Immunodeficiency Search

CHRONIC GRANULOMATOUS DISEASE

SUMMARY

1. Chronic granulomatous disease is a phagocyte immunodeficiency syndrome caused by mutations in the NADPH oxidase complex.

2. Most mutations are X-linked while four types of autosomal recessive CGD have been described.

3. CGD patients typically experience severe infections with catalase positive organisms. Pneumonia, skin abscess, lymphadenitis, liver abscess, and osteomyelitis are common infectious complications.

4. The main pathogens causing infections in North American CGD patients are Staph aureus, Burkholderia cepacia, Serratia, Nocardia, and Aspergillus.

5. Non-infectious complications include colitis, obstructive granulomas in the GI and GU tract, and autoimmune diseases such as SLE.

6. Diagnosis is based on demonstration of defective oxidative burst (DHR assay or NBT) followed by genetic testing for mutations.

7. Recent data indicate that resedual reactive oxygen intermediate (ROI) production in patients is associated with significantly less severe illness and a greater likelihood of long-term survivalthan patients with little residual ROI production.

8. Bactrim and Itraconazole daily prophylaxis and prompt aggressive treatment of infections have been keys to prolonging the lives of patients.

9. Stem cell transplantation should be considered for patients with minimal ROI production and recurrent severe infections despite antimicrobial prophylaxis.

OVERVIEW

Chronic Granulomatous Disease (CGD) is characterized by defective intracellular bacterial and fungal killing in neutrophils and monocytes. It is caused by defects in NADPH oxidase, the enzyme complex responsible for generating the phagocyte respiratory burst. The most common types of infections are skin abscesses, pneumonia, lymphadenitis, liver abscess, and osteomyelitis. Organisms that are catalase negative are killed normally whereas catalase positive organisms can cause severe deep-seated infections (see list below). There are both X-linked and autosomal recessive forms of disease. In general, patients with X-linked CGD present at an earlier age and have a more severe clinical course. Granuloma formation occurs in CGD when microbes are ingested by neutrophils but cannot be destroyed. This results in sustained presentation of microbial antigens to CD4 T-cells which mediate a chronic inflammatory response.

Inflammatory bowel disease resulting in malabsorption can be seen in patients (particulary in X-linked CGD). Obstructive GI tract and urinary tract granulomas are problematic complications. Liver abnormalities include elevated liver enzymes with biopsies showing granulomata and lobar hepatitis. Development of portal hypertension and thrombocytopenia is a very poor prognostic sign in patients.

Autoimmune features include systemic lupus erythematosus in CGD patients as well as X-linked CGD female carriers. Other conditions reported at higher frequency in CGD patients include sarcoidosis, idiopathic thrombocytopenic purpura (ITP), and Juvenile idiopathic arthritis (JIA).

The main catalase positive organisms causing infections in CGD patients are listed below:

-Staphylococcus aureus

-Aspergillus

-Burkholderia cepacia

-Serratia marcescens

-Nocardia

-Chromobacterium violaceum

-Granulibacter bethesdensis

-Klebsiella

-Atypical Mycobacteria

-Paecilomyces

PATHOGENESIS

CGD is caused by defects in the NADPH oxidase system which consists of 6 proteins (2 membrane bound and 4 cytosolic). Upon cellular activation, the cytosolic components assemble with the membrane bound components to form the active complex. Mutations in the membrane bound gp91phox (CYBB gene) causes X-linked CGD; this accounts for 65-70% of all cases. Mutations in the other membrane bound component p22phox (CYBA gene) cause a form of autosomal recessive CGD (5% of cases). Cytosolic p47phox is encoded for by the NCF1 gene and accounts for 25% of cases. The cytosolic p67phox encoded by the NCF2 gene accounts for approximately 5% of cases. Finally, a mutation in p40phox encoded by the NCF4 gene has been described in a single patient.

It was previously believed that reactive oxygen species generated from superoxide were the main bactericidal molecules. However, more recent evidence suggests that the generation of superoxide stimulates an influx of potassium cations into the cell which then activate the release of neutrophil proteases (neutrophil elastase and cathepsin G). Support for this paradigm comes from the observation that patients with myeloperoxidase deficiency are typically asymptomatic and neutrophil protease deficient mice have significantly increased susceptibility to S. Aureus and C. Albicans despite being able to generate reactive oxygen species.

DIFFERENTIAL DIAGNOSIS

- Other chromosomal breakage syndromes (Nijmegen breakage syndrome, bloom syndrome)

- Other causes of ataxia (cerebral palsy, tumors, infectious processes)

- Dyskeratosis congenita - Hoyeraal-Hreidarsson variant (this can be associated with immunodeficiency, cerebellar hypoplasia, and neurologic delay)

EVALUATION

Step 1: Screening Studies

Testing for CGD involves first testing for neutrophil function. Two types of tests are available. The DHR assay is clearly the preferred test. The NBT test is quickly becoming obsolete.

Dihydrorhodamine 123 (DHR) assay:

-In this test, DHR is taken up by phagocytes. The phagocytes are then activated and superoxide production leads to oxidation of DHR and generation of fluorescence that can be detected by flow cytometry.

-This quantitative assay allows for differentiation between X-linked, autosomal recessive, and X-linked carriers of disease.

-Nitroblue tetrazolium (NBT) test)

-This is one of the oldest tests available for testing neutrophil function. Yellow NBT is reduced to blue by superoxide production by phagocytes. The blue change is visualized under light microscopy by an operator.

-Disadvantages of this test include operator subjectivity and false negatives. X-linked carriers may be identified with this test but a distinction between X-linked and autosomal recessive CGD cannot be made.

Step 2: Gene Sequencing

Testing showing decreased neutrophil function should be followed by specific genetic testing. Often a family history of affected males on the maternal side of the family (X-linked) or a history of consanguinity (AR) can be useful in directing specific testing.

1.gp91phox (CYBB gene) X-linked

2.p22phox (CYBA gene) AR

3.p47phox (NCF1 gene) AR

4.p67phox (NCF2 gene) AR

MANAGEMENT

CGD was initially termed fatal granulomatous disease of childhood with most patients not surviving past their first decade of life. Currently the majority of patients are expected to survive to adulthood. The two main principles that have resulted in increased patient survival are antibacterial/antifugal prophylaxis and aggressive management of infections.

A. PROPHYLAXIS: The following lifelong prophylactic regimens should be started for all patients:

1. Trimethoprim-sulfamethoxazole (TMP-SMX) 5mg/kg/day (based on TMP component) up to a maximum of 320mg.

**Dicloxacillin or fluorquinolones are reasonable alternatives for patients who are allergic to sulfonamide drugs.

2. Itraconazole 5mg/kg once daily (maximum 200mg)

3. Interferon gamma (50mcg/m2 subcutaneously 3 times weekly) has demonstrated a reduction in the number of infections in a number of studies. For children less than 0.5 m2, 1.5 mcg/kg subcutaneously 3 times weekly is recommended. Fever and flu like symptoms are significant side effects that limit the use of this medication.

B. ACUTE TREATMENT: Identification of causative pathogens is essential for directing appropriate treatment.. When possible, diagnostic tissue biopsies should be obtained prior to initiation of empiric therapy. After cultures have been obtained, empiric treatment should include coverage for gram negative, gram positive, nocardia, and fungal pathogens. Empiric therapy for pneumonia may include TMP-SMX or Meropenem, Vancomycin, and Voriconazole. Treatment can be adjusted and narrowed based on culture results. The use of ESR/CRP and serial diagnostic imaging is useful for following response to therapy.

C. COLITIS TREATMENT: Colitis is usually responsive to oral prednisone therapy (1mg/kg/day). Relapses may occur after tapering and many patients may require long-term therapy. Inhibitors of TNF- are highly effective but associated with increased risk of life-threatening infections even with vigilant antimicrobial prophylaxis. Stem cell transplantation has resulted in resolution of colitis in patients.

D. GI AND GU OBSTRUCTION FROM GRANULOMA: Obstructive granulomas tend to be exquisitely sensitive to prednisone therapy (1mg/kg/day) for 1 week followed by a slow 6 week taper.

E. STEM CELL TRANSPLANTATION: Stem cell transplantation is a curative therapy for this disease in patients who have a fully matched donor. It is likely to be more successful early in life in patients who do not have end organ damage. However, this therapy has also been used in the setting of patients who suffer from recurrent severe infections and refractory inflammatory disease. The optimal conditioning regimen for patients has not been determined.

Recent data indicate that patients with chronic granulomatous disease and modest residual production of ROI have significantly less severe illness and a greater likelihood of long-term survival than patients with little residual ROI production. Thus, early HSCT may be a consideration for patients with no ROI production.

RESOURCES

Diagnostic Resources

1. DHR (Dihydrorhodamine) Assay:

This test is increasingly available at a number of testing sites. It is critical to have samples delivered to testing sites as soon as possible (neutrophils survive for only several hours - functional testing cannot be performed on dead cells).

a. Childrens Hospital Philadelphia Immunology Laboratory

b. Cincinnati Childrens Diagnostic Immunology Laboratory

c. ARUP Laboratories

2. Gene Sequencing (Gene Dx):

Testing for X-linked (CYBB) and three types of autosomal recessive (NCF1, NCF2, CYBA) CGD is commercially available. Testing typically takes 4-6 weeks.

Literature Resources

1. Winkelstein 2000

CGD U.S. Registry of 368 patients

2. Jones 2008

CGD patient registry in the United KIngdom

3. Seger 2008

Management of CGD review

4. Kang 2009

Advances in treatment of CGD

5. Segal 2002

Neutrophil killing mediated by K flux and proteases

6. Herbrecht 2002