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Background: The main treatment of common variable immunodeficiency (CVID) is to maintain immunoglobulin G (IgG) levels within the target range. However, trough IgG levels differ among patients with similar body mass index (BMI) and those receiving the same dose of immunoglobulin replacement therapy (IGRT). A crucial factor that underlies these differences is the presence of extensive bronchiectasis, which is associated with the immunoglobulin salvage pathway. Objective: We compared trough IgG levels in patients with CVID and with and in those without bronchiectasis who had received the same dose of IGRT for 2 years to determine the association of IgG level with infection frequency. Method: This retrospective cohort study included 61 patients with CVID, of whom 21 had bronchiectasis. We reviewed the electronic records for demographic variables, baseline immunoglobulin levels, mean trough IgG levels over 2 years, efficacy levels (trough IgG level - baseline IgG level), the time interval from treatment initiation to achieving the target trough IgG level (700 mg/dL), and the number of infections. Results: The median age of the patients was 39 years (IQR, 27-51), and 29 were women (47.5%). There were no significant differences between the groups in terms of age, age at diagnosis, delay in diagnosis, sex, BMI, IGRT type (subcutaneous or intravenous), and baseline immunoglobulin levels. Trough IgG and efficacy levels were lower (P < 0.001 and P = 0.016, respectively), the time required to achieve the target IgG level was longer in patients with bronchiectasis than in those without bronchiectasis, and this time interval was significantly associated with the infection frequency. Trough IgG and albumin levels were correlated (p = 0.007), with minor differences between the groups (p = 0.04). Conclusion: Bronchiectasis was significantly associated with a longer time to achieve the target IgG levels. These long-term differences between the patients with and those without bronchiectasis have significant clinical implications.

Background: Autoimmune diseases can occur at any time in patients with common variable immunodeficiency (CVID). However, the relationship between low immunoglobulin E (IgE) levels and autoimmune diseases in patients with CVID remains poorly understood. Objective: We aimed to determine the relationship between autoimmunity and low IgE in patients with CVID. Methods: This retrospective cohort study was conducted by using data that had been collected from 62 adult patients with CVID between April 2012 and December 2021. Serum basal IgE levels were compared between patients with and patients without autoimmune disease. Results: Overall, 23 of the 62 patients with CVID (37.1%) had at least one autoimmune disease (CVID-O). Autoimmune cytopenias, mainly immune thrombocytopenic purpura, were observed in half of all the patients. Other autoimmune diseases present among the patients included rheumatological diseases, inflammatory bowel diseases, lymphoma, granulomatous lymphocytic interstitial lung disease, autoimmune hepatitis, alopecia, and multiple sclerosis. Serum IgE levels were measured at the time of diagnosis; IgE was undetectable (<2.5 IU/mL) in 82.6% of the patients with CVID-O (n = 19). The median (interquartile range) serum IgE value in the patients with CVID-O was 2 IU/mL (1-16 IU/mL), which was significantly lower than the median serum IgE value in patients with CVID and without autoimmune disease (p < 0.001). Low IgE levels in patients with CVID-O were an independent risk factor for the development of autoimmune disease in patients with CVID (odds ratio 3.081 [95% confidence interval, 1.222-7.771]; p = 0.017). Conclusion: Low serum IgE levels were associated with the development of autoimmune disease in patients with CVID. The monitoring of serum IgE levels in patients with CVID may be useful in the early diagnosis and treatment of autoimmune diseases.