rs1127354

A SNP in the ITPA gene on chromosome 20. Its most notable genotype is A;A: Causative for ITPase deficiency; also, reduces risk of anemia due to ribivarin anti-hepatitis C virus therapy

Gene
ITPA
Location
Chr 203,213,196 (GRCh38)
Highest magnitude
3.2Important
Tested on
23andMe, AncestryDNA
Minor allele frequency
8%

Genotypes

As shown in 23andMe and AncestryDNA files.

  1. A;AMost notableBadCausative for ITPase deficiency; also, reduces risk of anemia due to ribivarin anti-hepatitis C virus therapyImportant · 3.21% of people
  2. A;CBadlower ITPA production; be aware if treated with mercaptopurineWorth knowing · 2.014% of people
  3. C;CGoodcommon in clinvarTypical · 0.085% of people

On SNPedia: (A;A), (A;C), (C;C). Magnitude rates how notable a genotype is from 0 to 10, not how risky it is.

Frequency

Share of each genotype in 4 HapMap populations.

  • AverageA;A 1% A;C 14% C;C 85%
  • European ancestry (Utah)A;A 0% A;C 17% C;C 83%
  • Han Chinese (Beijing)A;A 4% A;C 13% C;C 82%
  • Japanese (Tokyo)A;A 0% A;C 20% C;C 80%
  • Yoruba (Nigeria)A;A 0% A;C 7% C;C 93%

Other ITPA SNPs

All ITPA SNPs

Notes

From SNPedia

Show notes, about 390 words

rs1127354 (Pro32Thr/P32T, 94C>A) is a SNP within the ITPA (Inosine triphosphate pyrophosphatase) gene. (note: rs1127354 supersedes rs41320251) abolishes ITPA activity in homozygous individuals and reduces the activity to 25% in heterozygous subjects, mercaptopurine metabolism (sig. higher methyl mercaptopurine nucleotides levels + higher probability of severe febrile neutropenia in A carriers treated with mercaptopurine) Mutations in the gene encoding the Wnt-signaling component R-spondin 4 (RSPO4) cause autosomal recessive anonychia. Pharmacogenomic studies of the anticancer and immunosuppressive thiopurines mercaptopurine and azathioprine. Investigation of candidate polymorphisms and disease activity in rheumatoid arthritis patients on methotrexate. Variants in the ITPA gene protect against ribavirin-induced hemolytic anemia and decrease the need for ribavirin dose reduction. ITPA gene variant protects against anemia induced by pegylated interferon-alpha and ribavirin therapy for Japanese patients with chronic hepatitis C. Common genetic polymorphism of ITPA gene affects ribavirin-induced anemia and effect of peg-interferon plus ribavirin therapy. Impact of inosine triphosphatase gene variants on the risk of anemia in HIV/hepatitis C virus-coinfected patients treated for chronic hepatitis C. Variants in the ITPA gene protect against ribavirin-induced hemolytic anemia in HIV/HCV-coinfected patients with all HCV genotypes. Efficacy of splenectomy in preventing anemia in patients with recurrent hepatitis C following liver transplantation is not dependent on inosine triphosphate pyrophosphatase genotype. Inosine triphosphatase polymorphisms and ribavirin pharmacokinetics as determinants of ribavirin-associate anemia in patients receiving standard anti-HCV treatment. Association of ITPA gene polymorphisms and the risk of ribavirin-induced anemia in HIV/hepatitis C virus (HCV)-coinfected patients receiving HCV combination therapy. Comparison of three different methods for the evaluation of IL28 and ITPA polymorphisms in patients infected with HCV. Hepatitis C Treatment Side Effects

A;A

Causative for ITPase deficiency; be aware of higher neutropenia risk if treated with mercaptopurine; yet also, reduced risk of anemia when subject to ribivarin-based anti-hepatitis C virus therapy.

A;C

see discussion at rs1127354

Source and license

Adapted from rs1127354 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.