rs116855232
Thiopurine sensitivity, NUDT15
What this position does
Azathioprine and mercaptopurine are used in inflammatory bowel disease, transplant medicine and leukaemia. NUDT15 variants cause severe bone-marrow suppression at normal doses, and they are the main cause of this in East Asian populations, where TPMT testing alone misses it.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version CC | Normal function Normal NUDT15 activity at this position. |
| One copy CT | Intermediate metaboliser A reduced starting dose of thiopurine drugs is recommended by guideline. |
| Two copies TT | Poor metaboliser Drastically reduced dosing is required. Standard doses carry a serious risk of bone-marrow suppression. |
How common each version is
| Ancestry group | T (the effect version) | |
|---|---|---|
| African | 0.1% | |
| American | 4.5% | |
| East Asian | 9.5% | |
| European | 0.2% | |
| South Asian | 7.0% |
1000 Genomes Project phase 3, via Ensembl, retrieved 2026-09-23. These groupings are coarse and flatten a great deal of internal diversity, particularly within Africa. A variant being common somewhere tells you where a piece of your ancestry probably comes from, and nothing else.
How many people carry each result
| Ancestry group | CC | CT | TT |
|---|---|---|---|
| African | 660 / 661 | 1 / 661 | 0 / 661 |
| European | 501 / 503 | 2 / 503 | 0 / 503 |
| East Asian | 416 / 504 | 80 / 504 | 8 / 504 |
| South Asian | 424 / 489 | 62 / 489 | 3 / 489 |
| American | 318 / 347 | 27 / 347 | 2 / 347 |
Counts of people, not modelled frequencies: every one of the 2,504 individuals sequenced by the 1000 Genomes Project phase 3, tallied by the genotype they carry. Deriving these from allele frequencies instead would assume random mating inside each group and undercount the homozygotes.
How to find out which you have
If you have taken a test with 23andMe, AncestryDNA, MyHeritage, Family Tree DNA, TellMeGen or Living DNA, this position is very likely already in the raw data file they gave you. You do not need another test.
One thing to watch if you look it up by hand: testing companies report some positions from one DNA strand and some from the other, and the file does not say which. Read the letters as they appear and you will get the opposite of the truth for some positions. Sequencings resolves that automatically.
Source
CPIC Guideline for Thiopurines and TPMT and NUDT15
Coordinates and allele pair verified against Ensembl GRCh37. Direction of effect verified against VEP protein consequences or 1000 Genomes population frequency. Category: Medicine response.
Where this fits
Common questions
What is rs116855232?
rs116855232 is a position in the NUDT15 gene on chromosome 13. Azathioprine and mercaptopurine are used in inflammatory bowel disease, transplant medicine and leukaemia. NUDT15 variants cause severe bone-marrow suppression at normal doses, and they are the main cause of this in East Asian populations, where TPMT testing alone misses it.
What does it mean if I have TT at rs116855232?
Poor metaboliser. Drastically reduced dosing is required. Standard doses carry a serious risk of bone-marrow suppression.
What does it mean if I have CC at rs116855232?
Normal function. Normal NUDT15 activity at this position.
How do I find out my rs116855232 genotype?
If you have taken a home DNA test, this position is very likely in the raw data file you were given. Sequencings reads that file in your browser without uploading it, and resolves which DNA strand each position was reported from, which is the step most manual lookups get wrong.
This is reference information, not medical advice, and not a diagnosis. See the medical disclaimer. Category: Medicine response.