NM_000212.2(ITGB3):c.1924G>T (p.Glu642Ter) in exon 12 of 15 is a nonsense variant predicted to cause a premature stop codon in biologically-relevant-exon and is predicted to lead to nonsense mediated decay in a gene in which loss-of-function is an established disease mechanism. However, RT-PCR analysis in the proband of PMID: 9845537 found that, instead, a shortened transcript was produced (in similar quantities to the normal allele) with in-frame skipping of exons 11 and 12 (reported by authors as exons 10 and 11, using alternate numbering), resulting in removal of 14% of the protein (PVS1_strong). CHO cells were transiently cotransfected with the plasmid pcDNA3-GPIIb and either WT or mutant pcDNA3-GPIIIa with this variant. To investigate the surface exposure of GPIIb-IIIa, intact cells were labeled with biotin, and the GPIIb-IIIa complexes were immunoprecipitated with anti-GPIIb (M3) or anti-GPIIIa (P37) MoAbs. No biotin-labeled products were found in cells cotransfected with normal GPIIb and mutant GPIIIa. Additionally, to examine the intracellular presence of GPIIb and/or GPIIIa as either monomers or heterodimers, total cell lysates were labeled with biotin, and GPIIb, GPIIIa, or GPIIb-IIIa complexes were immunoprecipitated. Unlike in extracts from cells coexpressing normal subunits, heterodimers failed to immunoprecipitate using a complex-specific MoAb, suggesting that the mutant ΔGPIIIa does not complex with GPIIb. Pulse-chase experiments further verified that the mutant ΔGPIIIa does not complex to GPIIb (PMID: 9845537; PS3_supporting). This variant has been detected homozygous in at least 2 probands with Glanzmann thrombasthenia (PMIDs: 14985172, 9845537; PM3). At least one patient (Patient II.1 in PMID: 14985172) with this variant displayed mucocutaneous bleeding and impaired aggregation with all agonists except ristocetin, which is highly specific for Glanzmann thrombasthenia (PP4_moderate). Additionally, αIIbβ3 surface expression was reduced to <5%, as measured by flow cytometry and Western blot. This variant is absent from gnomAD v2.1.1 (PM2_Supporting). In summary, this variant meets the criteria to be classified as Pathogenic for autosomal recessive Glanzmann Thrombasthenia based on the ACMG/AMP criteria applied, as specified by the ClinGen PD VCEP: PVS1_strong, PS3_supporting, PP4_moderate, PM3, PM2_supporitng. (VCEP specifications version 2; date of approval 12/21/21).