A nurse is providing care for a 17-year-old boy who has experienced recurrent sinus and chest infections throughout his life and presently has enlarged tonsils and lymph nodes. Blood work indicated normal levels of B cells and free immunoglobulins but a lack of differentiation into normal plasma cells. The boy is currently receiving intravenous immunoglobulin (IVIG) therapy. What is the boy’s most likely diagnosis?
A. X-linked hypogammaglobulinemia
B. Transient hypoglobulinemia
C. Common variable immunodeficiency
D. IgG subclass deficiency