Systemic amyloidosis occurs in two main variations: AL (primary amyloidosis, associated with the presence of a monoclonal variation of plasmacells) and AA (amyloidosis secondary to chronic inflammatory diseases). Some English researchers belonging to the National Amyloidosis Centre have described the natural history of the disease in 374 patients affected by AA and studied during a period of 15 years (the average age at diagnosis was 50 years old). The existing chronic inflammatory disease was represented in 60% of cases by osteoarthritis and in 15% of cases by infections. In basal conditions, 97% of patients had a renal involvement with proteinuria or with serum creatinine levels increase. Through a scintigraphy capable to reveal amyloid accumulations, 23% of patients presented an asymptomatic liver involvement; only one subject presented myocardial involvement while nobody had symptoms referring to autonomic neuropathy. During a follow-up of more than 7 years, scintigraphy has shown the decrease in amyloid accumulation in 12% of patients and its disappearance in 39% of them. Quite half of the patients died during that period and this mortality rate resulted directly proportional to blood levels of amyloid protein A and directly proportional to amyloid amounts revealed by scintigraphy. As it was expected, the progressive renal dysfunction was an important predictor of mortality rate increase.
This important trial confirmed that renal dysfunction represented the natural and most dreadful evolution of secondary amyloidosis. It must be underlined that, according to a recent trial (NEJM 2007; 356:2349), the experimental use of the drug eprodisate was capable to slow the progression of renal failure down in AA amyloidosis, but this was not translated into a survival increase.
