The long-term prognosis of AA and AL renal amyloidosis and the pathogenesis of chronic renal failure in renal amyloidosis

A rare presentation of kidney failure in a patient with giant cell arteritis: case report and review of literature

Although giant cell arteritis, also called temporal arteritis, is the most common primary vasculitis in the elderly, an association with AA amyloidosis has rarely been reported. AA amyloidosis is a disorder that results from the extracellular deposition of proteolytic cleavage products of serum amyloid A, which occurs in the setting of long-standing inflammation. We present a case of a patient with giant cell arteritis who developed a rapidly deteriorating kidney function, due to AA amyloidosis. Early recognition of this rare phenomenon is crucial as prompt treatment may be beneficial in the salvage of renal function.

Using digital whole-slide images to evaluate renal amyloid deposition and its association with clinical features and outcomes of AL amyloidosis

BACKGROUND

Few data are available quantifying the proportion of amyloid deposition in renal biopsy specimens. The aim of the study is to investigate the correlation between the proportion of amyloid deposition in renal biopsy and clinical characteristics of Chinese patients with immunoglobulin light-chain amyloidosis (AL amyloidosis).

METHODS

259 patients diagnosed with renal AL amyloidosis between 2003 and 2015 were studied retrospectively. We developed a digital, automated quantification method to evaluate amyloid deposits in glomeruli, vessels and interstitium on digital whole-slide images (WSIs). The associations between the proportion of amyloid-positive area in the renal biopsy and clinical manifestations were analyzed.

RESULTS

The proportion (%) of amyloid-positive area in glomeruli, vessels, interstitium and the whole renal tissue were 11.81 ± 11.38, 14.14 ± 14.05, 3.34 ± 5.36 and 4.25 ± 5.77, respectively. The proportion of amyloid deposition in glomeruli, vessels and interstitium was positively correlated with serum creatinine (Scr), estimated glomerular filtration rate (eGFR) and urinary retinol binding protein (RBP). The proportion of glomerular amyloid deposition, age, urinary N-acetyl-b-D-glucosaminidase (NAG) and urinary RBP could independently predict the risk for overall death. The proportion (%) of amyloid-positive area in blood vessels, interstitium and the whole renal tissue, Scr, and urinary RBP were independent risk factors associated with renal survival.

CONCLUSION

A novel digital analysis algorithm was firstly developed to quantify the proportion of amyloid deposits in renal tissues based on digital WSIs. The degree and localization of amyloid deposits in the kidney evaluated by digital WSIs may have predictive value in assessing risk of outcome of AL amyloidosis.

Correlation between amyloid deposits affecting renal compartments and glomerular filtration rate during renal biopsy in a renal amyloidosis case series

Amyloidosis comprises a group of disorders that accumulate modified autologous proteins in organs, mainly the kidneys. Few studies have addressed the amyloid compartmental distribution and associated clinical outcomes. The aim of this study was to present a case series of renal amyloidosis correlating histopathological data with glomerular filtration rate (GFR) during kidney biopsy. We studied 53 cases reviewed by nephropathologists from 2000 to 2018 in a single kidney biopsy center in Brazil. GFR was estimated using the CKD-EPI formula. Cases were divided into Group A ≥60 and Group B <60 mL·min⁻¹·(1.73 m²)⁻¹ using the estimated GFR during kidney biopsy. Semiquantitative histopathological study was performed, including extension and distribution of amyloid deposits by compartments (glomeruli, tubulointerstitial tissue, and vessels). Statistical analyses were made to understand associations with lower GFR. No difference was seen for age, gender, proteinuria, hematuria, subtype of amyloid protein, arteriosclerosis, interstitial fibrosis/infiltrate, or glomerular and interstitial amyloid deposits. After a previous P value <0.1 in the descriptive analysis, the following variables were selected: globally sclerotic glomeruli, high blood pressure, and the extension of vascular amyloid deposition. A binary logistic regression model with GFR as the dependent variable showed history of hypertension and vascular amyloid to be robust and independent predictors of Group B <60 mL·min⁻¹·(1.73 m²)⁻¹. Beyond the histopathologic diagnosis of amyloidosis, a semiquantitative approach on renal biopsy could provide new insights. Vascular amyloid is an independent predictor of renal dysfunction in cases of renal amyloidosis.

Renal amyloidosis: validation of a proposed histological scoring system in an independent cohort

Background

In systemic amyloidosis, the kidney is frequently affected and renal involvement has a major impact on survival. Renal involvement is clinically characterized by decreased estimated glomerular filtration rate (eGFR) and proteinuria. The two most common renal amyloidosis types are light chain-related amyloidosis (AL) and serum amyloid A (AA) amyloidosis. Standardized histopathological scoring of amyloid deposits is crucial to assess disease progression. Therefore, we aimed to validate the proposed scoring system from Rubinstein et al. (Novel pathologic scoring tools predict end-stage kidney disease in light chain (AL) amyloidosis. Amyloid 2017; 24: 205–211) in an independent patient cohort.

Methods

We attempt to reproduce the scoring system, consisting of an amyloid score (AS) and a composite scarring injury score (CSIS), in a multicentre AL and AA case series. Additionally, we analysed all renal amyloidosis kidney biopsies performed in the Netherlands between 1993 and 2012.

Results

Similar to the original study, AS and CSIS correlated to eGFR (r = −0.45, P = 0.0061 and r = −0.60, P < 0.0001, respectively) but not to proteinuria at diagnosis. Furthermore, AS, but not CSIS, was associated with renal outcome. The scoring system was not reproducible in AA patients. The median incidence rate for renal amyloidosis in the Netherlands was 2.3 per million population per year, and increased during the study period.

Conclusions

In our AL case series and the original study, AS and CSIS were correlated to eGFR but not to proteinuria, and AS correlated with renal outcome. Overall, we regard this scoring system as competent for standardized histopathological assessment of amyloid deposits burden and thereby disease advancement in renal biopsies.

Renal involvement in AA amyloidosis: clinical outcomes and survival

BACKGROUND

The natural history of AA amyloidosis is typically progressive, leading to multiple organ failure and death. We analyzed the etiology as well as clinical and laboratory features of patients with biopsy-proven AA amyloidosis and evaluated the ultimate outcome.

METHODS

Seventy-three patients (24 female; mean age 41.85±15.89 years) were analyzed retrospectively. Demographic, clinical and laboratory features were studied and the outcome was assessed.

RESULTS

Familial Mediterranean Fever and tuberculosis were the most frequent causes of amyloidosis. Mean serum creatinine and proteinuria at diagnosis were 4.65±4.89 mg/dl and 8.04±6.09 g/day, respectively; and stage I, II, III, IV and V renal disease were present in 19.2%, 13.7%, 16.4%, 11%, and 39.7% of the patients, respectively. ESRD developed in 16 patients during the follow-up period. All of the ESRD patients started a dialysis programme. Thirty patients (41%) died during the follow-up period; median patient survival was 35.9±6.12 months. Old age, tuberculosis etiology, advanced renal disease and low serum albumin levels were associated with a worse prognosis. Serum albumin was a predictor of mortality in logistic regression analysis.

CONCLUSION

The ultimate outcome of the patients with AA amyloidosis is poor, possibly due to the late referral to the nephrology clinics. Early referral may be helpful to improve prognosis.

Significant association between renal function and amyloid-positive area in renal biopsy specimens in AL amyloidosis

Background

The kidney is a major target organ for systemic amyloidosis that often affects the kidney including proteinura, and elevated serum creatinine (Cr). The correlation between amount of amyloid deposits and clinical parameters is not known. The aim of this study was to clarify correlation the amyloid area in all renal biopsy specimen and clinical parameters.

Methods

Fifty-eight patients with an established diagnosis of AL amyloidosis participated in the study. All patients showed amyloid deposits in renal biopsies. We retrospectively investigated the correlation between clinical data and amyloid occupied area in whole renal biopsy specimens.

Results

The area occupied by amyloid was less than 10% in 57 of the 58 patients, and was under 2% in 40. For statistical analyses, %amyloid-positive areas were transformed to common logarithmic values (Log₁₀%amyloid). Cr showed significant correlation with Log₁₀%amyloid and estimated glomerular filtration rate (eGFR) showed the significant negative correlation. Patient age, cleatinine clearance (Ccr), blood urea nitorogen, and urinary protein was not significantly correlated with Log₁₀%amyloid. The correlation with other clinical factors such as sex, and serum concentrations of total protein, albumin, immunoglobulins, compliments was evaluated. None of these factors significantly correlated with Log₁₀%amyloid. According to sex- and age- adjusted multiple linear regression analysis, Log₁₀%amyloid had significant positive association with Cr and significant negative association with eGFR.

Conclusion

There is significant association between amyloid-positive area in renal tissue and renal function, especially Cr and eGFR. The level of Cr and eGFR may be a marker of amount of amyloid in renal tissue.

Renal amyloidosis in children

Renal amyloidosis is a detrimental disease caused by the deposition of amyloid fibrils. A child with renal amyloidosis may present with proteinuria or nephrotic syndrome. Chronic renal failure may follow. Amyloid fibrils may deposit in other organs as well. The diagnosis is through the typical appearance on histopathology. Although chronic infections and chronic inflammatory diseases used to be the causes of secondary amyloidosis in children, the most frequent cause is now autoinflammatory diseases. Among this group of diseases, the most frequent one throughout the world is familial Mediterranean fever (FMF). FMF is typically characterized by attacks of clinical inflammation in the form of fever and serositis and high acute-phase reactants. Persisting inflammation in inadequately treated disease is associated with the development of secondary amyloidosis. The main treatment is colchicine. A number of other monogenic autoinflammatory diseases have also been identified. Among them cryopyrin-associated periodic syndrome (CAPS) is outstanding with its clinical features and the predilection to develop secondary amyloidosis in untreated cases. The treatment of secondary amyloidosis mainly depends on the treatment of the disease. However, a number of new treatments for amyloid per se are in the pipeline.

A long-term remission of renal amyloidosis with nephrotic syndrome after autologous peripheral blood stem-cell transplantation

Renal amyloidosis is typically characterized by nephrotic syndrome, often with massive proteinuria and refractory peripheral edema. We report the case of a patient with renal amyloidosis associated with nephrotic syndrome who maintained remission for 6 years after undergoing high-dose chemotherapy followed by autologous peripheral blood stem-cell transplantation (auto-PBSCT). The patient was a man aged in his 50s who had developed nephrotic syndrome. Bone marrow aspiration and kidney biopsy determined that the cause of the nephrotic syndrome was renal amyloidosis due to multiple myeloma, and the patient was admitted to our department in July 2003. After one course of chemotherapy, auto-PBSCT was performed in March 2004. Following transplantation, serum M-protein was no longer detectable from March 2005, and the patient achieved complete hematological remission. Subsequently, proteinuria decreased, serum albumin levels normalized, and nephrotic syndrome improved. As of 6 years after transplantation, in March 2010, the patient remained in remission, meaning that auto-PBSCT proved extremely effective as a treatment for renal amyloidosis in this case.

Renal amyloidosis revisited: amyloid distribution, dynamics and biochemical type

BACKGROUND

Renal amyloidosis results from protein misfolding and leads to progressive renal insufficiency. Few data are available concerning the relevance of the histomorphological patterns and the dynamics of the disease process.

METHODS

Cases of renal amyloidosis in native kidney biopsies (n = 203) were retrospectively evaluated for the pattern of amyloid distribution, the extent of glomerular amyloid deposition and the amount of interstitial fibrosis and tubular atrophy. One hundred and fifty-eight cases were characterized by immunohistochemistry to determine the biochemical amyloid type. Morphological findings were correlated with available clinical data.

RESULTS

According to the predominant site of amyloid deposition, 84.6% showed a glomerular, 9.4% a vascular and 6% a tubulointerstitial distribution pattern. Within the glomeruli, amyloid was initially deposited in a focal segmental fashion that became diffuse and global in later stages. Most cases were identified as AL lambda (84/158) or AA (68/158). There was no correlation between the biochemical type and the distribution pattern. Serum creatinine correlated well with interstitial fibrosis and tubular atrophy and proteinuria with the glomerular amyloid load.

CONCLUSIONS

The relevance of the different distribution patterns is unclear at the moment, but they may be due to the physicochemical properties of the amyloid fibrils in a given patient. This may become important in future anti-fibrillar therapies.

Is the urinary protein excretion pattern compatible with renal morphological findings in renal amyloidosis?

The aims of this study are to compare urinary protein excretion pattern with renal morphological findings and to find out whether urinary protein excretion pattern is a prognostic indicator of renal amyloidosis. Fifteen children with renal amyloidosis secondary to familial Mediterranean fever were included in the study. The patients were classified into three groups according to the degree of tubulointerstitial injury in renal biopsy (group 1, <25%; group 2, 25-50%; and group 3, >50%). In all patients, urinary protein electrophoresis were performed. Levels of urinary beta(2)-microglobulin, retinol binding protein, and beta.N-acetyl-D glucosaminidase were measured as markers for tubular injury, and urinary excretions of protein and albumin and plasma albumin levels were measured as markers of glomerular injury. While urinary excretions of protein and albumin and plasma albumin levels were not different between groups, higher urinary beta(2-)microglobulin and retinol binding protein values and lower creatinine clearance values were found in group 3 than in groups 1 and 2 (p < 0.05). We concluded that analysis of urinary protein excretion pattern is a non-invasive and reliable method to detect the degree of tubulointerstitial injury as the most important prognostic factor in renal amyloidosis and may be used to determine the changes during the follow-up period of the patients.

Gene expression profiling in the remnant kidney model of wild type and kinin B1 and B2 receptor knockout mice

Angiotensin-converting enzyme inhibitors are the most efficient pharmacologic agents to delay the development of end-stage renal disease (ESRD). This is a multipharmacologic approach that inhibits angiotensin II formation while increasing kinin concentrations. Considerable attention has been focused on the role of decreased angiotensin II levels; however, the role of increased kinin levels is gaining in interest. Kinins affect cellular physiology by interacting with one of two receptors being the more inducible B1 and the more constitutive B2 receptors. This study utilizes the mouse remnant kidney of 20 weeks duration as a model of ESRD. Whole mouse genome microarrays were used to evaluate gene expression in the remnant kidneys of wild type, B1 and B2 receptor knockout animals. The microarray data indicate that gene families involved in vascular damage, inflammation, fibrosis, and proteinuria were upregulated, whereas gene families involved in cell growth, metabolism, lipid, and protein biosynthesis were downregulated in the remnant kidneys. Interestingly, the microarray analyses coupled to histological evaluations are suggestive of a possible protective role of kinins operating through the B2 receptor subtype in this model of renal disease. The results highlight the potential of microarray technology for unraveling complex mechanisms contributing to chronic renal failure.

Diagnostic performance of amyloid A protein quantification in fat tissue of patients with clinical AA amyloidosis

OBJECTIVE

Amyloid A protein quantification in fat tissue is a new immunochemical method for detecting AA amyloidosis, a rare but serious disease. The objective was to assess diagnostic performance in clinical AA amyloidosis.

METHODS

Abdominal subcutaneous fat tissue of patients with AA amyloidosis was studied at the start of an international clinical trial with eprodisate (NC-503; 1,3-propanedisulfonate; Kiacta), an antiamyloid compound. All patients had renal findings, i.e. proteinuria (> or =1 g/day) or reduced creatinine clearance (20 - 60 ml/min). Controls were patients with other types of amyloidosis and arthritic patients without amyloidosis. Amyloid A protein was quantified by ELISA using monoclonal antihuman serum amyloid A antibodies. Congo red stained slides were scored by light microscopy in a semiquantitative way (0 to 4+).

RESULTS

Ample fat tissue (>50 mg) was available for analysis in 154 of 183 patients with AA amyloidosis and in 354 controls. The sensitivity of amyloid A protein quantification for detection of AA amyloidosis (>11.6 ng/mg fat tissue) was 84% (95% CI: 77 - 89%) and specificity 99% (95% CI: 98 - 100%). Amyloid A protein quantification and semiquantitative Congo red scoring were concordant. Men had lower amyloid A protein values than women (p < 0.0001) and patients with familial Mediterranean fever had lower values than patients with arthritis (p < 0.001) or other inflammatory diseases (p < 0.01).

CONCLUSIONS

Amyloid A protein quantification in fat tissue is a sensitive and specific method for detection of clinical AA amyloidosis. Advantages are independence from staining quality and observer experience, direct confirmation of amyloid AA type, and potential for quantitative monitoring of tissue amyloid over time.

Prognostic factors for renal amyloidosis: a clinicopathological study using cluster analysis

OBJECTIVE

There is no standardized therapy for renal amyloidosis, which shows rapid progression and poor prognosis. Here, we used cluster analysis to examine the correlation between amyloid-related renal damage and prognosis, and determined the clinicopathological prognostic factors for renal amyloidosis.

METHODS AND PATIENTS

We analyzed 125 patients with renal amyloidosis (men/women: 43/82; mean age at renal biopsy: 58.8+/-11.1 years, +/-SD; range: 21-78 years). Cluster analysis was performed using clinical parameters, renal histological findings, type of renal amyloidosis, and follow-up data. We also analyzed survival data.

RESULTS

We divided 125 cases (prognosis was checked in 97 [77.6%] cases) into three groups by cluster analysis. In the cluster groups, accelerated progression correlated with serum creatinine (s-Cr) levels at renal biopsy and histological grade of renal damage by amyloid deposition (p<0.0001). The most important prognostic factors were glomerular, tubulointerstitial, and vascular lesions induced by amyloid deposition at biopsy (p<0.0001). We also found that amyloid-A (AA) type amyloidosis correlated is more significantly with amyloid-mediated vascular (P=0.0010) and tubulointerstitial lesions (p=0.0705) than with amyloid-L (AL) type amyloidosis. Proteinuria and nephrotic syndrome were more severe in AL than AA amyloidosis (p=0.0836). The 10-year individual survival rate was about 20%, and most deaths were due to cardiovascular disease and infection.

CONCLUSION

Our results indicate that the quantity of amyloid deposition in the kidney, and the extent of glomerular, tubulointerstitial, and vascular damage are significant renal prognostic factors in amyloidosis.

Amyloses multisystémiques

OBJECTIVE

Clinical analysis of multisystem amyloidosis in Lebanon, by histological type.

METHOD

Retrospective study of 39 cases of multisystem amyloidosis diagnosed histologically in a university hospital center between 1991 and 2002. It analyzed the following clinical data: age, gender, type of presentation, time from symptom onset to diagnosis, clinical features, concomitant diseases, family history of amyloidosis, biopsy sites, presence of urinary or serum monoclonal gammopathy, immunohistochemical type, prognosis and treatment.

RESULTS

Median age at diagnosis was 56+/-18 years. The overall ratio of men to woman was 1.4. AL amyloidosis (amyloid light chain) accounted for 54% (21/39) of the cases, AA (amyloid-associated) amyloidosis 36% (14/39), while 10% (4/39) were not typed. Among the 21 cases of AL amyloidosis, 12 were idiopathic (57%) and 9 (43%) were associated with multiple myeloma; among the 14 cases of AA amyloidosis, 7 were associated with familial Mediterranean fever and 5 with chronic disorders. Proteinuria was often the first symptom. The initial manifestations in AL amyloidosis patients with myeloma were more often related to amyloidosis than to myeloma. Renal involvement was seen in 95% (37/39) of all cases (95% of AL versus 93% of AA), proteinuria in 87% of cases and renal failure in 72%. Cardiac amyloidosis (57% of AL versus 7% of AA; p>0.05), infiltration of the tongue (19% of AL versus 0% of AA; p>0.05) and neurological manifestations (24% of AL versus 7% of AA; p>0.05) were more frequent in AL amyloidosis. The 7 patients who died (18%) had AL amyloidosis (5 of them had myeloma). Heart failure was the most frequent cause of death related to amyloid.

CONCLUSION

Multisystem amyloidosis is frequent in Lebanon and familial Mediterranean fever is still frequently associated with the secondary type. Accurate diagnosis and classification are essential for the prognosis and treatment of the disease. Poor prognosis was associated with the AL type, especially when accompanied by myeloma, and with cardiac amyloidosis.

Efficacy of colchicine therapy in amyloid nephropathy of familial Mediterranean fever

The aim of this study was to investigate the effect of colchicine therapy on the outcome of amyloid nephropathy of familial Mediterranean fever (FMF) in childhood. The diagnosis of amyloidosis type AA was confirmed by renal biopsy in 38 patients. During a mean follow-up period of 30.5 months (range 6-88 months), the patients received colchicine therapy. While 24 of these patients were compliant with the treatment, 14 patients remained non-compliant. Of the 24 compliant patients, 19 had normal renal function at the onset; in 13 the proteinuria improved, in 5 patients it remained stable, and in 1 patient it deteriorated from a proteinuric to nephrotic stage. Partial resolution of amyloidosis was demonstrated by repeat renal biopsy in 1 patient who showed complete resolution of proteinuria. In contrast, none of 14 non-compliant patients improved, and while only 1 patient was in renal failure initially, 10 patients deteriorated to renal failure during the follow-up period. The presence of tubulointerstitial injury at presentation adversely affected the prognosis. In conclusion, when used appropriately, colchicine can improve proteinuria and prevent chronic renal failure in patients with amyloid nephropathy of FMF. The presence of renal failure or tubulointerstitial injury at presentation and non-compliance with therapy are the factors decreasing the success of therapy.

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.

Increased density of interstitial mast cells in amyloid A renal amyloidosis

Renal interstitial fibrosis is the final common pathway leading to end-stage renal disease in various nephropathies including renal amyloidosis. However, the role of mast cells (MCs) in the fibrotic process of renal amyloidosis is not fully understood. We compared the distribution of MCs in renal biopsies from 30 patients with AA type renal amyloidosis and 20 control cases. Immunoreactivity of renal MCs to anti-tryptase and anti-chymase was studied. Interstitial myofibroblasts were stained with anti-alpha-smooth muscle actin (alpha-SMA) antibody, and inflammatory cells were identified by anti-CD45, -CD20, and -CD68 mAbs. Positively stained cells were counted, and the relative interstitial and fractional areas of anti-alpha-SMA stained cells were measured. Anti-CD29 mAb was used to detect beta1 integrin and anti-basic fibroblast growth factor (bFGF) mAb for the growth factor on MCs. MCs were rarely found in control samples. In contrast, samples showing amyloid deposition contained numerous tryptase-positive (MCT) (940.17 +/- 5.4 versus 6.74 +/- 1.1/mm2) but fewer chymase-positive (MCTC) cells (20.7 +/- 2.86 versus 1.7 +/- 0.76/mm2) in the renal interstitium. There was a significant relationship between interstitial MCT and creatinine clearance (r = -0.72), and between interstitial MCT and glomerular amyloid-index (GAI) (r = 0.723) and interstitial amyloid area (r = 0.824). Accumulation of MCs correlated significantly with the number of T lymphocytes (MCT: r = 0.694). There was also a significant relationship between mast cell (MC) number and the fractional area of alpha-SMA positive interstitium (r = 0.733) and interstitial fibrotic area (r = 0.6). Double immunostaining demonstrated intracytoplasmic presence of beta1 integrin on 87% of MCT and correlated significantly with the interstitial amyloid area (r = 0.818, P = .001) and T-cell number (r = 0.639, P = .002). bFGF was also detected on 85.5% of MCTC correlating well with the interstitial alpha-SMA-area (r = 0.789). Our results indicate that MCs constitute an integral part of the overall inflammatory process and play a crucial role in interstitial fibrosis in renal amyloidosis.

Amyloid precursors and amyloidosis in rheumatoid arthritis

Amyloidosis refers to the extracellular accumulation of amyloid fibrils, derived from a circulating precursor, in various tissue and organs. The most common form of amyloidosis worldwide is that which occurs secondary to chronic inflammatory disease, particularly rheumatoid arthritis. The precursor molecule is serum amyloid A (SAA), an acute phase reactant, which can be used as a surrogate marker of inflammation in many diseases. SAA has a number of immunomodulatory roles, can induce chemotaxis and adhesion molecule expression, has cytokine-like properties and can promote the upregulation of metalloproteinases. It enhances the binding of high density lipoprotein to macrophages and thus helps in the delivery of lipids to sites of injury for use in tissue repair. It is thus thought to be an integral part of the disease process. Moreover, elevated levels of SAA over time predispose to secondary amyloidosis. Pathogenic factors underlying this disease are outlined along with guidelines for diagnosis and management.

The classification of amyloid deposits in clinicopathological practice

A series of 104 biopsy cases with histopathological proof of amyloid, submitted to our department of pathology over the last 19 years, were re-examined. The survey investigated the medical indication for surgery, the origin and quality of the biopsy and the clinical information as documented on the request form for histopathological examination and in hospital records. Amyloid deposits were classified using antisera directed against five major amyloid fibril proteins, i.e. AA, ATTR, A lambda, A kappa and A beta 2M and optimal conditions were sought for the reliable and early characterization of amyloid disease in clinicopathological practice. This survey revealed that 98% of the biopsy cases already suffered from a disease which was either a cause or a result of amyloidosis. In only 2% of the biopsy cases was amyloidosis detected without any clinical indication. Immunohistochemical classification of the amyloid deposits and comparison with hospital records demonstrated diagnostic pitfalls such as immunostaining of amyloid by two or more antibodies recognizing different fibril proteins, and disagreement between immunohistochemical typing of amyloid and the initial clinical diagnosis. Based on these observations we assume that the characterization of amyloid disease and its biological significance is impossible in clinicopathological practice without clinical information or without immunohistochemical classification of the fibril protein in biopsy specimens. Different aspects of histopathological detection of AA- and AL-amyloidosis are discussed.

Significance of increased accumulation of type VI collagen and transforming growth factor beta 1 in tubulointerstitial damage in hypertensive nephrosclerosis: an immunohistochemical study

The distribution of type VI collagen and transforming growth factor beta 1 (TGF beta 1) was studied by immunohistochemistry in 12 renal biopsy specimens of hypertensive nephrosclerosis and five control cases. In control kidneys, the immunostaining of type VI collagen was found in the mesangium, glomerular basement membrane and tubular basement membrane. For TGF beta 1, mesangium, glomerular basement membrane, tubular basement membrane and tubular epithelial cells stained positively in the control kidneys. In contrast to the control cases, markedly increased immunostaining for both type VI collagen and TGF beta 1 was consistently observed in tubulointerstitial damage in hypertensive nephrosclerosis. These immunohistochemical findings provide the evidence for a parallel increase of both type VI collagen and TGF beta 1 during the process of tubulointerstitial injury in hypertensive nephrosclerosis. From the results of the present study, it is speculated that TGF beta 1 may contribute to the tubulointerstitial injury by stimulating increased synthesis of various extracellular matrix including type VI collagen.

Clinical and therapeutic aspects of AA amyloidosis

Approach to the management of AA amyloidosis complicating RA. (A) In case of proteinuria or loss of renal function a rectal biopsy or a subcutaneous fat biopsy is a suitable screening method for the detection of amyloidosis. If in any doubt, try to ascertain the diagnosis by renal biopsy. Adequate staining with alkaline Congo red and preferably immunohistochemical staining with anti-AA antibodies should be performed. Beware of renal pathology other than amyloidosis even in the presence of a positive rectal biopsy. (B) A vigorous attempt to control disease activity of the RA should be made in order to eliminate the production of SAA, an acute phase protein. The response to treatment should be monitored by serial measurements of CRP and preferably SAA. (C) The function of some vital organs should be evaluated: (a) endogenous creatinine clearance and the extent of proteinuria; (b) electrocardiogram and optional echocardiography; (c) thyroid function and adrenocortical function; (d) intestinal absorption tests; (e) optional--SAP scintigraphy and turnover studies. (D) Attention should be given to adequate supportive treatment: (a) blood pressure control; (b) treatment of intercurrent infections; (c) corticosteroids during major surgical procedures; (d) pay attention to the possible effect of NSAID on proteinuria and renal function. (E) In case of total renal failure or uncontrollable proteinuria: (a) consider the possibility of primary renal transplantation; (b) otherwise regular haemodialysis is indicated.