One Illness Always Conceals Another: A Rare Case of Renal AA Amyloidosis Secondary to Progressive Systemic Sclerosis

Amyloidosis is a disparate group of diseases characterized by the extracellular deposition of abnormal proteins in diverse organs, leading to the progressive deterioration of one or several of them. There are several types of amyloidosis, but the three most frequently encountered are, in order of frequency, primary light chain (AL), secondary chain (AA), and wild-type transthyretin (ATTR), depending on the type of precursor protein found in the organs and whether or not another disease coexists. Secondary AA amyloidosis, which mainly affects the kidneys, may develop due to an underlying infection or long-term chronic inflammatory conditions. Additionally, chronic elevation of serum amyloid A (SAA) levels continues to be a significant risk factor for the development of AA amyloidosis in rheumatic diseases, and the prognosis can be unforeseeable. According to the literature, there are very few reported cases of AA amyloidosis secondary to progressive systemic sclerosis (PSS). Here we present a rare case of renal AA amyloidosis secondary to PSS and a literature review.