Diagnostic measures in patients with severe insect sting reactions and elevated baseline serum tryptase levels.

Mastocytosis or an elevated basal serum tryptase (bST) level are known risk factors for patients with insect venom allergy. We report on 3 patients with a history of severe anaphylactic insect sting reactions who underwent a detailed workup for insect venom allergy before starting venom immunotherapy. In addition to insect venom sensitization, an elevated concentration of bST (15.5, 20.8, and 23.2 µg/L) was found in all cases. There was no evidence of mastocytosis in the skin (MIS). Further testing revealed hereditary α-hypertryptasemia (HαT) in 2 patients and a D816V mutation by liquid biopsy in 1 patient, which is a minor diagnostic criterion for indolent systemic mastocytosis. Even without iliac crest puncture, causes of elevated bST can be narrowed down with minimally invasive diagnostic measures. As this has practical implications, patients with elevated bST should always undergo further work-up to determine the cause of this abnormal finding.