Chronic Granulomatous Disease - CGD

Diagnosis

Indications for Testing

Laboratory Testing

  • Neutrophil oxidative burst assay (DHR) via flow cytometry
    • Preferred screening test
    • Disease is indicated by absence or significant alteration of activity
  • Other, less reliable tests
    • Measurement of superoxide production, ferricytochrome C reduction, nitroblue tetrazolium test
  • Nonspecific testing to rule out other disorders
    • Serum quantitative immunoglobulins – rule out hypogammaglobulinemia
    • Complement activity enzyme immunoassay – rule out complement deficiency
    • CBC with differential – rule out other causes of chronic infection (eg, neutropenic disorders)
    • Leukocyte adhesion deficiency panel – rule out leukocyte adhesion deficiency
  • Genetic testing
    •  X-linked chronic granulomatous disease (CGD) – CYBB gene
    • Autosomal recessive CGD – NCF1, NCF2, NCF4, CYBA genes

Differential Diagnosis

Clinical Background

Chronic granulomatous disease (CGD) is an inherited primary immunodeficiency disorder characterized by severe, recurring infections with formation of granulomas. Phagocytic cells ingest but cannot digest bacteria or fungi due to a malfunction of the nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase system.

Epidemiology

  • Incidence – 1/250,000 births
  • X-linked CGD
    • CYBB – 60-70% of cases
  • Autosomal recessive CGD
    • NCF1 – 25% of cases
    • CYBA – <5% of cases
    • NCF2 – <5% of cases
    • NCF4 – very rare
  • Age – dependent on type of CGD
    • Classic X-linked in males – typically <3 years
    • Carrier females of X-linked – usually >3 years
    • Females with skewed X-chromosome inactivation – similar to males
  • Sex – M>F by 85%

Inheritance

  • X-linked form – 60-70% of cases
    • Involves CYBB gene mutations in the 13 exons encoding the 91-kD heavy chain of cytochrome b558
      • Typically earlier onset and more severe disease than autosomal recessive CGD
  • Autosomal recessive forms
    • NCF1 – encodes p47-phox
      • GT deletion in exon 2 accounts for majority of mutations
    • CYBA – encodes p22-phox
    • NCF2 – encodes p67-phox
    • NCF4 – encodes p40-phox

Pathophysiology

  • Function of phagocytes (neutrophils and macrophages)
    • First line of defense against bacterial and fungal infections
    • Migrate to the site of infection – phagocytosis occurs, which generates microbicidal reactive oxygen products
    • Neutrophils and macrophages are ingested by the phagosome
    • Other nonoxidative factors are added that assist in killing pathogenic microorganisms
  • CGD – abnormalities of neutrophils and macrophages
    • Gene mutations cause defective microbicidal oxidant production secondary to a defect in the neutrophil respiratory burst
    • Results in decreased production of superoxide, hydrogen peroxide, hydroxyl radical, and hypochlorite ions within neutrophils and macrophages
      • Defective production causes susceptibility to infections from organisms that may be nonpathogenic in an immunocompetent individual
      • Most common infections – bacterial (eg, catalase-positive microorganisms) and fungal organisms

Clinical Presentation

  • Signs and symptoms usually appear very early in childhood
    • May not present until later in life, especially with mild cases or autosomal recessive/variant forms of X-linked CGD
  • Ophthalmic – chorioretinitis
  • Gastrointestinal – nausea, diarrhea, vomiting, colitis/enteritis with inflammatory bowel disease (IBD)-like manifestations (blood in stool, granulomas in gastrointestinal tract), splenomegaly
  • Genitourinary – urethral strictures, bladder granulomas
  • Pulmonary – pneumonia 
  • Skin and musculoskeletal – lymphadenitis, skin and visceral abscesses, osteomyelitis
  • Infections
    • Chronic obstructive granulomas form at sites of infection
    • Characterized by bacterial and fungal infections, with most common agents including
      • Staphylococcus aureus
      • Burkholderia cepacia
      • Serratia marcescens
      • Nocardia spp
      • Aspergillus spp

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Neutrophil Oxidative Burst Assay (DHR)  0096657
Method: Semi-Quantitative Flow Cytometry

Functional assay for screening for CGD

Results alone are not diagnostic

Specimen must remain ambient and be tested within 48 hours of collection

With abnormal result, consider genetic testing

Chronic Granulomatous Disease (CYBB Gene Scanning and NCF1 Exon 2 GT Deletion) with Reflex to CYBB Sequencing 2006356
Method: Polymerase Chain Reaction/High Resolution Melt Analysis

Preferred test to confirm a clinical or laboratory diagnosis of CGD and assess for carrier status of CGD

Predictive testing for unaffected at-risk relatives

Clinical sensitivity – 86% for CGD

Analytical sensitivity – 99% for CYBB or homozygous NCF1 GT deletion; 90% for heterozygous NCF1 GT deletion

Analytical specificity – 99%

Diagnostic errors can occur due to rare sequence variations

Deep intronic mutations in CYBB, mutations in NCF1 other than the GT deletion in exon 2, and mutations in additional genes associated with CGD are not evaluated

Large CYBB gene deletions/duplications will not be detected in females

Breakpoints of large CYBB deletions/duplications will not be determined in males

Lack of GT deletion in exon 2 does not rule out carrier status due to potential recombination between NCF1 and its pseudogenes

 
Chronic Granulomatous Disease (NCF1) Exon 2 GT Deletion 2006366
Method: Polymerase Chain Reaction/High Resolution Melt Analysis

Tests for a common NCF1 mutation associated with autosomal recessive CGD

Diagnostic errors can occur due to rare sequence variations

Mutations in NCF1 other than the GT deletion in exon 2, and mutations in additional genes associated with CGD are not evaluated

Lack of GT deletion in exon 2 does not rule out carrier status due to potential recombination between NCF1 and its pseudogenes

 
Chronic Granulomatous Disease, X-Linked (CYBB) Gene Scanning with Reflex to Sequencing 2006361
Method: Polymerase Chain Reaction/High Resolution Melt Analysis

Molecular test to confirm a diagnosis or assess carrier status for X-linked CGD

Diagnostic errors can occur due to rare sequence variations

Deep intronic mutations in CYBB and mutations in additional genes associated with CGD are not evaluated

Large CYBB gene deletions/duplications will not be detected in females

Breakpoints of large CYBB deletions/duplications will not be determined in males

 
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Immunoglobulins (IgA, IgG, IgM), Quantitative 0050630
Method: Quantitative Nephelometry

Initial test in workup of immunoglobulin disorders

In adults and older children with suspected hypogammaglobulinemia, order in conjunction with serum protein electrophoresis and immunofixation

Panel includes IgA, IgG, IgM

Complement Activity Enzyme Immunoassay, Total 0050198
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Rule out complement deficiency

CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Rule out other causes of chronic infection, including anemia

Leukocyte Adhesion Deficiency Panel 2004359
Method: Semi-Quantitative Flow Cytometry

Rule out leukocyte adhesion deficiency

Panel measures CD11b, CD15, and CD18 on neutrophils

Familial Mutation, Targeted Sequencing 2001961
Method: Polymerase Chain Reaction/Sequencing

Useful when a familial mutation identifiable by sequencing is known