B lymphocyte subsets and outcomes in patients with an initial diagnosis of transient hypogammaglobulinemia of infancy

Purpose Transient hypogammaglobulinemia of infancy ( THI ) is a common immunodeficiency, but definitive diagnosis can only be made retrospectively. While the pathogenesis is still unknown, abnormalities have been reported in the B cell compartment. In this study, we analysed the B cell subsets of patients with an initial THI diagnosis (n = 20) and compared them with those of healthy age‐matched Turkish children (n = 72). Methods Flow cytometric analyses of the B subsets were performed by staining with anti‐ CD 27‐ PE , anti‐ CD 19‐Per CP , anti‐IgD‐ FITC and anti‐IgM‐ APC antibodies. Results During a median follow‐up of 6.6 years, 13 patients whose IgG levels had normalized before they reached four years of age were diagnosed with definitive THI . The memory subsets of these patients were lower but not statistically different from the healthy controls ( HC ). The remaining seven patients had prolonged hypogammaglobulinemia after the age of four and had significantly lower memory B cell subsets compared to the HC . On follow‐up, these patients had not experienced recurrent infections or autoimmunity. Re‐evaluation of patients’ B cell subsets six years later showed that the memory B cell ratios had increased to levels comparable to HC , despite the patients still having mildly low IgG levels. Conclusion Patients with prolonged hypogammaglobulinemia had lower levels of memory B cells despite having a similar clinical course to patients who had been diagnosed with definitive THI . This subgroup of putative THI patients poses a diagnostic and classification dilemma. Our results suggested that these patients’ memory B cells and IgG levels may recover over time.