Chronic granulomatous disease: NADPH oxidase and the respiratory burst
The neutrophils are present in normal number, yet they cannot kill. Follow one oxygen molecule through the respiratory burst to see why infections persist in chronic granulomatous disease.
Explain how NADPH oxidase deficiency impairs the respiratory burst and why catalase-positive organisms cause infection in chronic granulomatous disease (CGD).
The short version
- NADPH oxidase, superoxide dismutase and myeloperoxidase turn oxygen into superoxide, then hydrogen peroxide, then hypochlorous acid (bleach).
- Chronic granulomatous disease is a fault in step one, the NADPH oxidase: little hydrogen peroxide, no bleach, and microbes persist.
- Catalase-positive organisms (Staphylococcus aureus, Aspergillus, Burkholderia cepacia, Serratia marcescens, Nocardia) cause the infections.
- Infection is walled off into granulomas, most often in the gut and urinary tract, and most patients are diagnosed before the age of five.
- The nitroblue tetrazolium dye stays yellow and the dihydrorhodamine flow cytometry test is flat.
Chronic granulomatous disease: neutrophils that are present but cannot kill
A three-year-old boy has a swollen, abscessed lymph node in his neck, and the culture grows Serratia marcescens. His immunoglobulins are normal, and so is his neutrophil count.
The neutrophils are there. So why can they not kill? The answer is chronic granulomatous disease (CGD): an inherited fault in the oxygen-dependent killing step that phagocytes rely on.[1][7]
The respiratory burst: follow one oxygen molecule
A neutrophil swallows a microbe into a phagosome. Killing then needs an oxygen-dependent step called the respiratory burst.[1][7]
- Step one: NADPH oxidaseA complex on the phagosome membrane passes electrons from NADPH to oxygen and makes superoxide.[1][2]
- Step two: superoxide dismutaseIt turns superoxide into hydrogen peroxide.[1][2]
- Step three: myeloperoxidaseIt combines hydrogen peroxide with chloride to make hypochlorous acid, which is bleach.[1][3]
One NADPH and two oxygen molecules give two superoxide ions.
The chain, in order: oxygen → superoxide → hydrogen peroxide → hypochlorous acid. Every later step depends on the one before it.
What goes wrong in chronic granulomatous disease
CGD is a fault in step one. The oxidase has several subunits. A fault in gp91phox is X-linked, so it mainly affects boys; faults in the other subunits are autosomal recessive.[1][2]
Little or no superoxide means little hydrogen peroxide, and no bleach. Microbes are not killed properly, so they persist.[1][2][7]
Why catalase-positive organisms cause the infections
Catalase breaks down hydrogen peroxide. Catalase-positive microbes destroy even the little hydrogen peroxide the phagocyte still makes, so they are the ones that cause the trouble.[2][5]
- Staphylococcus aureus
- Aspergillus
- Burkholderia cepacia
- Serratia marcescens
- Nocardia
Staphylococcus aureus and Aspergillus are the two most frequent.[1][2]
Sites, granulomas and age at diagnosis
The infections arise in the lungs, lymph nodes, skin and liver.[1][4]
The persistent infection is walled off into granulomas, most often in the gut and urinary tract, which gives the disease its name.[4][7] Most patients are diagnosed before the age of five.[2]
Diagnosing CGD: the nitroblue tetrazolium and dihydrorhodamine tests
The old test stimulates neutrophils in the presence of the yellow dye nitroblue tetrazolium (NBT). Normal cells reduce it to a dark blue precipitate. In CGD, they stay yellow.[4]
Today's standard is the dihydrorhodamine (DHR) flow cytometry test: normal neutrophils oxidise the dye and fluoresce, and CGD neutrophils do not. Its dye is oxidised by hydrogen peroxide from the same chain, so it reads out the burst.[1][4]
| Test | Normal neutrophils | CGD neutrophils |
|---|---|---|
| Nitroblue tetrazolium (NBT) | Reduce the dye to a dark blue precipitate | Stay yellow |
| Dihydrorhodamine (DHR) flow cytometry | Oxidise the dye and fluoresce | Do not fluoresce |
Treatment, and back to the boy
Treatment is lifelong trimethoprim-sulfamethoxazole and itraconazole, often interferon gamma, and a stem-cell transplant can cure.[1][2][5]
Back to the boy with the neck abscess. A normal neutrophil follows the chain: oxygen, superoxide, hydrogen peroxide, bleach. His follows it only as far as oxygen. His Serratia carries catalase and his oxidase makes little or no superoxide, so the abscess stays.
Practice question
Original · USMLE styleA 7-year-old boy is admitted with a liver abscess, and the aspirate grows Staphylococcus aureus. At the age of 4 years he had Aspergillus pneumonia. His serum immunoglobulin levels and neutrophil count are normal. Neutrophils stimulated in the laboratory in the presence of nitroblue tetrazolium remain yellow.
Common questions
What causes chronic granulomatous disease?
A fault in the NADPH oxidase, step one of the respiratory burst. Without it there is little or no superoxide, little hydrogen peroxide and no bleach, so microbes are not killed properly and persist.
Why do catalase-positive organisms cause infections in CGD?
Catalase breaks down hydrogen peroxide. Catalase-positive microbes destroy even the little hydrogen peroxide the phagocyte still makes, so they are the ones that cause the trouble.
Is chronic granulomatous disease X-linked?
A fault in gp91phox is X-linked, so it mainly affects boys. Faults in the other subunits of the oxidase are autosomal recessive.
How is chronic granulomatous disease diagnosed?
The old test is nitroblue tetrazolium, which stays yellow in CGD. Today's standard is the dihydrorhodamine flow cytometry test, in which CGD neutrophils do not fluoresce.
Transcript
Read the full narration, by chapter612 words
0:00The case: normal neutrophils that cannot kill
A 3-year-old boy has a swollen, abscessed lymph node in his neck, and the culture grows Serratia marcescens. His immunoglobulins are normal, and so is his neutrophil count. The neutrophils are there. So why can they not kill? Today: explain how a missing NADPH oxidase wrecks the respiratory burst, and why catalase-positive organisms cause the infections.
0:24The respiratory burst: follow one oxygen molecule (superoxide, hydrogen peroxide, bleach)
A neutrophil swallows a microbe into a phagosome. Killing then needs an oxygen-dependent step called the respiratory burst. Follow one oxygen molecule. Step one: NADPH oxidase, a complex on the phagosome membrane, passes electrons from NADPH to oxygen and makes superoxide. The bookkeeping: one NADPH and two oxygen molecules give two superoxide ions. Step two: superoxide dismutase turns superoxide into hydrogen peroxide. Step three: myeloperoxidase combines hydrogen peroxide with chloride to make hypochlorous acid, which is bleach. Chronic granulomatous disease is a fault in
1:09Chronic granulomatous disease: a fault in step one
step one. The oxidase has several subunits. A fault in gp91phox is X-linked, so it affects boys; faults in the other subunits are autosomal recessive. No superoxide means little hydrogen peroxide, and no bleach. Microbes are not killed properly, so they persist.
1:33Catalase-positive organisms: the usual culprits
Catalase breaks down hydrogen peroxide. Catalase-positive microbes destroy even the little hydrogen peroxide the phagocyte still makes, so they are the ones that cause the trouble. The usual culprits: Staphylococcus aureus, Aspergillus, Burkholderia cepacia, Serratia marcescens and Nocardia. Staphylococcus aureus and Aspergillus are the two most frequent.
1:59Sites, granulomas and age at diagnosis
They infect the lungs, lymph nodes, skin and liver. The persistent infection is walled off into granulomas, most often in the gut and urinary tract, which gives the disease its name. Most patients are diagnosed before the age of five. The old test: neutrophils are stimulated in
2:16The tests: nitroblue tetrazolium and dihydrorhodamine
the presence of the yellow dye nitroblue tetrazolium. Normal cells reduce it to a dark blue precipitate. In CGD, they stay yellow. Today's standard is the dihydrorhodamine flow cytometry test: normal neutrophils oxidise the dye and fluoresce, and CGD neutrophils do not. Its dye is oxidised by hydrogen peroxide from the same chain, so it reads out the burst.
2:45Treatment
Treatment: lifelong trimethoprim-sulfamethoxazole and itraconazole, often interferon gamma, and a stem-cell transplant can cure. Back to our boy.
2:56Back to our boy
A normal neutrophil follows the chain: oxygen, superoxide, hydrogen peroxide, bleach. His follows it only as far as oxygen. His Serratia carries catalase and his oxidase makes no superoxide, so the abscess stays.
3:13Practice question
Your turn. A 7-year-old boy is admitted with a liver abscess, and the aspirate grows Staphylococcus aureus. At the age of four he had Aspergillus pneumonia. His immunoglobulins and neutrophil count are normal. Neutrophils stimulated in the lab in the presence of nitroblue tetrazolium remain yellow. Which of the following is the most likely cause? A, NADPH oxidase deficiency in phagocytes. B, myeloperoxidase deficiency in neutrophils. C, CD 18 deficiency on leukocytes. D, Bruton tyrosine kinase deficiency in B cells. E, terminal complement component deficiency. Pause here and decide.
4:02Why B, C, D and E are out
B is out: myeloperoxidase works after superoxide and hydrogen peroxide have formed, so these neutrophils would still turn the dye blue. C is out: CD 18 loss gives a high neutrophil count, delayed cord separation and pus-free infections. D is out: lack of BTK lowers the immunoglobulins, and his are normal. E is out: terminal complement loss gives recurrent Neisseria infection. So the answer is A.
4:32The answer: NADPH oxidase deficiency
Neutrophils that cannot reduce the dye cannot make superoxide, and Staphylococcus aureus and Aspergillus are the catalase-positive organisms that follow. Three things to keep.
4:45Recap and next lesson
One: NADPH oxidase makes superoxide, then hydrogen peroxide, then bleach; CGD breaks step one. Two: catalase-positive organisms, Staphylococcus, Aspergillus, Burkholderia, Serratia and Nocardia, cause the infections. Three: the dye stays yellow and the dihydrorhodamine test is flat. Next, leukocyte adhesion deficiency, where neutrophils cannot leave the blood.
Sources
Numbers in the text, e.g. [1], point here- Staudacher O, von Bernuth H. Chronic granulomatous disease. Front Pediatr 2024. europepmc.org/article/PMC/PMC11239527
- Arnold DE, Heimall JR. A review of chronic granulomatous disease. Adv Ther 2017. europepmc.org/article/PMC/PMC5709447
- Chronic granulomatous disease: lessons in cell biology. Europe PMC. europepmc.org/article/PMC/PMC12658887
- Considerations in the diagnosis of chronic granulomatous disease. europepmc.org/article/PMC/PMC5946934
- A fatal case of chronic granulomatous disease. europepmc.org/article/PMC/PMC10335941
- Geographic variability and pathogen-specific considerations in chronic granulomatous disease. europepmc.org/article/PMC/PMC7383027
- OpenStax Microbiology, 19.4 Immunodeficiency. openstax.org/books/microbiology/pages/19-4-immunodeficiency
- Leukocyte adhesion deficiency type 1 (CD18): europepmc.org/article/PMC/PMC8998723 · europepmc.org/article/PMC/PMC10619948
- X-linked agammaglobulinaemia (BTK): europepmc.org/article/PMC/PMC8269404
- Terminal complement deficiency: MSD Manual Professional, Overview of immunodeficiency disorders. msdmanuals.com/professional/immunology-allergic-disorders/immunodeficiency-disorders/overview-of-immunodeficiency-disorders · europepmc.org/article/PMC/PMC11714877
The catalase-positive pattern is the standard exam convention; the literature notes it is a simplification.
The practice question is original and its patient is synthetic. Every fact is checked against the sources above in independent accuracy reviews. Always follow your local guidelines and your own laboratory’s ranges.
Image credits. Illustrations: Servier Medical Art (smart.servier.com), CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), adapted (recoloured, outlined): neutrophil granulocyte, Aspergillus fumigatus. Phagocytosis icon by Servier via Bioicons (bioicons.com), CC BY 3.0 (https://creativecommons.org/licenses/by/3.0/), adapted (recoloured, outlined). Icons: Health Icons (healthicons.org), CC0: child, lymph node, lungs, liver, medicine container. The respiratory-burst chain, oxidase complex, catalase scissors, test tubes, DHR histogram (schematic) and all handwriting are drawn in code (original). No AI-generated teaching images.
Corrections. None so far. Spotted an error? Email info@medservatory.com with the lesson code MS-S1-IMM-014.
For exam study only, not medical advice. Read the medical disclaimer.
In this series
Playlist on YouTube- EP 01MHC I vs MHC II: how antigen presentation works5:03
- EP 02T-cell activation: the two-signal model4:58
- EP 03Th1, Th2, Th17 and Treg: helper T-cell subsets5:13
- EP 04Antibody isotypes and class switching5:13
- EP 05Central vs peripheral tolerance: how lymphocytes learn self-tolerance5:26
- EP 06Complement system explained: three pathways, one ending5:24
- EP 07Complement deficiencies: C1q, C3, C5–C9 and C1 inhibitor5:15
- EP 08Hypersensitivity types I to IV: the four effectors5:20
- EP 09B-cell vs T-cell immunodeficiency: predict the infections5:24
- EP 10Hyper IgM syndrome: CD40 ligand and class switching5:19
- EP 11Chronic granulomatous disease: NADPH oxidase and the respiratory burst5:20
- EP 12Leukocyte adhesion deficiency: CD18 and neutrophil extravasation5:01
- EP 13Transplant rejection explained: hyperacute, acute, chronic and GVHD5:51
- EP 14Vaccine types explained: live, inactivated, conjugate and mRNA5:41