A patient with a history of recurrent bacterial infections, particularly encapsulated bacteria, is found to have absent CD19+ B cells in peripheral blood. Which of the following primary immunodeficiency disorders is most likely?

✓ Correct Answer: Option B

X-linked agammaglobulinemia (Bruton's) is characterized by a defect in B cell development due to a mutation in Bruton's tyrosine kinase (BTK). This leads to a lack of mature B cells (CD19+) and, consequently, very low immunoglobulin levels, resulting in recurrent infections.