Viruses have been suspected to be etiological agents of IgA nephropathy. Recently, viruses were detected in renal tissues from patients with IgA nephropathy. We tried to cause lesions similar to IgA nephropathy by inoculating virus into mice and to detect virus RNA in the lesion by in situ hybridization. A group of mice were inoculated intravenously with coxsackie B₄ virus once a month from 1 to 5 months of age and sacrificed monthly from 6 to 12 months of age. Mesangial proliferation and deposits that stained positive with periodic acid-Schiff in light microscopy and electron-dense deposits in electron microscopy were found from 6 months of age. Positive findings for IgG and IgA deposition in the mesangium were noted and the intensity of IgA deposition was predominant after 10 months of age. The signals of coxsackie B₄ virus by in situ hybridization were observed in the lesions. These observations indicate that coxsackie B₄ virus inoculated repeatedly into mice induces lesions similar to IgA nephropathy. The depositions of the lesions may be immune complexes of coxsackie B₄ virus and these immune complexes injure renal tissues.

We describe a method for detecting virus-specific RNA sequences using a nonradioactive enzyme system, and analyze coxsackie B4 virus (cox. B4) RNA sequences in infected mouse kidney with pathological changes. Diffuse mesangial proliferation was observed transiently 24 h after inoculation of cox. B4 virus in glomeruli. OCT-treated thin sections of the same tissue were hybridized in situ using a digoxigenin-labeled oligonucleotide probe. The strongest signal was observed in the mesangial sample. These findings suggest that the transient proliferative mesangial changes were caused by direct injury following virus infection without immune complex.

In Japanese patients idiopathic tubular proteinuria presents mainly as asymptomatic tubular low molecular weight proteinuria. This disease has recently been shown to resemble Dent’s disease which is characterized by tubular proteinuria, hypercalciuria, rickets and eventual renal failure. We report on 4 children with idiopathic tubular proteinuria. Although they had normal renal function, as evidenced by serum creatinine or creatinine clearance, they had very poor renal accumulation of ^99mTc-DMSA and the presence of large amounts of tracer in the bladder. Additionally, the patient with the largest amounts of tubular proteinuria had the poorest renal accumulation of the 4 patients. The renal accumulation of tracer decreased with time from a maximum at 10 min after injection. These findings demonstrate that the tracer, once taken to be confined to the proximal tubular cells, is immediately excreted to the tubular lumen. We suggest that poor renal accumulation of ^99mTc-DMSA is very important in elucidating the mechanism of idiopathic tubular proteinuria, and that ^99mTc-DMSA renoscintigraphy is useful in the evaluation of the patient’s renal function over time.

The purpose of the present investigation is to study renal injury by monthly viral inoculation into mice, using several different types of strains of enterovirus. A group of mice were inoculated intravenously with five different serotypes of group B coxsackieviruses (CB1 to CB5), once a month from 1 to 5 months of age and sacrificed monthly from 6 to 12 months of age. Mesangial proliferation and PAS-positive mesangial deposits in light microscopy and electron-dense deposits in electron microscopy were observed at maximum from 6 to 7 months of age. The CB viral RNA detected by in situ hybridization were observed in the mesangial lesion. By immunofluorescence findings, positive findings for IgG and IgA were observed. These results demonstrated that intermittent intravenous inoculation with different serotypes CB in mice provoked pathological changes closely resembling those in human proliferative glomerulonephritis. Moreover, the detection of CB viral RNA in glomerular lesions suggested that renal injury was induced by immune complexes correlated with CB viral replication in renal tissues.

A case of Sjögren's syndrome with glomerulonephritis is presented. The patient was a 13 year old male with hematuria and proteinuria discovered by urine screening of school children. Evaluation showed no evidence of any associated connective tissue disease. Kidney biopsy was consistent with membranous glomerulonephritis. Sjögren's syndrome with membranous glomerulonephritis is rare and the patient was the youngest case in the literature.