An unusual case of alpha-1-antitrypsin deficiency: SZ/Z. 2019

M D Speevak, and M L DeMarco, and N S Wiebe, and K R Chapman
Department of Laboratory Medicine and Pathobiology, University of Toronto, Canada. Electronic address: marsha.speevak@thp.ca.

A female patient was first seen at age 65 due to a diagnosis of alpha-1-antitrypsin deficiency (AATD). She was a lifelong non-smoker, with no significant history of second hand smoke exposure. There was no prior family history of AATD or liver disease. Her serum AAT concentration was measured on two occasions and in both cases, concentration was <0.21 g/L. The patient was referred for genetic testing to determine her SERPINA1 (the gene responsible for AATD) genotype. Three deficiency alleles were identified: she was heterozygous for S, a mild deficiency allele, and homozygous for Z, a severe deficiency allele. This case represents unusual convergence of three pathogenic SERPINA1 variants in a single individual. We report the investigations used to clarify her unusual genotype and propose non-crossover gene conversion as the likely mechanism.

UI MeSH Term Description Entries
D005260 Female Females
D005785 Gene Conversion The asymmetrical segregation of genes during replication which leads to the production of non-reciprocal recombinant strands and the apparent conversion of one allele into another. Thus, e.g., the meiotic products of an Aa individual may be AAAa or aaaA instead of AAaa, i.e., the A allele has been converted into the a allele or vice versa. Polar Recombination,Polaron,Conversion, Gene,Conversions, Gene,Gene Conversions,Polar Recombinations,Polarons,Recombination, Polar,Recombinations, Polar
D005820 Genetic Testing Detection of a MUTATION; GENOTYPE; KARYOTYPE; or specific ALLELES associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Genetic Predisposition Testing,Genetic Screening,Predictive Genetic Testing,Predictive Testing, Genetic,Testing, Genetic Predisposition,Genetic Predictive Testing,Genetic Screenings,Genetic Testing, Predictive,Predisposition Testing, Genetic,Screening, Genetic,Screenings, Genetic,Testing, Genetic,Testing, Genetic Predictive,Testing, Predictive Genetic
D005838 Genotype The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS. Genogroup,Genogroups,Genotypes
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000368 Aged A person 65 years of age or older. For a person older than 79 years, AGED, 80 AND OVER is available. Elderly
D000483 Alleles Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product. Allelomorphs,Allele,Allelomorph
D000515 alpha 1-Antitrypsin Plasma glycoprotein member of the serpin superfamily which inhibits TRYPSIN; NEUTROPHIL ELASTASE; and other PROTEOLYTIC ENZYMES. Trypsin Inhibitor, alpha 1-Antitrypsin,alpha 1-Protease Inhibitor,alpha 1-Proteinase Inhibitor,A1PI,Prolastin,Serpin A1,Zemaira,alpha 1 Antiprotease,alpha 1-Antiproteinase,1-Antiproteinase, alpha,Antiprotease, alpha 1,Inhibitor, alpha 1-Protease,Inhibitor, alpha 1-Proteinase,Trypsin Inhibitor, alpha 1 Antitrypsin,alpha 1 Antiproteinase,alpha 1 Antitrypsin,alpha 1 Protease Inhibitor,alpha 1 Proteinase Inhibitor
D019896 alpha 1-Antitrypsin Deficiency Deficiency of the protease inhibitor ALPHA 1-ANTITRYPSIN that manifests primarily as PULMONARY EMPHYSEMA and LIVER CIRRHOSIS. Deficiencies, alpha 1-Antitrypsin,Deficiency, alpha 1-Antitrypsin,alpha 1 Antitrypsin Deficiency,alpha 1-Antitrypsin Deficiencies

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