Lambda II immunoglobulin light chain protein in primary localized rectal amyloidosis.

Rectal involvement is usually part of a systemic amyloidosis, whereas, localized rectal amyloidosis is a rare entity. We present a case of asymptomatic localized rectal amyloidoma. Amyloid fibrils were isolated from rectal biopsy tissue and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) which showed bands at 17 kDa, 21 kDa and 28 kDa, a broad doublet band at 7-8 kDa and weaker bands at 15 kDa and 24 kDa. Edman sequence analysis of the isolated protein and its tryptic peptides showed that the amyloid protein was derived from an immunoglobulin lambdaII-light chain. To our knowledge, this is the first reported case to isolate and chemically characterize amyloid fibrils from a localized rectal amyloidoma. The development of specific therapies for patients with amyloid-associated disorders emphasizes the need to characterize the biochemical nature of the amyloid fibril protein.