A patient’s blood sample returns a negative nitroblue tetrazolium dye test. What is the most likely diagnosis?

A patient’s blood sample returns a negative nitroblue tetrazolium dye test. What is the most likely diagnosis?

• A. Severe combined immunodeficiency
• B. Job syndrome
• C. Chronic granulomatous disease
• D. X-linked agammaglobulinemia

Answer: (C)

The test hinges on the neutrophil oxidative burst. Nitroblue tetrazolium (NBT) is reduced to a blue formazan dye when reactive oxygen species are produced by the neutrophil’s NADPH oxidase during the respiratory burst. A negative result means neutrophils aren’t reducing the dye, indicating a failure to generate reactive oxygen species. This pattern is classic for chronic granulomatous disease, which stems from a defect in NADPH oxidase. Without that enzyme, neutrophils can’t make superoxide and other ROS needed to kill certain bacteria and fungi, leading to recurrent infections and granuloma formation. Other immunodeficiencies involve different problems (eg, SCID affects lymphocytes, X-linked agammaglobulinemia shows very low B cells and antibodies, Job syndrome presents with high IgE and characteristic infections) and do not specifically explain a failure of the oxidative burst measured by the NBT test.

The test hinges on the neutrophil oxidative burst. Nitroblue tetrazolium (NBT) is reduced to a blue formazan dye when reactive oxygen species are produced by the neutrophil’s NADPH oxidase during the respiratory burst. A negative result means neutrophils aren’t reducing the dye, indicating a failure to generate reactive oxygen species.

This pattern is classic for chronic granulomatous disease, which stems from a defect in NADPH oxidase. Without that enzyme, neutrophils can’t make superoxide and other ROS needed to kill certain bacteria and fungi, leading to recurrent infections and granuloma formation.

Other immunodeficiencies involve different problems (eg, SCID affects lymphocytes, X-linked agammaglobulinemia shows very low B cells and antibodies, Job syndrome presents with high IgE and characteristic infections) and do not specifically explain a failure of the oxidative burst measured by the NBT test.