NM_000051.4:c.5983G>T (p.Glu1995Ter) is a nonsense variant in exon 40 of 63 of ATM, a gene where loss of function is a well-established mechanism for autosomal recessive ataxia-telangiectasia. The premature termination codon lies well upstream of the final exon and is predicted to trigger nonsense-mediated decay, removing all critical C-terminal domains (FAT, PI3K, FATC). Under the ATM VCEP v1.5 PVS1 decision tree, this meets PVS1 at Very Strong strength.¹ The variant is absent from gnomAD v4.1 and v2.1 (0 alleles observed), meeting the ATM VCEP v1.5 PM2_Supporting threshold of allele frequency ≤0.001% in the gnomAD v4 dataset.² As a truncating variant with a premature termination codon at p.Glu1995, located upstream of p.Arg3047, PM5_Supporting applies per ATM VCEP v1.5 specifications.³ No experimental functional data (PS3/BS3), case-control enrichment data (PS4), de novo observations (PS5), or co-segregation data (PP1) were identified for this specific variant in the reviewed literature. None of the three publications reviewed (PMID:27413114, PMID:30348496, PMID:30553448) mentioned NM_000051.4:c.5983G>T. Applying the ATM VCEP v1.5 final classification rules (Richards et al. 2015 combination framework): PVS1 (Very Strong) plus two Supporting pathogenic criteria (PM2_Supporting, PM5_Supporting) satisfies Rule 4 (1 Pathogenic Very Strong + ≥2 Pathogenic Supporting), resulting in a final classification of Pathogenic.⁴