Familial amyloid polyneuropathy

Familial amyloid polyneuropathy, also called transthyretin-related hereditary amyloidosis, transthyretin amyloidosis abbreviated also as ATTR (hereditary form), or Corino de Andrade's disease, is an autosomal dominant neurodegenerative disease. It is a form of amyloidosis, and was first identified and described by Portuguese neurologist Mário Corino da Costa Andrade, in 1952. FAP is distinct from senile systemic amyloidosis (SSA), which is not inherited, and which was determined to be the primary cause of death for 70% of supercentenarians who have been autopsied. FAP can be ameliorated by liver transplantation. Usually manifesting itself between 20 and 40 years of age, it is characterized by pain, paresthesia, muscular weakness and autonomic dysfunction. In its terminal state, the kidneys and the heart are affected. FAP is characterized by the systemic deposition of amyloidogenic variants of the transthyretin protein, especially in the peripheral nervous system, causing a progressive sensory and motor polyneuropathy. FAP is caused by a mutation of the TTR gene, located on human chromosome 18q12.1-11.2. A replacement of valine by methionine at position 30 (TTR V30M) is the mutation most commonly found in FAP. The transthyretin protein is a tetramer. The tetramer has to dissociate into misfolded monomers to aggregate into a variety of structures including amyloid fibrils. Because most patients are heterozygotes, they deposit both mutant and wild type TTR subnits. FAP is inherited in an autosomal dominant manner. This means that the defective gene responsible for the disorder is located on an autosome (chromosome 18 is an autosome), and only one copy of the defective gene is sufficient to cause the disorder, when inherited from a parent who has the disorder. Clinical suspicion for FAP is raised on the basis of a family history of neuropathy and physical exam showing signs of neuropathy. Diagnosis can be made using genetic testing to identify mutations in the TTR gene, but may include other corroborative investigation.