Pathophysiology and treatment of systemic amyloidosis.

Amyloid is an abnormal extracellular fibrillar protein deposit in the tissues. In humans, more than 25 different proteins can adopt a fibrillar conformation in vivo that results in the pathognomonic tinctorial property of amyloid (that is, green birefringence when an affected tissue specimen is stained with Congo red dye and viewed by microscopy under cross-polarized light). Amyloid deposition is associated with disturbance of organ function and causes a wide variety of clinical syndromes that are classified according to the respective fibril protein precursor. Systemic amyloidosis, in which amyloid deposits are widespread and typically accumulate gradually, continues to be fatal and is responsible for about one in 1,500 deaths per year in the UK. Advances in our understanding of the pathogenesis of systemic amyloidosis have resulted in the identification of new therapeutic targets, and several drugs with novel mechanisms of action are currently under development. Meanwhile, an increased awareness of amyloidosis coupled with enhancements to existing diagnostic techniques and therapeutic strategies have already resulted in better outcomes for patients with the disease.