Abstract
In several cases with IgA nephropathy (IgAN), differential diagnosis is difficult due to the complication with other systemic diseases which can induce secondary IgAN. Recently, we demonstrated that immunostaining with galactose-deficient IgA1-specific monoclonal antibody (KM55 mAb) specifically showed positive in primary IgAN cases. Here, we report four cases which we could make definitive diagnosis by immunohistological analysis using KM55 mAb. The underlying systemic diseases are rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), hepatitis C (HCV) and Crohn’s disease (CD). Renal pathological findings in the four cases revealed mesangial proliferative glomerulonephritis with IgA and C3 deposits. Immunostaining with KM55 mAb was positive for three cases complicated with RA, SLE and CD, respectively. Thus, these three cases were diagnosed as primary IgAN and treated with tonsillectomy and steroid pulse therapy. These three cases finally achieved clinical remission. On the other hand, the case with HCV showed negative for KM55. Finally, we diagnosed as HCV-related nephropathy and successfully treated by antiviral agents. These cases suggested KM55 mAb is a strong tool to differentiate primary IgAN from secondary IgAN.
Highlights
IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide
There are increasing evidences that Gd-IgA1 play a pivotal role in the pathogenesis of IgAN [7]
Elevations of serum Gd-IgA1 levels and mesangial deposition of Gd-IgA1 were reported in patients with IgAN [3, 5]
Summary
IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. It is defined as primary glomerulonephritis with predominant glomerular IgA deposition. We diagnosed as primary IgAN due to positive staining of KM55 mAb colocalized with IgA deposit area (Fig. 2). According to the diagnosis of primary IgAN, tonsillectomy with steroid pulse (TSP) therapy was performed. IF showed mesangial deposition of IgA and C3, but negative for C1q that is atypical for lupus nephritis (Fig. 1). Immunostaining with KM55 mAb was performed and showed its positive staining colocalized with IgA (Fig. 2). After discontinuation of steroid treatment, polyarthritis exacerbated and serum level of anti-ds-DNA Ab gradually elevated A renal biopsy was performed for definitive diagnosis He was diagnosed with Crohn’s disease (CD) when he was 29 years old. To distinguish primary IgAN and secondary IgAN with CD, immunostaining with KM55 mAb was performed and showed its positive staining colocalized with IgA (Fig. 2). Serum levels of IgA and Gd-IgA1 significantly decreased (Table 1)
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