AA amyloidosis: basic knowledge, unmet needs and future treatments

Systemic AA amyloidosis is a long-term complication of several chronic inflammatory disorders, including rheumatoid arthritis, ankylosing spondylitis, autoinflammatory syndromes, Crohn's disease, malignancies and conditions predisposing to recurrent infections. Organ damage results from the extracellular deposition of proteolytic fragments of the acute-phase reactant serum amyloid A (SAA) as amyloid fibrils. A sustained high concentration of SAA is the prerequisite for developing AA amyloidosis. However, only a minority of patients with long-standing inflammation actually presents with this complication, pointing to the existence of disease-modifying factors, the best characterised of which being SAA1 genotype. The kidneys, liver and spleen are the main target organs of AA amyloid deposits. In more than 90% of patients proteinuria, nephrotic syndrome and/or renal dysfunction dominate the clinical picture at onset. If not effectively treated, this disease invariably leads to end stage kidney disease and renal replacement therapy, that are still associated with a poor outcome. Although the incidence of AA in rheumatoid arthritis and other chronic arthritides has continuously decreased over the past ten years, thanks to the increasing availability of more effective anti-inflammatory and immunosuppressive therapies, AA remains a life-threatening disease with several areas of uncertainty and unmet needs, deserving continuous efforts at prevention and effective treatment. The deeper understanding of the molecular mechanisms of amyloid formation and regression is now driving the development of novel treatments targeting different steps in the amyloidogenic cascade. These therapies will hopefully improve the quality of life and outcome of these patients in a near future.