Secondary amyloidosis from long-standing bacterial endocarditis

Infections and AA amyloidosis: An overview

BACKGROUND

Amyloidoses are a heterogeneous group of systemic diseases characterised by extracellular accumulation of insoluble amyloid fibrils derived from unfolded proteins. Inflammatory (AA) amyloidosis can complicate various inflammatory disorders that are associated with a sustained acute phase response and serum amyloid A (SAA) protein overproduction. Chronic infections were the first recognised cause of amyloidoses. However, with the better management of underlying diseases, the frequency of AA amyloidosis is decreasing.

PURPOSE

The aim of this overview was to discuss the several infections associated with AA amyloidosis and the relative frequency of infections as aetiological factors.

METHODS

A search of the literature was performed using the PubMed database using the MeSH terms "Amyloidosis" and "Infections," from inception to December 31st, 2019. Articles written in other languages than English or French were excluded.

RESULTS

The frequency of AA amyloidosis secondary to infections decreased from more than 50% to less than 20% after the 2000s, with a parallel increase in the frequency of AA amyloidosis secondary to inflammatory diseases and to an unknown cause.

CONCLUSION

Whereas new antibiotics have been developed and sanitary conditions are better, infections still represent 5%-30% of the causes of AA amyloidosis, including in developed countries. These data argue for better screening of chronic infections to prevent AA amyloidosis and the development of new strategies to manage recurrent infections.

Lactobacillus Endocarditis-Associated Glomerulonephritis Complicated by anti-Coagulant Nephropathy and Renal Amyloidosis

Kidney injury is a well-known sequelae of infectious endocarditis. Various types of kidney injury can be seen, including endocarditis-associated glomerulonephritis, and may affect nearly half of the patients with infectious endocarditis. Lactobacillus species are an infrequently documented cause of endocarditis. We present a case of Lactobacillus endocarditis-associated glomerulonephritis in a patient with a complex medical history including Lactobacillus infection of an artificial heart valve. To our knowledge, this is the first reported case of development of endocarditis-associated glomerulonephritis secondary to Lactobacillus species organisms. Furthermore, the patient's renal biopsy revealed several frequently overlooked concomitant findings including anti-coagulant nephropathy and renal amyloidosis.

Synchrotron x-ray microdiffraction reveals intrinsic structural features of amyloid deposits in situ

Amyloidoses are increasingly recognized as a major public health concern in Western countries. All amyloidoses share common morphological, structural, and tinctorial properties. These consist of staining by specific dyes, a fibrillar aspect in electron microscopy and a typical cross-β folding in x-ray diffraction patterns. Most studies that aim at deciphering the amyloid structure rely on fibers generated in vitro or extracted from tissues using protocols that may modify their intrinsic structure. Therefore, the fine details of the in situ architecture of the deposits remain unknown. Here, we present to our knowledge the first data obtained on ex vivo human renal tissue sections using x-ray microdiffraction. The typical cross-β features from fixed paraffin-embedded samples are similar to those formed in vitro or extracted from tissues. Moreover, the fiber orientation maps obtained across glomerular sections reveal an intrinsic texture that is correlated with the glomerulus morphology. These results are of the highest importance to understanding the formation of amyloid deposits and are thus expected to trigger new incentives for tissue investigation. Moreover, the access to intrinsic structural parameters such as fiber size and orientation using synchrotron x-ray microdiffraction, could provide valuable information concerning in situ mechanisms and deposit formation with potential benefits for diagnostic and therapeutic purposes.

Quantitative analysis of interstitial mast cells in AA and AL renal amyloidosis

Eighteen renal biopsy specimens obtained from patients with AA-type renal amyloidosis (AA) and 11 from patients with AL-type renal amyloidosis (AL), for whom both light and electron microscopy as well as immunofluorescence microscopy and full clinical data were available, were examined quantitatively. The cases were selected on the basis of immunohistochemical studies. As a control, we used 10 biopsy specimens from the kidneys removed because of trauma. Morphometric investigations were carried out by a computer image analysis system to find an answer to the question of whether mast cells can correlate with tubulointerstitial fibrosis in AA and AL renal amyloidosis, and to examine the relationship between mast cells and interstitial alpha-smooth muscle actin (alpha-SMA) expression and interstitial infiltrates. The morphometric study revealed that the mean values of the interstitial tryptase-positive cells, expression of alpha-SMA, interstitial volume, CD68+, CD45RB+, CD43+ and CD20+ cells were increased in AA as compared with the AL group, most of them significantly. Most of these parameters were also significantly increased in both AA and AL patients as compared with the control group. In both the AA group and the AL group, there existed some significant positive correlations between interstitial tryptase-positive cells and interstitial expression of alpha-SMA, interstitial volume and CD68+ cells. Interestingly, in AA cases, but not in AL cases, we noted a significant relationship between interstitial tryptase-positive cells and CD43+ cells. Our findings demonstrate that mast cells belong to the constitutive cell types in the interstitium in renal amyloidosis, in particular in amyloid type A. In addition, in both the AA group and the AL group, the significant positive correlations between interstitial mast cell count and relative interstitial volume and interstitial expression of alpha-SMA suggest that these cells play a role in the development of interstitial fibrosis.

Immunohistochemical characterization of amyloid fibril precursors in renal tissue

Amyloidosis is a heterogeneous group of disorders characterised by extracellular deposition of abnormal protein fibrils which are derived from different proteins in different forms of the disease. Almost all patients with amyloidosis have renal disorders. Distinguishing type of amyloidosis is important for therapeutic and investigative purposes. The different types of amyloid fibril proteins can be evaluated by immunohistochemistry, but not by routine histochemical techniques. On the basis of immunohistochemical studies two groups of amyloidosis were distinguished. In all cases, whatever the type, P component was detected, while none of the biopsies revealed transthyretin. The immunoperoxidase technique has the advantage of being able to detect amyloid in formalin-fixed paraffin embedded tissues and remains the simplest and very specific method for identifying amyloid fibril proteins.