AL Amyloidosis with Renal Involvement

A 16-year Survey of Clinicopathological Findings, Electron Microscopy, and Classification of Renal Amyloidosis

Background

Electron microscopy (EM) is a valuable tool in the diagnosis of renal amyloidosis, particularly in the early stages of the disease. In Iran, studies on EM and the clinical features of renal amyloidosis are scarce. The objective of the present study was to survey EM investigations, pathological classifications, and clinical features of renal amyloidosis.

Methods

This cross-sectional study was performed in Shiraz, Iran, during 2001-2016. Out of 2,770 kidney biopsies, 27 cases with a diagnosis of renal amyloidosis were investigated. EM investigation and six staining procedures for light microscopy (LM) were performed. Two pathological classifications based on glomerular, peritubular, perivascular, and interstitial involvement were made. Finally, the association between these classifications and the clinical features was assessed. Chi-square, Fisher's exact, Independent t test, and Multiple logistic regression analysis were used. P values<0.05 were considered statistically significant.

Results

In 51.9% of the cases, the clinical diagnosis was nephrotic syndrome. Proteinuria and edema were the most prevalent clinical manifestations. The role of EM investigation for diagnosis was graded "necessary" or "supportive" in 48.2% of the patients. In the classification based on glomerular classes, variables such as the mean blood pressure (P=0.003), history of hypertension (P=0.02), creatinine >1.5 (P=0.03), and severe tubular atrophy (P=0.03) were significantly higher in class B (advanced amyloid depositions).

Conclusion

EM plays an important role in the diagnosis of renal amyloidosis. EM in conjunction with LM investigation with Congo red staining is recommended, to prevent misdiagnosis of patients with a clinical suspicion of renal amyloidosis. Among different pathological features of renal amyloidosis, the severity of glomerular amyloid depositions had a clear relationship with clinical presentations.

Clinicopathological features of renal amyloidosis: a single-center study on 47 cases

The correlations between the clinicopathological features and the long-term outcomes of renal amyloidosis (RA) were analyzed with a view to develop strategies for improving diagnosis and prognosis of RA. We retrospectively reviewed the clinicopathological characteristics of 47 patients diagnosed with RA between 2004 and 2014 at the Wuhan Union Hospital. The data on the renal histology, clinical manifestations, and prognosis of RA patients were retrieved from the hospital records and characteristic patterns were identified. The histological changes in the kidneys were correlated with the clinical manifestations of RA. Additionally, most RA patients in this study had decreased serum levels of κ light chain and increased urine levels of κ and λ light chains as well as presence of M-protein in the urine and serum. Patients with early RA showed no specific pathognomonic symptoms. Bleeding associated with diagnostic renal biopsy was rare. We recommend that the routine work-up of patients aged over 40 years and presenting with non-diabetic nephropathy includes the non-invasive tests for the measurement of serum and urine levels of κ and λ light chains as well as protein electrophoresis tests for the presence of urinary and serum M-protein. Additionally, such patients should undergo renal biopsy screening with Cong-red staining to ensure early diagnosis of RA and improve their survival, since the risk of hemorrhage related to renal biopsy screening is low at early stages of RA.

Binding with nucleic acids or glycosaminoglycans converts soluble protein oligomers to amyloid

Ample evidence suggests that almost all polypeptides can either adopt a native structure (folded or intrinsically disordered) or form misfolded amyloid fibrils. Soluble protein oligomers exist as an intermediate between these two states, and their cytotoxicity has been implicated in the pathology of multiple human diseases. However, the mechanism by which soluble protein oligomers develop into insoluble amyloid fibrils is not clear, and investigation of this important issue is hindered by the unavailability of stable protein oligomers. Here, we have obtained stabilized protein oligomers generated from common native proteins. These oligomers exert strong cytotoxicity and display a common conformational structure shared with known protein oligomers. They are soluble and remain stable in solution. Intriguingly, the stabilized protein oligomers interact preferentially with both nucleic acids and glycosaminoglycans (GAG), which facilitates their rapid conversion into insoluble amyloid. Concomitantly, binding with nucleic acids or GAG strongly diminished the cytotoxicity of the protein oligomers. EGCG, a small molecule that was previously shown to directly bind to protein oligomers, effectively inhibits the conversion to amyloid. These results indicate that stabilized oligomers of common proteins display characteristics similar to those of disease-associated protein oligomers and represent immediate precursors of less toxic amyloid fibrils. Amyloid conversion is potently expedited by certain physiological factors, such as nucleic acids and GAGs. These findings concur with reports of cofactor involvement with disease-associated amyloid and shed light on potential means to interfere with the pathogenic properties of misfolded proteins.

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.

Rapidly progressive glomerulonephritis complicating primary AL amyloidosis and multiple myeloma

Crescentic glomerulonephritis is a rare complication of AA amyloidosis. There are no clinical case reports of this complicating AL amyloidosis. A 67-year-old man developed rapidly progressive glomerulonephritis (RPGN) on a background of primary AL amyloidosis and IgGkappa multiple myeloma. Investigations for causes of glomerulonephritis were negative, and a renal biopsy confirmed crescentic glomerulonephritis and amyloid deposition. He progressed to end stage kidney disease (ESKD) requiring dialysis after 2 months and died 7 months after diagnosis after further treatment of multiple myeloma failed to arrest progression. We believe this to be the first clinical case report of RPGN complicating primary (AL) renal amyloidosis and multiple myeloma.