SERPINC1 and ataxia telangiectasia: SERPINC1 gene defects are considered the strongest inherited risk factors for VTE so that AT homozygous deficiency causes embryonic death and the combination of different SERPINC1 mutations or variants is responsible for the recently fascinating described genotype-phenotype gradient, that is, the clinical variability found among carriers of the same or different combination of SERPINC1 defects [25,26,27].