{{Rsnum
|rsid=2824499
|Gene=C21orf91
|Chromosome=21
|position=17806954
|Orientation=plus
|GMAF=0.2511
|Gene_s=C21orf91
|Assembly=GRCh38
|GenomeBuild=38.1
|dbSNPBuild=141
|geno1=(C;C)
|geno2=(C;T)
|geno3=(T;T)
}}{{ population diversity
| geno1=(C;C)
| geno2=(C;T)
| geno3=(T;T)
| CEU | 62.5 | 33.0 | 4.5
| HCB | 42.3 | 46.7 | 10.9
| JPT | 38.9 | 42.5 | 18.6
| YRI | 58.5 | 36.7 | 4.8
| ASW | 64.9 | 33.3 | 1.8
| CHB | 42.3 | 46.7 | 10.9
| CHD | 34.3 | 44.4 | 21.3
| GIH | 64.4 | 31.7 | 4.0
| LWK | 70.9 | 24.5 | 4.5
| MEX | 50.0 | 29.3 | 20.7
| MKK | 84.0 | 16.0 | 0.0
| TSI | 56.9 | 39.2 | 3.9
| HapMapRevision=28
}}{{PMID|22039568|OA=1
}} C21orf91 genotypes correlate with herpes simplex labialis (cold sore) frequency: description of a cold sore susceptibility gene.

{{on chip | 23andMe v1}}
{{on chip | 23andMe v2}}
{{on chip | 23andMe v3}}
{{on chip | 23andMe v4}}
{{on chip | FTDNA2}}
{{on chip | FTDNA}}
{{on chip | HumanOmni1Quad}}
{{on chip | Illumina Human 1M}}