X-linked agammaglobulinemia (XLA) is an inherited disorder that occurs only in boys, in which they have extremely low levels of certain antibodies needed to fight infection. As a result, they have frequent infections, most often of the lungs, sinuses, and bones.

X-linked agammaglobulinemia usually first appears in infant boys 6 to 9 months old. Boys with agammaglobulinemia need regular treatment with antibiotics or immunoglobulin (IG) to help prevent serious infection.