Clinical and Molecular Characteristics of X-Linked Agammaglobulinemia Patients 55 Years or Older.

Abstract

X-linked agammaglobulinemia (XLA), caused by mutations in the Bruton tyrosine kinase (BTK) gene, leads to defective B-cell development and low or absent serum immunoglobulins. Advances in diagnosis and treatment have improved outcomes, allowing some patients to live beyond their sixth decade. To describe the clinical, genetic, treatment, and functional status of XLA patients aged 55 years or older. Immunologists provided anonymized, physician-reported clinical and molecular details of XLA patients aged 55 years or older. Patients were categorized as having missense mutations (BTK missense) or non-missense mutations (BTK non-missense). Fifty-seven patients were submitted. Forty-eight were considered for final analysis, including 43 with molecularly confirmed XLA and 5 with a strong clinical history. Persistent respiratory infections were common: 64.6% (upper respiratory tract) and 83.3% (lower respiratory tract). Chronic lung disease (72.9%) and gastrointestinal/hepatic disorders (47.9%) were among the most prevalent complications. Most living patients (80.5%) reported good functional status (Karnofsky scores > 80). Missense variants accounted for 62.8% (n = 27), non-missense variants for 37.2% (n = 16); 5 patients lacked classifiable mutation details. Among 34 patients with BTK expression data, 70.6% had detectable BTK protein, significantly more common in the missense group (83.3% vs 30%; P = .005). The non-missense group had higher mortality, more infections, greater antibiotic use, worse pulmonary function, and lower functional status. Chronic respiratory complications are common in older XLA patients, although most maintain good functional status. Genetic testing aids prognostication; BTK missense mutations are linked to better outcomes. Further research is needed to address the unique challenges of aging in XLA.