X-linked agammaglobulinemia (XLA) is a clinically variable form of isolated agammaglobulinemia, an inherited immunodeficiency disorder (see this term), and is characterized in affected males by recurrent bacterial infections during infancy. The disease is Orphanet rare-disease nomenclature term Orphanet_47 (X-linked agammaglobulinemia). Also known as: BTK-deficiency, Bruton type agammaglobulinemia.