Amyloidosis secondary to xanthogranulomatous pyelonephritis: a case report and review of the literature

Xanthogranulomatous pyelonephritis (XGP) is a rare entity characterized by the formation of inflammatory renal masses rich in macrophages loaded with lipids. It is usually secondary to repeated urinary infections and urinary obstruction due to stones, which produce slow destruction of the renal parenchyma, requiring nephrectomy. It may sometimes be associated to secondary amyloidosis that leads to the appearance of a nephrotic syndrome. We have conducted a search in the Medline database between the years 1967 and 2003 and we only found 6 cases in adults and 3 cases in pediatric patients with amyloidosis secondary to xanthogranulomatous pyelonephritis. During this same period, there are more than 570 citations that include more than 1,000 patients with isolated XGP, so that we estimate that amyloidosis that complicates a XGP should be less than 1% of all the XGP cases. We present a case of XGP in a 51 year old female patient associated to amyloidosis that initiated with nephrotic syndrome, analyzing the clinical characteristics of the 9 previous cases. We compared their clinical characteristics with those of 51 patients with xanthogranulomatous pyelonephritis without amyloidosis of a large classical series in order to characterize this clinical picture better.