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Amyloid disease in which deposited fibrils derive from immunoglobulin light chains. The precursor’s identity distinguishes it from amyloid formed from transthyretin or serum amyloid A.

Transthyretin is a secreted transport protein that forms a tetramer and carries thyroid hormones in blood plasma and cerebrospinal fluid. It also associates with retinol-binding protein, contributing to transport of vitamin A. The transported small molecule and the carrier have different roles: binding changes distribution and availability rather than turning the carrier into a thyroid hormone. ^[ref]

Transthyretin also illustrates the link between assembly and disease. Destabilization and misassembly can produce amyloid deposits. Functional transport by a soluble tetramer and accumulation of aggregated material are different molecular states, so detecting the same protein sequence does not establish that it remains in its normal assembly.

Disease caused by deposition of amyloid derived from transthyretin. Inherited variants and age-associated deposition of nonvariant protein distinguish different pathways to a similar fibrillar material.