Senile cardiac amyloidosis associated protein is ?
**Core Concept**
Senile cardiac amyloidosis is a condition characterized by the deposition of amyloid fibrils in the heart, leading to restrictive cardiomyopathy. This condition is associated with aging and is more common in individuals over 60 years old. The amyloid protein deposited in the heart is a key factor in the pathogenesis of this disease.
**Why the Correct Answer is Right**
The amyloid protein associated with senile cardiac amyloidosis is transthyretin (TTR). TTR is a transport protein produced by the liver that normally helps to carry thyroid hormones and vitamin A in the blood. In senile cardiac amyloidosis, wild-type TTR is deposited in the heart, leading to the formation of amyloid fibrils that disrupt normal cardiac function. This deposition is thought to be related to the accumulation of TTR in the heart over time, possibly due to a decrease in its clearance.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a protein. While amyloidosis can be caused by various proteins, the question specifically asks for the protein associated with senile cardiac amyloidosis.
**Option B:** This option is incorrect because it is associated with primary amyloidosis, also known as AL amyloidosis, which is caused by the deposition of light chain immunoglobulins produced by plasma cells.
**Option C:** This option is incorrect because it is associated with secondary amyloidosis, also known as AA amyloidosis, which is caused by chronic inflammation and the deposition of serum amyloid A (SAA) protein.
**Clinical Pearl / High-Yield Fact**
Senile cardiac amyloidosis is often associated with a characteristic ECG pattern known as a "low-voltage QRS complex", which is a result of the amyloid deposition in the heart. This pattern can be a useful diagnostic clue in patients with unexplained cardiomyopathy.
**Correct Answer: D. Transthyretin (TTR)**