Alpha 1 antitrypsin deficiency mechanism of transmission ?
**Core Concept**
Alpha 1 antitrypsin deficiency is a genetic disorder characterized by the deficiency of alpha 1 antitrypsin (A1AT), a serine protease inhibitor produced in the liver. The deficiency leads to the accumulation of abnormal A1AT protein in the liver, resulting in liver damage and increased risk of pulmonary emphysema.
**Why the Correct Answer is Right**
The mechanism of transmission of alpha 1 antitrypsin deficiency is autosomal codominant, meaning that both parents can be carriers of the mutated gene and pass it to their offspring. The deficiency is caused by mutations in the SERPINA1 gene, which encodes the A1AT protein. The most common mutation is the ZZ mutation, which leads to the production of a dysfunctional A1AT protein. The ZZ mutation is inherited in an autosomal codominant pattern, with each parent contributing one copy of the mutated gene to their offspring.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the mechanism of transmission of alpha 1 antitrypsin deficiency is not X-linked recessive, as it affects both males and females equally.
**Option B:** This option is incorrect because the deficiency is not caused by a single dominant mutation, but rather by the accumulation of abnormal A1AT protein due to the ZZ mutation.
**Option C:** This option is incorrect because the deficiency is not caused by a viral infection, but rather by a genetic mutation.
**Clinical Pearl / High-Yield Fact**
Alpha 1 antitrypsin deficiency is often diagnosed in adulthood, when symptoms of pulmonary emphysema or liver disease become apparent. However, newborn screening programs can detect the deficiency early, allowing for early intervention and treatment.
**Correct Answer:** D. Autosomal codominant inheritance.