The NM_000448.3:c.1A>G (p.Met1Val) variant in RAG1 is an initiation codon variant that is not expected to result in nonsense-mediated mRNA decay but may cause a truncated protein by using an alternative start codon (Met183). There is one frameshift variant (p.K86VfsX33) that occurs upstream of codon 183, which causes the production of an N-terminally truncated RAG1 with low recombination activity and altered cellular localization (PMIDs 24290284, 11121059, 27301863) (PVS1_Moderate). The gnomAD 2.1.1 Popmax filtering allele frequency of this variant is 0.0001017, which is lower than the SCID VCEP threshold for PM2 (0.000102), and no homozygous individual has been observed in the gnomAD. Therefore it meets this criterion (PM2_Supporting). The variant has been detected in at least four individuals diagnosed with primary immunodeficiency. Patient A, reported by PMID 26186701, was heterozygous for this variant and a p.R737H variant (not curated by the SCID-VCEP), 0 pt. The other three individuals were reported in ClinVar entries without the information of the second allele, and in all three entries, the variant was classified as Uncertain Significance (Illumina Laboratory Services, SCV000371654.2; Illumina Laboratory Services, SCV000371655.2; Invitae, SCV001230493.3). The reported patient information is not sufficient to meet PM3 or PP4 criteria. Due to insufficient evidence, this variant is classified as a variant of uncertain significance for SCID based on the ACMG/AMP criteria applied, as specified by the ClinGen SCID-VCEP: PVS1_Moderate, PM2_Supporting (SCID VCEP specifications version 1.0).