D2.326 - The frequency of hereditary α-tryptasemia (HαT) in patenits with insect venom anaphylaxis and in patients with mastocytosis – preliminary results

Mastocytosis is a hematopoietic neoplasm characterized by expansion  clonal mast cells in various organs and severe anaphylactic reactions. Recently, hereditary α-tryptasemia (HαT) has been described as a common genetic trait with increased copy numbers of the α-tryptase encoding gene, TPSAB1, and associated with a risk of severe anaphylaxis and the influence on the occurrence of mast cell activation symptoms in patients mastocytosis.

Objective: We evaluated the prevalence of HαT in patients with mastocytosis and patients with venom allergy and assessed the pathophysiologic association with HαT.

Clinical data, laboratory data, KIT mutations,TPSAB1 duplication (assessed by droplet digital PCR), and HAT prevalence were recorded for patients with mastocytosis and venom allergy.

We included 125 patients (67 with mastocytosis and 58 with IVA). Anaphylaxis was reported 74,6% of patients with mastocytosis, including in 12 patients with HαT. The assessement of anaphylaxis triggers in mastocytosis group was as follows: venom allergy in 35 cases (70% anaphylactic reactions), drugs in 8 cases (16%) and unknown in 5 cases (10%). All anaphylactic reactions of patients including to this study were severe anaphylactic reactions. The prevalence of HαT in all patients was 16%; in mastocytosis group was 20,9%, and in venom allergy patients 10,3%; which is higher than in the general population (5%). In the subgroup of patients with mastocytosis those with HαT 85,7% presented the history of anaphylaxis. In mastocytosis with HαT the most common triggers were as follows: IVA in 8 patients, drugs in 3 and unknown in 2 cases which were similar to patients without HαT.

We confirmed the prevalance about 20,9% in mastocytosis patients with the 74,6% of incidence of anaphylaxis and about 10,3% in patients with insect venom anaphylaxis with confirmed allergy do specific venom. HαT seems to be promising predictive factor of anaphylaxis in mastocytosis.