rs10127939

A SNP in the FCGR3A gene on chromosome 1. Its most notable genotype is T;T: immunodeficiency, but not for 23andMe users

Gene
FCGR3A
Location
Chr 1161,548,543 (GRCh38)
Highest magnitude
1.0Minor
Tested on
23andMe, AncestryDNA, FamilyTreeDNA
Minor allele frequency
4%

Genotypes

Plus strand, as in 23andMe and AncestryDNA files.

  1. T;TMost notableBadimmunodeficiency, but not for 23andMe usersMinor · 1.093% of people
  2. A;AGoodcommon in clinvarTypical · 0.0<1% of people

SNPedia records rs10127939 on the minus strand: (A;A), (T;T). 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.

  • AverageT;T 93% A;A <1%
  • European ancestry (Utah)T;T 90% A;A 0%
  • Han Chinese (Beijing)T;T 100% A;A 0%
  • Japanese (Tokyo)T;T 100% A;A 0%
  • Yoruba (Nigeria)T;T 83% A;A 2%

Other FCGR3A SNPs

All FCGR3A SNPs

Notes

From SNPedia

Notes

T;T

For 23andMe users, this is the normal form, you can safely ignore it. However when oriented to current versions of dbSNP, this is a very rare genotype and linked to immunodeficiency This rare homozygous genotype has been reported to be the basis of primary immunodeficiency-20 in several publications. However, due to the orientation issues (and confusion) connected to A/T ambiguous flips and the assignment of this SNP to the reverse strand in dbSNP in at least some versions of dbSNP, be aware that this may be a false assignment if you see it in your Promethease report and it should be independently checked/verified.

Source and license

Adapted from rs10127939 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 Its entries can be incomplete, out of date or wrong, and nothing here is a diagnosis or medical advice.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.