Outcomes of X-Linked Agammaglobulinaemia Patients.

Background: X-linked agammaglobulinaemia (XLA), caused by mutations in BTK, is characterised by low or absent peripheral CD19 + B lymphocytes and agammaglobulinaemia. The mainstay of treatment consists of immunoglobulin replacement therapy (IgRT). As this cannot fully compensate for the immune defects in XLA, patients may therefore continue to be at risk of complications.

Objectives: To describe the clinical outcomes of XLA patients in the United Kingdom and Hong Kong and evaluate current treatment strategies.

Methods: Patients with a definitive diagnosis of XLA were included in this cross-sectional and retrospective analysis of clinical health outcomes. Data pertaining to diagnosis, infection incidence, IgG trough levels and lung function were collected and analysed.

Results: 99 patients with a median age of 29.02 years (IQR 12.83-37.41) and a total follow up of 1922 patient years, were included this study. The median age at diagnosis was 3.30 years (IQR 1.04-8.38) which decreased over time (p = 0.004). 40% of the cohort had radiological evidence of bronchiectasis. Risk of bronchiectasis was not significantly associated with clinical infection incidence (p = 0.880) or IgG trough levels (p = 0.407). Two patients demonstrated novel complications, namely persistent norovirus infection, leading to haemopoietic stem cell transplantation (HSCT).

Conclusions: Despite modern therapy, most XLA patients continue to experience complications, most notably bronchiectasis, likely due to absence of IgA/M in current therapies, but lack of B lymphocytes may also lead to additional sequalae. These data strongly support the need for further research, particularly that of curative modalities including HSCT and gene therapy.