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'SZ like' alpha 1-antitrypsin phenotypes in PI ZZ children with liver disease

D B Whitehouse1, J U Lovegrove, G Mieli-Vergani

  • 1MRC Human Biochemical Genetics Unit, Galton Laboratory, London.

Annals of Human Genetics
|January 1, 1994
PubMed

Insights

High-resolution isoelectric focusing revealed variable alpha-1-antitrypsin (AAT) Z patterns in PI ZZ individuals. An "SZ-like" pattern, mimicking the SZ phenotype, was more common in liver disease patients, potentially causing misclassification.

Area of Science:

  • Medical Genetics
  • Biochemistry
  • Pulmonology

Background:

  • Alpha-1-antitrypsin (AAT) deficiency (PI ZZ genotype) is linked to liver and lung diseases.
  • Accurate phenotyping is crucial for understanding disease associations and genetic counseling.
  • Isoelectric focusing (IEF) is a standard method for AAT phenotyping.

Purpose of the Study:

  • To investigate the variability of AAT Z phenotypes in individuals with the PI ZZ genotype.
  • To determine if specific patterns are associated with liver or chest disease.
  • To assess the potential for misclassification due to 'SZ-like' patterns.

Main Methods:

  • High-resolution isoelectric focusing (IEF) was used to analyze AAT phenotypes.
  • 106 individuals with the PI ZZ genotype were studied: 71 with liver disease, 22 with chest disease, and 13 healthy controls.
  • IEF patterns were categorized based on staining intensity of acidic and basic isoforms.

Main Results:

  • AAT Z patterns exhibited significant variability among PI ZZ individuals.
  • The majority (89/106) showed maximum staining in basic isoforms.
  • A distinct 'SZ-like' pattern, with intensified acidic isoforms, was observed in 17 individuals, more frequently in the liver disease group (16/71).

Conclusions:

  • The 'SZ-like' AAT phenotype pattern is a notable variant within the PI ZZ genotype.
  • This pattern's higher prevalence in liver disease patients suggests a potential genotype-phenotype correlation.
  • Misidentification of 'SZ-like' patterns as the genuine SZ phenotype could lead to overestimation of PI SZ-associated childhood liver disease incidence.

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