{{Rsnum
|rsid=121964972
|Chromosome=21
|Orientation=minus
|geno1=(C;C)
|geno2=(C;T)
|geno3=(T;T)
|Gene=CBS
|position=43060528
|Assembly=GRCh38
|GenomeBuild=38.1
|dbSNPBuild=141
|Gene_s=CBS
}}307S (common in Irish populations) is associated with a more severe form of Homocystinuria and is unresponsive to pyridoxine (vitamin B6) treatment.

{{omim
|id=613381
|rsnum=121964972
|variant=0015
}}{{ClinVar
|rsid=121964972
|Reversed=1
|FwdREF=C
|FwdALT=T
|REF=G
|ALT=A
|RSPOS=44480638
|CHROM=21
|dbSNPBuildID=133
|SSR=0
|SAO=1
|VP=0x050260000000000002110100
|GENEINFO=CBS:875
|GENE_NAME=CBS
|GENE_ID=875
|WGT=0
|VC=SNV
|CLNALLE=1
|CLNHGVS=NC_000021.8:g.44480638G>A
|CLNSRC=Emory University; OMIM Allelic Variant
|CLNORIGIN=1
|CLNSRCID=8549; 613381.0015
|CLNSIG=5
|CLNCUI=CN068393
|CLNDBN=Homocystinuria, pyridoxine-nonresponsive; not provided
|Disease=Homocystinuria; not provided
|CLNACC=RCV000000154.1; RCV000078106.1
|Tags=RV;PM;S3D;OTHERKG;LSD;OM
|CLNDSDB=MedGen
|CLNDSDBID=CN068393
}}