SPECIFIC GRANULE DEFICIENCY
 
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SPECIFIC GRANULE DEFICIENCY

 

DEFINITION:

A disorder of neutrophil function characterized by dysfunctional specific granules resulting in chronic and recurrent skin and lung infections and abscesses.

EPIDEMIOLOGY:

  • incidence: very rare (about 5 families worldwide)
  • age of onset:
    • first few years of life
  • risk factors:
    • familial - autosomal recessive
      • chrom.#: ?
      • gene: ?

PATHOGENESIS:

1. Background

  • neutrophils contain two distinct sets of granules: azurophils and specific

    1. Specific Granules

    • peroxidase negative
    • form during the later phases of myelocyte differentiation and maturation to the metamyelocyte and band stage
    • contain unique bactericidal proteins
      • lysozyme, lactoferrin, cytochrome b
    • contain unique acid hydrolases and neutral proteinases
      • collagenase, plasminogen activator, Vitamin B12-binding protein

2. Genetic Defect

  • genetic defect -> failure of specific granules to form in developing myeloid precursors in the bone marrow -> decreased chemotaxis and bacterial killing of neutrophils -> recurrent and chronic skin and lung infections and abscesses
  • may also be a deficiency of defensins in the azurophils in this condition
  • S. aureus, gram negative bacteria, and C. albicans most frequently isolated from lesions

CLINICAL FEATURES:

1. Recurrent Infections

  • chronic and recurrent skin ulcers and abscesses
  • chronic and recurrent lung infections and abscesses
  • recurrent episodes of bronchopneumonia, chronic cough
  • recurrent lymphadenitis, otitis media, and mastoiditis

INVESTIGATIONS:

1. CBC

  • 2,000-15,000 WBC's (50-70% PMN's)

2. Neutrophil Function

  • chemotaxis - decreased
  • superoxide release - decreased due to lack of cytochrome b
  • bacterial killing
    • decreased due to lack of defensins and lactoferrin

3. Cytochemistry (Wright Stain)

  • bilobed nuclei in >80% of neutrophils
  • striking decrease in cytoplasmic granularity due to lack of specific granules
  • absence of alkaline phosphatase and lactoferrin

MANAGEMENT:

1. Supportive

  • management of infections and abscesses
    • appropriate antibiotics and antifungal agents
    • drain abscesses
  • genetic counselling

 

 

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