**3.3 Transthyretin amyloid (ATTR) protein**

TTR is a transport protein made in the liver and choroid plexus. TTR transfers thyroxin and retinol in the blood and cerebrospinal fluid. TTR proteins can be differentiated into wild type and mutant type. TTR wild-type amyloid is associated with systemic senile amyloidosis and mostly affects heart ventricles in elderly patients. In this population, a prevalence of monoclonal gammopathy of undetermined significance (MGUS) has been reported [5]. TTR mutant type protein is related to hereditary amyloidosis. TTR mutant type protein can affect commonly peripheral nerves and other organs including the heart and gastrointestinal tract. This is inherited as an autosomal dominant pattern. The clinical course of TTR mutant type is relatively faster than TTR wild type in terms of onset and progression. Also, treatment and prognosis of two types are different. Therefore, distinguishing two types in early stage is important.
