Hereditary Alpha-Tryptasemia (HαT) as a Risk Modifier for Severe Anaphylaxis.

Hereditary alpha-tryptasemia (HαT) is a common autosomal dominant genetic trait that results from increased copy numbers of the TPSAB1 gene encoding α-tryptase. Studies have shown that increased relative α-tryptase expression can modify mast-cell-mediated reactions and contribute to increased severity of anaphylaxis. HαT is an independent risk modifier for reaction severity in patients with Hymenoptera venom allergy and systemic mastocytosis. Additionally, there is emerging evidence that HαT and α-tryptase expression more generally are also associated with increased risk of severe reactions to other allergens. Tryptase genotyping may be a promising biomarker for risk stratification of IgE-mediated allergic reaction severity in the future.