HTT and Alzheimer disease: Furthermore, Alzheimer’s disease (AD), TTR-FAP and familial amyloid cardiomyopathy caused by hereditary transthyretin amyloidosis belong to amyloid-related illnesses, whereas Huntington’s (HD) and Parkinson’s disease (PD) are linked to intracellular aggregation of another misfolded proteins – huntingtin and alpha-synuclein, respectively.