What are the rheumatologic manifestations of XLA?
XLA is a rare disorder characterized by absent or near-absent levels of serum IgG, IgM, and IgA and by abnormal in vivo B-cell functional tests due to a defect within the Bruton’s tyrosine kinase (BTK) gene, resulting in abnormal function of this signal transduction protein, which is normally present within B cells at all stages of development. This results in the characteristic cellular abnormalities, such as failure of maturation of the B-cell line and absence of B cells. Arthritis occurs in approximately 20% of patients, with half of these cases due to infection with the typical pyogenic bacteria. Furthermore, patients appear vulnerable to infections with enterovirus and Mycoplasma .
There are cases of arthritis in XLA in which an infectious agent cannot be detected despite rigorous evaluation. Our clinical experience with patients with agammaglobulinemia or hypogammaglobulinemia and arthritis is that they much more commonly have aseptic arthritis (either inflammatory or degenerative in nature) or arthralgias without arthritis. However, atypical organisms such as Ureaplasma urealyticum and Mycoplasma species organisms have been reported in patients with PID syndromes who present with a more “subacute” clinical picture (pain and persistent joint swelling but no diminished range of motion, joint is not hot or red). In these cases, a trial of doxycycline or a macrolide has been suggested, though the duration of therapy is unclear
