Disease spectrum in patients with elevated serum tryptase levels

Elevated serum tryptase levels can be a sign of mastocytosis, which is a rare disease associated with systemic and/or skin manifestations.

To investigate patients with elevated tryptase levels in regard to their underlying diseases, and to determine whether increased tryptase can be used as a diagnostic marker for underlying mastocytosis.

In a retrospective study the data of 96 patients with serum tryptase levels higher than 15 μg/L were systematically analysed. In 48 patients control investigations for baseline tryptase were performed.

Fifty-three of the 96 patients had tryptase levels ≥20 μg/L. A mere 16% of the 96 patients suffered from mastocytosis and had the highest tryptase levels (P < 0.001). The remaining patients had anaphylaxis (36%), urticaria and angioedema (26%), local reactions to insect bites (4%), drug reactions (3%), or miscellaneous diagnoses (15%). Only 16 of these had acute symptoms at tryptase investigation. In all, 48 patients had a follow up; in 7/48 patients with acute symptoms normal tryptase levels were seen at control investigations, but 41/48 (85%) patients showed continuously elevated tryptase levels >15 μg/L and in 30 patients (62%) even values >20 μg/L; 11 of these patients had anaphylaxis, five urticaria, five other diagnoses and nine patients mastocytosis.

More than 50% of patients with non-mastocytosis such as urticaria and angioedema, drug or anaphylactic reactions repeatedly had tryptase levels higher than 20 μg/L. Since baseline tryptase >20 μg/L is a minor criterion for mastocytosis, these patients should be inspected for skin lesions of mastocytosis and receive a diagnostic body work-up for systemic mastocytosis including a bone marrow biopsy.