These deficiencies include X-linked agammaglobulinemia (XLA), also known as Bruton's tyrosine kinase (BTK) deficiency; certain types of autosomal-dominant immunodeficiencies (such as Hoffman syndrome, PU1 deficiency, and E47 transcription factor deficiency), and several autosomal-recessive immunodeficiencies. The gene discussed is SPI1; the disease is Bruton-type agammaglobulinemia.