Alpha-1 antitrypsin deficiency is a hereditary ailment arising from mutations in the SERPINA1 gene, which directs the synthesis of alpha-1 antitrypsin protein. This condition follows an autosomal codominant inheritance pattern, where two distinct variants of the gene are active and contribute to the genetic trait. The most prevalent variant (allele) of SERPINA1 gene, M allele, generates normal levels of alpha-1 antitrypsin while Z allele is a common subtype responsible for causing alpha-1 antitrypsin deficiency.
Each individual inherits two copies of the gene for alpha-1 antitrypsin, one from each parent. The majority of people possess two unaltered copies of the alpha-1 antitrypsin gene. However, those with alpha-1 antitrypsin deficiency harbor one functional and one impaired copy, which may consist of either the Z or S allele[2][9]. The ZZ genotype denotes the most severe manifestation of alpha-1 antitrypsin deficiency, whereas individuals carrying an MZ genotype present a milder form[9].
In the event that both parents possess the flawed gene, their offspring hold a 25% likelihood of acquiring two faulty copies of said gene and consequently developing alpha-1 antitrypsin deficiency[1]. On the other hand, if one parent suffers from alpha-1 antitrypsin deficiency while the other does not, their progeny shall inherit one impaired copy of this gene and serve as carriers of this condition[9].
To summarize, alpha-1 antitrypsin deficiency is a hereditary ailment that arises from mutations in the SERPINA1 gene. The mode of inheritance follows an autosomal codominant pattern, whereby individuals who carry one normal and one mutated copy of the gene can become carriers of the condition. In cases where both parents are carriers of the defective gene, their offspring has a 25% likelihood of acquiring two damaged copies of the gene and thus developing alpha-1 antitrypsin deficiency.
Citations:
[1] https://medlineplus.gov/genetics/condition/alpha-1-antitrypsin-deficiency/
[2] https://www.genome.gov/Genetic-Disorders/Alpha-1-Antitrypsin-Deficiency
[3] https://learn.genetics.utah.edu/content/genetics/alpha1
[4] https://www.ncbi.nlm.nih.gov/books/NBK1519/
[5] https://www.ncbi.nlm.nih.gov/books/NBK442030/
[6] https://rarediseases.org/rare-diseases/alpha-1-antitrypsin-deficiency/
[7] https://bestpractice.bmj.com/topics/en-us/1075
[8] https://ojrd.biomedcentral.com/articles/10.1186/1750-1172-3-16
[9] https://www.asthmaandlung.org.uk/conditions/alpha-1-antitrypsin-deficiency/what-cause-alpha-1-antitrypsin-deficiency
