The term "
amyloidosis" encompasses the heterogeneous group of diseases caused by the extracellular deposition of autologous fibrillar
proteins. The global incidence of
amyloidosis is estimated at five to nine cases per million patient-years. While
amyloid light-chain (
AL) amyloidosis is more frequent in developed countries,
amyloid A (
AA) amyloidosis is more common in some European regions and in developing countries. The spectrum of
AA amyloidosis has changed in recent decades owing to: an increase in the median age at diagnosis; a percent increase in the frequency of primary
AL amyloidosis with respect to the AA type; and a substantial change in the epidemiology of the underlying diseases. Diagnosis of
amyloidosis is based on clinical organ involvement and histological evidence of
amyloid deposits. Among the many tinctorial characteristics of
amyloid deposits, avidity for
Congo red and metachromatic birefringence under unidirectional polarized light remain the gold standard. Once the initial diagnosis has been made, the
amyloid subtype must be identified and systemic organ involvement evaluated. In this sense, the (123)I-labeled
serum amyloid P component scintigraphy is a safe and noninvasive technique that has revolutionized the diagnosis and monitoring of treatment in systemic
amyloidosis. It can successfully identify anatomical patterns of
amyloid deposition throughout the body and enables not only an initial estimation of prognosis, but also the monitoring of the course of the disease and the response to treatment. Given the etiologic diversity of
AA amyloidosis, common therapeutic strategies are scarce. All treatment options should be based upon a greater control of the underlying disease, adequate organ support, and treatment of symptoms. Nevertheless, novel therapeutic strategies targeting the formation of
amyloid fibrils and
amyloid deposition may generate new expectations for patients with
AA amyloidosis.