X-linked agammaglobulinemia

X-linked agammaglobulinemia, abbreviated XLA, is a rare genetic disorder that impairs the body's ability to fight infection because the body cannot make mature B cells, which produce antibodies. First described in 1952, it is a primary immunodeficiency caused by a mutation on the X chromosome, so it is much more common in males. Affected people lack the enzyme Bruton's tyrosine kinase, which mediates the step from pre-B cell to immature B cell, and so have no gamma globulins or antibodies in the blood. They typically present in early childhood with recurrent infections, especially from encapsulated bacteria, and serious or fatal infections are common. The incidence is about 1 in 200,000 live births, with no ethnic predisposition. Treatment is infusion of human immunoglobulin, which cannot restore B cells but reduces the number and severity of infections.