Slowly Progressive Male Alport Syndrome Evaluated by Serial Biopsy: Importance of Type IV Collagen Staining.

A slowly progressive middle-aged man initially diagnosed with thin basement membrane nephropathy based on extensive thinning of the glomerular basement membrane (GBM) was subsequently diagnosed with Alport syndrome (AS) by a serial renal biopsy eight years later. The ultrastructural analysis of the second biopsy indicated thickening and wrinkling with mild reticulation in the GBM, consistent with AS. However, a retrospective analysis of the first biopsy revealed mild attenuation of type IV collagen α5 chain staining, suggesting a potential diagnosis of AS, despite the lack of ultrastructural features of AS. We herein report the clinical usefulness of type IV collagen staining in the early diagnosis of AS.

Glomerular Basement Membrane Protein Expression and the Diagnosis and Prognosis of Autosomal Dominant Alport Syndrome.

Alport syndrome is a hereditary glomerular nephritis associated with hearing loss and eye abnormalities and is classified as X-linked Alport syndrome, autosomal recessive Alport syndrome, and autosomal dominant Alport syndrome. Autosomal dominant Alport syndrome is caused by a mutation in the gene encoding type IV collagen α3 (α3[IV]); (COL4A3), or α4 (α4[IV]); (COL4A4). Autosomal dominant Alport syndrome progresses more gradually than male X-linked Alport syndrome and autosomal recessive Alport syndrome. Differentiating autosomal dominant Alport syndrome from thin basement membrane nephropathy, which shows better kidney prognosis, remains challenging. Because autosomal dominant Alport syndrome is linked to a heterozygous mutation, type IV collagen is produced by the wild-type allele, and all α(IV) chains are supposed to be normally expressed. In this study, the pathologic findings of a patient with Alport syndrome with a novel COL4A4 heterozygous nonsense mutation were investigated. We observed weaker staining of α5(IV) in the glomerular basement membrane and enhanced expressions of α2(IV), laminin, and fibronectin, which were assumed to be caused by compensatory mechanisms for lack of enough α3α4α5(IV) expression in the glomerular basement membrane. These findings may be useful not only for differentially diagnosing autosomal dominant Alport syndrome from thin basement membrane nephropathy, but also for determining the extent of progression and predicting kidney prognosis.

Antineutrophil cytoplasmic antibody-associated glomerulonephritis with immunoglobulin deposition.

BACKGROUND: Antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis is commonly classified as pauci-immune glomerulonephritis; however, some cases have granular immunoglobulin deposition along the glomerular capillary. The pathogenesis of immune deposits is poorly studied. METHODS: Of 66 patients diagnosed with ANCA-associated glomerulonephritis on renal biopsy, cases with immunoglobulin deposition along the glomerular capillary were identified and their clinicopathological characteristics were analyzed. We also performed myeloperoxidase (MPO) and double immunofluorescence (IF) stainings to determine the presence of immune complex antigens. RESULTS: Granular IgG deposition, IgG plus IgM deposition, and IgM deposition were observed in 15 (22.1%), 8 (11.2%), and 17 (25.0%) cases, respectively. In cases with granular IgG deposition, MPO-IgG double IF staining revealed co-localization of MPO and IgG. In cases with granular IgM deposition, MPO-IgM double IF staining did not co-localize. By electron microscopy, subepithelial deposition as well as intramembranous, subendothelial, and mesangial deposition was detected in the patients with IgG deposition. In addition, renal survival curves were not significantly different between the immunoglobulin deposition and non-deposition groups. CONCLUSIONS: Granular IgG and/or IgM deposition was observed in 60.6% of patients with ANCA-associated glomerulonephritis. In cases with IgG deposition, electron-dense deposits (EDDs) were observed at various sites in the glomerulus, and MPO and IgG immunocomplex deposition was frequently observed along the glomerular capillary. With IgM deposition, EDDs were not obvious in the glomerular basement membrane, and MPO and IgM immunocomplex was not detected. These data suggest differential mechanism between IgG deposition and IgM deposition.

Comparison of a novel chemiluminescence enzyme immunoassay (CLEIA) with enzyme-linked immunosorbent assay (ELISA) for the determination of MPO-ANCA in patients with ANCA-associated vasculitis.

BACKGROUND: Myeloperoxidase (MPO) anti-neutrophil cytoplasmic antibody (ANCA) represents the serological hallmark of ANCA-associated vasculitis (AAV). We evaluated the analytical and diagnostic accuracy of chemiluminescence enzyme immunoassay (CLEIA) versus enzyme-linked immunosorbent assay (ELISA) for the detection of MPO-ANCA. METHODS: A total of 242 sera obtained from 51 patients with AAV and 103 patients without AAV were tested for MPO-ANCA by ELISA (NephroScholor MPOANC II) and CLEIA (the STACIA MEBLux test). Disease activity in the patients with AAV was determined based on the Birmingham Vasculitis Activity Score. We analyzed the correlations between the MPO-ANCA titers determined by the CLEIA and those determined by the ELISA, and also between the MPO-ANCA titers and the disease activity. RESULTS: The MPO-ANCA titers determined by the CLEIA (x) were strongly correlated with those determined by the ELISA (y). The correlation could be expressed by the following equation in this study: y = 1.8x + 7.7 (r = 0.96; p < 0.0001). At the cutoff value of 3.5 U/ml, the CLEIA yielded positive test results for MPO-ANCA in 73 of the 242 sera (30.2%), while at the cutoff value of 20 U/ml, ELISA yielded positive test results in 57 of the 242 sera (23.6%). The CLEIA yielded false-positive test results in 4 of the 120 sera obtained from the non-AAV patients (3.3%), whereas the ELISA yielded a false-positive result in only 1 of the 120 sera obtained from the non-AAV patients (0.8%). The sensitivity and specificity of the CLEIA for the diagnosis of AAV were 100% and 96.7%, respectively, while those of the ELISA were 94.3% and 99.2%, respectively. The sensitivity and specificity of the CLEIA for the prediction of active disease were 100% and 64.4%, respectively, while those of the ELISA were 94.3% and 73.6%, respectively. CONCLUSION: The false positivity rate of the CLEIA for MPO-ANCA tended to be high as compared with that of the ELISA. Also, according to the correlation coefficient between the results of the CLEIA and the ELISA calculated in this study, it is necessary to pay attention to the differences in the sensitivity and specificity between CLEIA and ELISA.