False negative biceps tendon sampling for detection of systemic amyloidosis: a case report

Amyloidosis is a group of disorders which have in common a pathologic process characterized by the extracellular deposition of insoluble protein aggregates in peripheral tissues and organs [9, 14]. There are many types of amyloidosis, and the most common types include AL (amyloid light-chain fragment), AA (amyloid A protein) and ATTR (transthyretin amyloidosis) [1, 2]. Additionally, ATTR may occur as a wild-type (wtATTR) protein that is associated with aging, or as hereditary (hATTR) mutation associated with familial inheritance [1, 2].