TPSAB1 duplications occur at 16p13.3 and are linked to an expanded promoter associated with α^DUP-tryptase overexpression. (A) Location and orientation of the 15-kb tandem duplication of TPSAB1. (B) Alignment of α^DUP-, α^WT-, and β-tryptases with unique 5′ variants and size of promoter repeat regions indicated; (C) repeat motif within promoter regions. Relative total α- to β-tryptase gene expression (D) and α^DUP-tryptase relative to α^WT-tryptase gene expression (E) in ex vivo basophils and cultured primary mast cells. ∗P < .05; ∗∗P < .005.