Chronic granulomatous disease (CGD) is a rare inherited immune disorder where certain white blood cells lose their ability to kill bacteria and fungi. It affects roughly 1 in 200,000 to 250,000 people, and symptoms typically appear in infancy, with most children diagnosed between ages 2.5 and 3. The core problem is a broken enzyme system inside immune cells, which leaves the body unable to mount a normal defense against specific types of infections.
How CGD Affects the Immune System
Your immune system relies on specialized cells called phagocytes, especially neutrophils, to engulf and destroy invading microorganisms. In a healthy person, when a neutrophil encounters bacteria or fungi, it undergoes a “respiratory burst,” a rapid chemical reaction that generates toxic molecules made from oxygen. These molecules, collectively called reactive oxygen species, are what actually kill the engulfed microbe.
The enzyme responsible for this burst is called NADPH oxidase. It’s a multi-part complex: some pieces sit in the cell membrane, others float in the cell’s interior, and they snap together only when the neutrophil detects a threat. Once assembled, the enzyme strips electrons from a fuel molecule inside the cell and transfers them to oxygen, producing superoxide. Superoxide and its chemical derivatives are highly toxic to bacteria.
In CGD, one of the components of this enzyme complex is missing or defective. The neutrophil can still swallow a microorganism, but it can’t generate the chemical weapons to kill it. The microbe survives inside the immune cell, leading to chronic, hard-to-treat infections. Over time, the immune system’s frustrated attempts to contain these infections produce clumps of inflamed tissue called granulomas, which give the disease its name. These granulomas most commonly form in the lungs, intestines, and urinary tract.
Genetic Causes and Inheritance
CGD results from mutations in any of six genes, each encoding a different piece of the NADPH oxidase complex. The most common form, accounting for about 66% of all cases, is caused by mutations in the CYBB gene on the X chromosome. Because of X-linked inheritance, this form almost exclusively affects boys. Mothers who carry one mutated copy of CYBB typically don’t get sick but have a 50% chance of passing the condition to each son.
The remaining cases are autosomal recessive, meaning a child must inherit a defective copy of the gene from both parents. The NCF1 gene accounts for roughly 20% of CGD cases, while mutations in CYBA and NCF2 each cause about 7%. A few other genes are responsible for very rare forms. Because autosomal recessive CGD requires two faulty copies, it affects boys and girls equally.
The genetic subtype matters clinically. Boys with X-linked CGD tend to be diagnosed earlier, experience more frequent and severe complications (including liver abscesses, obstructions of the stomach or urinary tract, and infected lymph nodes), and historically have faced higher mortality at younger ages compared to those with autosomal recessive forms.
Which Infections Are Most Dangerous
People with CGD are not vulnerable to every pathogen. The key vulnerability is to “catalase-positive” organisms. Many harmless bacteria produce small amounts of hydrogen peroxide as a byproduct of their metabolism, and a healthy immune system can actually use that peroxide as raw material to help kill the bacteria. Catalase-positive organisms, however, break down the peroxide they produce, effectively disarming this backup killing mechanism. In someone whose primary killing system (the NADPH oxidase burst) is already broken, catalase-positive microbes face virtually no opposition.
The most frequent bacterial culprits include Staphylococcus aureus, Serratia marcescens, Burkholderia cepacia, Nocardia species, and Salmonella. Fungal infections, particularly from Aspergillus mold, are a leading cause of serious illness and death. A nationwide French study of adult CGD patients found that nine of ten deaths during follow-up were caused by infections, including cerebral abscesses from Aspergillus and Klebsiella, disseminated fungal disease, and bloodstream infections from Burkholderia.
How CGD Is Diagnosed
The standard screening test is called the DHR (dihydrorhodamine 123) flow cytometry assay. A blood sample is drawn and the neutrophils are stimulated in the lab. In healthy cells, the respiratory burst converts a fluorescent dye, making the cells glow brightly under a detector. In CGD, the cells stay dim because no burst occurs. This test is highly accurate, correlates well with older methods, and can also identify carriers of X-linked CGD who may have a mixed population of working and non-working neutrophils.
Once abnormal DHR results confirm the diagnosis, genetic testing identifies which specific gene is mutated. This step is important for predicting the disease course, guiding treatment decisions, and providing genetic counseling to the family.
Daily Management and Preventing Infections
Because the immune defect is permanent (unless cured by transplant or gene therapy), people with CGD take daily preventive medications for life. The standard regimen includes a daily antibiotic, typically trimethoprim-sulfamethoxazole, to reduce the risk of bacterial infections, and a daily antifungal, usually itraconazole, to guard against mold and yeast. Together, these prophylactic medications dramatically reduce the frequency of serious infections.
A third component of standard care is interferon gamma, an immune-boosting protein given by injection. A landmark clinical trial in the New England Journal of Medicine showed that interferon gamma cut the number of serious infections by roughly two-thirds: only 14 of 63 patients on interferon experienced a serious infection, compared to 30 of 65 patients on placebo. The time to first serious infection was also significantly longer. Interferon gamma does not fix the NADPH oxidase defect, and its exact mechanism in CGD is still debated, but the clinical benefit is well established.
Beyond medications, people with CGD need to avoid specific environmental exposures. Mulch, compost piles, construction dust, and marijuana smoke are rich sources of Aspergillus spores and can trigger life-threatening lung infections. Swimming in freshwater lakes or poorly maintained pools also carries higher risk.
Life Expectancy and Long-Term Outlook
Outcomes have improved enormously over the past few decades. In the 1980s, the median life expectancy for someone with CGD was about 10 years. With modern prophylactic antibiotics, antifungals, and interferon gamma, it now exceeds 30 years. Many patients reach adulthood and live well into middle age, though the risk of serious infection never fully disappears. In a French cohort of adult patients, the median age at death for those who did not survive was 24.3 years, but many others in the same cohort remained alive and stable through follow-up.
Chronic inflammation also takes a toll over time. CGD-related inflammatory bowel disease resembles Crohn’s disease and can cause persistent diarrhea, abdominal pain, and poor growth in children. Granulomas in the urinary tract can cause obstruction. These inflammatory complications sometimes require immunosuppressive treatment, which creates a delicate balancing act in someone already prone to infection.
Stem Cell Transplant as a Cure
Hematopoietic stem cell transplant (bone marrow transplant) is currently the only widely available cure for CGD. The procedure replaces the patient’s defective immune cells with healthy donor cells capable of producing a functional NADPH oxidase. A large multicenter study of 712 patients transplanted between 1993 and 2018 reported an overall survival rate of 85.7% at three years. Among survivors, 84% achieved complete replacement of their myeloid (infection-fighting) cells with donor-derived cells.
Transplant outcomes are best when performed early in life, before serious infections or organ damage accumulate, and when a well-matched donor is available. The procedure carries real risks, including graft failure and graft-versus-host disease, so the decision involves weighing the long-term dangers of CGD against the short-term risks of transplant.
Gene Therapy: A Newer Option
For patients without a suitable donor, gene therapy offers a potential alternative. Instead of replacing the immune system with a donor’s cells, gene therapy corrects the patient’s own stem cells by inserting a working copy of the defective gene. In initial clinical trials for X-linked CGD, nine severely affected patients received gene-corrected stem cells after chemotherapy conditioning. Six of the seven surviving patients maintained stable levels of functional neutrophils at 12 months, with 16% to 46% of their neutrophils producing a normal oxidative burst. None of these patients developed new CGD-related infections during follow-up, and six were able to stop their prophylactic antibiotics and antifungals entirely. Three patients have been followed for up to three years with sustained correction and no signs of the genetic instability that plagued earlier gene therapy approaches.