BTK and isolated agammaglobulinemia: Analysis of protein profiles in patients with other IEIs showed that levels of p91-phox, Wiskott-Aldrich syndrome protein (WASP), and Bruton’s tyrosine kinase (BTK) in samples from patients with p91-phox deficiency, Wiskott-Aldrich syndrome (WAS), and X-linked agammaglobulinemia (XLA), respectively, were markedly lower than those in control samples (Fig. 4E, H, and I).