Table 1.

Conditions associated with an elevated basal serum tryptase level

Condition	Typical range of serum tryptase in ng/ml*	Increased risk for MCAS
Hereditary alpha tryptasemia	15–50**	+/-***
Cutaneous mastocytosis	5–15	+
Indolent systemic mastocytosis	15–200	++
Smoldering systemic mastocytosis	200–1000	+
Advanced systemic mastocytosis****	100–1000	+
Myelodysplastic syndromes	10–50	-
Myeloproliferative neoplasms	10–100	-
Chronic eosinophilic leukemia	10–50	-
Myeloid neoplasms with PDGFR mutation	10–50	-
Chronic myeloid leukemia	10–50	-
Acute myeloid leukemia (AML)	10–1000	-
Core binding factor (CBF) AML	10–1000	-
Non-CBF AML	10–200	-
Chronic helminth infection	10–20	-***
Chronic renal failure	10–30	-

Table 1 was reproduced in slightly modified form from Valent et al., Int Arch Allergy Immunol [48] with the Editor´s permission

Score: ++ substantial risk to develop MCAS events one or more times per year despite therapy with anti-mediator-type drugs, + increased risk to develop MCAS events one or more times over several years, +/- MCAS events have been reported in individual patients, but the precise incidence is not clear, - no increased risk to develop MCAS events compared to the general population (± allergic individuals).

*Range of basal serum tryptase concentration where a majority of cases are found; **In patients with hereditary alpha tryptasemia, the serum tryptase level increases 7–15 ng/ml with each additional TPSAB1 gene copy; in those with multiple copies, tryptase levels can increase up to 100 ng/ml; ***In these conditions, the incidence of severe anaphylaxis (MCAS) is not known although some reports suggest an increased risk; ****Advanced systemic mastocytosis includes patients with aggressive systemic mastocytosis and mast cell leukemia. In these patients, the basal tryptase level may increase to > 500 or even > 1000 ng/ml. Abbreviations: MCAS, mast cell activation syndrome