Hereditary α tryptasemia predisposes to hymenoptera venom allergy and severe mediator symptoms in patients with mastocytosis. (A) Frequency of allergy in patients with or without α-tryptase encoding TPSAB1 gain. Hymenoptera venom allergy is depicted in red; other types of allergy are in blue. (B-C) Frequency of any mediator-related symptoms (B) and cardiovascular mediator-related symptoms (C) in patients with or without α-tryptase encoding TPSAB1 gain. Mild symptoms (grade 1-2) are depicted in blue; severe symptoms (grade 3-4) are in red. (D) Severity grade of mediator-related symptoms in patients without α-tryptase encoding TPSAB1 gain (green), 2α:3β (blue squares), 3α:anyβ (blue triangles), or ≥4α:anyβ (blue hexagons) tryptase genotype. Horizontal red lines indicate the median severity grade. (E-F) Frequency of hymenoptera venom allergy (E) and severe cardiovascular mediator-related symptoms (F) in patients with or without α-tryptase encoding TPSAB1 gain of an independent validation cohort.