Serum total tryptase levels are increased in patients with active chronic urticaria

Summary Background We have demonstrated previously mast cell histamine release upon incubation with chronic urticaria (CU) sera, presumably by degranulation. Objective To explore total and mature tryptase in order to assess whether any increase in total tryptase levels is due in part to mast cell degranulation or to mast cell burden. We also wanted to explore differences between the autoimmune groups called idiopathic (serum unable to activate basophils), and to correlate total and mature tryptase levels with different urticaria features. Methods We measured total and mature tryptase serum levels in 81 CU patients, 16 atopic donors and 21 healthy control sera. We assessed autoimmunity by measuring the CD63 expression in normal basophil donors upon incubation with CU sera. Results We found significantly higher levels of total tryptase in the sera of CU patients (6.6 ±4.1 μg/L) than in sera from healthy non‐atopic subjects (4.4 ±2.8 μg/L) and from atopic subjects (4.5 ±1.7 μg/L). Mature tryptase levels were undetectable (