Which immunologic finding is most consistent with X-linked agammaglobulinemia?

Which immunologic finding is most consistent with X-linked agammaglobulinemia?

• A. Normal B cells
• B. Decreased T cells
• C. Decreased NK cells
• D. Decreased B cells

Answer: (D)

X-linked agammaglobulinemia is caused by a defect in B cell maturation due to BTK deficiency. Because B cells cannot progress beyond early stages, there are very few mature B cells in the peripheral blood and immunoglobulins of all classes are markedly low. T cells and NK cells develop normally, so cellular immunity remains relatively intact. The hallmark finding is a pronounced decrease in B cells, which explains the deficient humoral antibody responses and recurrent bacterial infections seen after maternal antibodies wane.

X-linked agammaglobulinemia is caused by a defect in B cell maturation due to BTK deficiency. Because B cells cannot progress beyond early stages, there are very few mature B cells in the peripheral blood and immunoglobulins of all classes are markedly low. T cells and NK cells develop normally, so cellular immunity remains relatively intact. The hallmark finding is a pronounced decrease in B cells, which explains the deficient humoral antibody responses and recurrent bacterial infections seen after maternal antibodies wane.