Atypical Manifestation of X-linked Agammaglobulinemia - the Importance of Genetic Testing.

X-linked agammaglobulinemia (XLA) was one of the first inborn errors of immunity to be described. It is caused by pathogenic variants in the gene for Bruton tyrosine kinase (BTK), which has important functions in B cell development and maturation. Recurrent bacterial infections in the first two years of life and hypogammaglobulinemia with absent B cells in male patients are the most common symptoms.