# Chronic Granulomatous Disease

> Chronic granulomatous disease for NEET-PG Paediatrics covers NADPH oxidase defects, catalase-positive infections, NBT and DHR tests, prophylaxis and transplant.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/chronic-granulomatous-disease
- Exam / course: NEET-PG · Subject: Paediatrics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Nelson Textbook of Pediatrics; Ghai Essential Pediatrics
- How to cite: "Chronic Granulomatous Disease", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/chronic-granulomatous-disease

## Direct answer

Chronic granulomatous disease is an inherited phagocyte disorder in which the NADPH oxidase enzyme cannot generate superoxide, so neutrophils and macrophages fail to kill catalase-positive bacteria and fungi. Patients develop recurrent deep abscesses, lymphadenitis and granulomas from early childhood. The nitroblue tetrazolium test or dihydrorhodamine flow cytometry confirms the diagnosis, and prophylactic antibiotics and antifungals reduce infections.

## What you must remember

- **Enzyme complex:** NADPH oxidase, with gp91phox encoded by CYBB in the X-linked form, which is the majority of cases.
- **Autosomal forms:** defects in the p47phox, p22phox or p67phox subunits, which are autosomal recessive.
- **Catalase-positive organisms:** Staphylococcus aureus, Serratia marcescens, Burkholderia cepacia, Nocardia and Aspergillus species are the classic pathogens.
- **Clinical pattern:** lymphadenitis, liver abscess, osteomyelitis, perianal abscess, pneumonia and granulomatous colitis.
- **Screening test:** the nitroblue tetrazolium test is negative in CGD, since neutrophils fail to reduce the dye to blue formazan.
- **Modern test:** dihydrorhodamine (DHR) flow cytometry measures the oxidative burst and can detect carriers, who show a mosaic pattern.
- **Prophylaxis:** co-trimoxazole against bacteria and Pneumocystis, itraconazole against Aspergillus, and interferon gamma used in many patients.
- **Curative option:** haematopoietic stem cell transplantation, considered for severe disease with a suitable donor.

## A pathway from suspicion to protection

Recurrent deep abscesses in a child are the trigger for testing. The steps below move from the infection pattern to a confirmed diagnosis and long-term prevention.

1. **Suspect from the infections:** recurrent abscesses, lymphadenitis or pneumonia with catalase-positive organisms in a child warrant an oxidative burst test.
2. **Test the oxidative burst:** the DHR flow cytometry test or the NBT test shows a negative or markedly reduced response in CGD.
3. **Identify the subunit:** genetic testing for CYBB or the autosomal subunit genes confirms the defect and guides carrier counselling for relatives.
4. **Prevent infection:** co-trimoxazole, itraconazole and interferon gamma are used per standard practice, and live BCG vaccine is avoided in confirmed or suspected cases.
5. **Treat abscesses early:** deep abscesses are drained and cultured, with antibiotics chosen to cover Staphylococcus aureus while results are awaited.
6. **Consider transplant:** haematopoietic stem cell transplantation is considered for severe or recurrent disease, with donor choice guided by the family and transplant team.

## Where the exam tests chronic granulomatous disease

Questions focus on the screening test, the organism list and the prophylaxis. These traps recur in NEET-PG papers.

- **Trap:** calling recurrent skin or liver abscesses in a boy routine cellulitis. — **Correct:** recurrent deep abscesses with catalase-positive organisms suggest CGD and should prompt an oxidative burst test.
- **Trap:** reading a normal neutrophil count as excluding CGD. — **Correct:** neutrophil numbers are normal in CGD, because the defect is in killing, so the NBT or DHR test is the investigation.
- **Trap:** assuming Streptococcus pyogenes is a typical CGD pathogen. — **Correct:** the classic CGD pathogens are catalase-positive, such as Staphylococcus aureus, Serratia and Aspergillus.

## Frequently asked questions

### Which test confirms chronic granulomatous disease?

The nitroblue tetrazolium test and dihydrorhodamine flow cytometry confirm chronic granulomatous disease by measuring the neutrophil oxidative burst. A negative or markedly reduced response points to a defect in the NADPH oxidase enzyme.

### Why are catalase-positive organisms important in chronic granulomatous disease?

Staphylococcus aureus, Serratia and Aspergillus are the classic pathogens in chronic granulomatous disease, and their pattern of repeated infection prompts testing for the oxidative burst defect. A child with recurrent infection by these organisms should be evaluated early.

### Which prophylaxis is used in chronic granulomatous disease?

Co-trimoxazole prophylaxis against bacterial and Pneumocystis infection and itraconazole against Aspergillus are commonly used in chronic granulomatous disease. Interferon gamma is also used in many patients to reduce serious infections.

### Is chronic granulomatous disease always X-linked?

Most cases of chronic granulomatous disease are X-linked, caused by CYBB mutations that encode gp91phox. Autosomal recessive forms also occur, due to defects in other NADPH oxidase subunits such as p47phox.