Proteins constantly fold and unfold in vivo. Molecular chaperones help to ensure that a protein's final three-dimensional assembly is correct, but mistakes happen. If proteins assume unnatural conformations, they can cause any one of a family of diseases called amyloidoses, in which misfolded peptides accumulate in or around cells, forming aggregates. Most symptoms associated with systemic amyloidoses are due to the physical build-up of these amyloid deposits in vital organs.