Diagnosis, Characteristics, and Outcome of Selective Anti-polysaccharide Antibody Deficiencies In A Retrospective Cohort of 55 Adult Patients.

Selective anti-polysaccharide antibody deficiency (SPAD) predisposes to encapsulated bacterial infections. The diagnosis is challenging, and literature reports are scarce in adult patients, we therefore aim to describe the demographics, infectious complications, therapeutic strategies, and outcome of adult patients. We conducted a multicenter observational study involving 55 adult patients with SPAD. The median [interquartile range, IQR] age was 45 [36-60] years at diagnosis of SPAD, and 75% of patients were female. Twenty-one patients (38%) had a history of allergic and/or inflammatory disease, mainly asthma (n = 12), and rheumatic diseases (n = 6). Twelve patients (22%) were diagnosed after a single severe infection and 43 (78%) in a context of recurrent benign and/or severe infections. In the latter, the median time from first infections to diagnosis was 74.5 [33-167] months. Diagnostic delay was significantly higher in patients presenting with bronchiectasis than in those without (122 months [33-219.5] vs 24 months [14.5-74.5], p = 0.0042). In 22 patients (40%) receiving immunoglobulin replacement therapy (IgRT), the mean (min-max) frequency of antibiotic courses decreased from 7.9 (2-18) to 0.7 (0-2) courses per year (p < 0.001) with a median follow-up period of 46 [27-73] months. Patients diagnosed after a single severe infection did not have any relapse during a median follow-up of 85 [80.5-104.5] months after diagnosis. Adult patients with SPAD have allergic or inflammatory disorders which could contribute to the diagnostic delay. IgRT is effective in preventing recurrent infections. Further studies are warranted to confirm if SPAD should be considered after a first unexplained severe bacterial infection.