, forward strandKDM1BDEK: 18,223,860–18,265,997, reverse strandDEKRNF144B: 18,307,066–18,468,874, forward strandRNF144BDiagram of TPMT: 9 exons on the reverse strand of chromosome 6Exon 9: 18,128,311–18,130,780, 2,470 basesExon 8: 18,132,133–18,132,177, 45 basesExon 7: 18,133,804–18,133,889, 86 basesExon 6: 18,138,963–18,139,037, 75 basesExon 5: 18,139,665–18,139,717, 53 basesExon 4: 18,143,596–18,143,728, 133 basesExon 3: 18,147,823–18,147,915, 93 basesExon 2: 18,148,988–18,149,171, 184 basesExon 1: 18,155,033–18,155,077, 45 bases9876543215′3′

Exons of the gene's MANE Select transcript (release v1.5), from NCBI and EMBL-EBI, on the GRCh38 reference genome.

Chromosome bands from UCSC's GRCh38 ideogram (2022-10-29).

Nearby genes from Ensembl release 116, on GRCh38.

Exons make up 3.2 kb of the gene's 26.8 kb; 738 of those bases code for the protein.

Where this comes from

  • HGNC: the gene's symbol, name, other symbols and location.
  • MANE Select v1.5, from NCBI and EMBL-EBI: the transcript, its exons and coding sequence.
  • CPIC and PharmGKB: the alleles, results and medicines.
  • The Human Phenotype Ontology, release 2026-09-01: the traits linked to the gene. Find out more at hpo.jax.org.

Cite this page

APA

Dante Labs. (n.d.). TPMT gene: thiopurine S-methyltransferase. Retrieved 16 October 2026, from https://dantelabs.com/genes/tpmt

Vancouver

Dante Labs. TPMT gene: thiopurine S-methyltransferase [Internet]. [cited 16 October 2026]. Available from: https://dantelabs.com/genes/tpmt

One test. A lifetime of answers.

From $449Free shipping · Results in 6–8 weeks

Get my Genome Test