The c.1837C>T (p.Arg613Ter) (NM_000215.4) variant in JAK3 is a nonsense variant predicted to cause a premature stop codon in biologically-relevant-exon 14/24 leading to nonsense mediated decay in a gene in which loss-of-function is an established disease mechanism (PVS1). The filtering allele frequency (the upper threshold of the 95% CI of 3/113712) of the c.1837C>T variant in JAK3 is 0.000007010 for European (non-Finnish) chromosomes by gnomAD 2.1.1, which is lower than the ClinGen SCID VCEP threshold (<0.000115) for PM2_Supporting, and therefore meets this criterion (PM2_Supporting). At least one patient with this variant displayed: * Diagnostic criteria for SCID/Leaky SCID/Omenn syndrome met (0.5pt), *T-B+NK- lymphocyte subset profile (0.5pt), and *SCID phenotype corrected by JAK3 gene therapy WITHOUT CNV testing performed (1pt), totalizing 2 points, which is highly specific for SCID (PP4_moderate. PMID: 26321643). This variant has been detected in at least one individual with SCID, which is homozygous for the variant (0.5 pt) (PM3_Supporting. PMID: 26321643). One additional patient was found on Clinvar; however, the affected status is unknown. In summary, this variant meets the criteria to be classified as Pathogenic for autosomal recessive SCID based on the ACMG/AMP criteria applied, as specified by the ClinGen SCID VCEP. Criteria applied: PVS1, PP4_moderate, PM2_supporting and PM3_supporting. (VCEP specifications version 1).