X‐linked agammaglobulinemia (XLA) is a congenital immunodeficiency disorder that results from impaired B‐cell differentiation due to Bruton tyrosine kinase (BTK) mutations, leading to a decrease in mature B‐cells, impaired antibody production, and hypogammaglobulinemia [1, 2, 3]. The gene discussed is BTK; the disease is agammaglobulinemia.