**Core Concept**
Transthyretin (TTR) amyloidosis is a hereditary condition characterized by the deposition of abnormal transthyretin protein in various tissues, leading to organ dysfunction. This condition is caused by mutations in the transthyretin gene, which encodes the TTR protein responsible for transporting thyroid hormones and vitamin A in the blood.

**Why the Correct Answer is Right**
Mutations in the transthyretin gene disrupt the normal structure and function of the TTR protein, leading to its misfolding and aggregation into amyloid fibrils. These fibrils deposit in tissues such as the heart, nerves, and kidneys, causing damage and organ dysfunction. The most common mutations associated with TTR amyloidosis are Val30Met and Leu55Pro, which are inherited in an autosomal dominant pattern.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because AL amyloidosis is caused by a plasma cell dyscrasia, leading to the deposition of lambda or kappa light chain immunoglobulin in tissues.
**Option B:** This option is incorrect because AA amyloidosis is caused by chronic inflammation or infection, leading to the deposition of serum amyloid A protein in tissues.
**Option C:** This option is incorrect because ATTR2 amyloidosis is caused by the wild-type transthyretin protein, which is not associated with mutations in the transthyretin gene.

**Clinical Pearl / High-Yield Fact**
TTR amyloidosis is a hereditary condition that can be diagnosed by genetic testing for mutations in the transthyretin gene. Early diagnosis and treatment can prevent organ damage and improve patient outcomes.

**Correct Answer: C. Transthyretin amyloidosis**