BTK and agammaglobulinemia: The aim of the article is to create a decision trees for Bruton’s agammaglobulinemia based on available retrospective clinical data, including the onset of clinical signs and symptoms, organ/systemic manifestation of signs and symptoms, levels of primary immunoglobulin classes (G,A,M), number of B lymphocytes, Btk expression in B lymphocytes and monocytes, type of mutation.