This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Protein deposited in familial amyloid neuropathy: 
Select and explain. 
A. Mutated transthyretin, B. Normal transthyretin, C. Mutated β2, D. Normal β2
A: Mutated transthyretin
Answer: A: Mutated transthyretin 
Explanation: "Transthyretin (TTR) is a normal serum protein that binds and transports thyroxine and retinol, hence the name trans-thy-retin.
A mutant form of transthyretin (and its fragments) is deposited in a group of genetically determined disorders referred to as familial amyloid polyneuropathies. Several mutations have been identified in the transthyretin protein that contributes to its deposition in tissues in the form of amyloid. Transthyretin is also deposited in the heart of aged individuals (senile systemic amyloidosis), but in such cases, the transthyretin molecule is structurally normal.
                                 Table: Classification of Amyloidosis