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Alpha1-antitrypsin deficiency with M-like phenotype
Abstract:
A patient with a low serum concentration of alpha1-antitrypsin (0-1 g/l) but with an M-like phenotype is described. Her parents and 2 sibs have a PIM phenotype, but all except the father have approximately half-normal levels of alpha1-antitrypsin: The M-like variant apparently cannot be distinguished from M-alpha1-antitrypsin, when it occurs with M in heterozygotes. The proposita has severe airways obstruction and emphysema, and her father has moderate chronic obstructive pulmonary disease. The mother and 2 sibs are healthy.
Insights
A rare alpha1-antitrypsin variant, indistinguishable from M-alpha1-antitrypsin in heterozygotes, is linked to severe lung disease. This finding highlights the importance of genetic screening for alpha1-antitrypsin deficiency.
Area of Science:
- Pulmonology
- Clinical Genetics
- Biochemistry
Background:
- Alpha1-antitrypsin deficiency (AATD) is a genetic disorder that increases the risk of lung and liver disease.
- The most common deficiency allele is Z, but other rare alleles exist.
- Phenotypic analysis of alpha1-antitrypsin (AAT) is crucial for diagnosing AATD.
Observation:
- A patient presented with severe airways obstruction and emphysema, despite an M-like AAT phenotype, and had low serum AAT concentrations (0-1 g/l).
- Her parents and siblings exhibited the PIM phenotype, with approximately half-normal AAT levels in all but the father.
- The M-like variant was indistinguishable from M-AAT in heterozygotes.
Findings:
- The M-like variant, when co-inherited with the M allele, results in low serum AAT levels and severe pulmonary disease in the proposita.
- Family members with the PIM phenotype and reduced AAT levels showed varying degrees of lung disease or remained asymptomatic.
- This case suggests that certain M-like variants can cause AATD and associated lung pathology.
Implications:
- Accurate identification of AAT variants is critical for predicting disease risk and guiding genetic counseling.
- The study underscores the need for comprehensive AAT phenotyping and genotyping, especially in patients with unexplained obstructive lung disease.
- Further research into rare AAT variants is necessary to fully understand their clinical significance and associated disease spectrum.