Adult primary IgA nephropathy and common viral infections

The clinicopathologic data of 237 Chinese patients with IgA nephropathy from Hong Kong are reviewed in an attempt to identify the features pertinent to Chinese patients. Although the nephropathy is commonest in the 26-35 year age group, 11% of the IgA nephritic patients were children below 16 years. The male predilection reported in Caucasian populations is not observed and the male:female ratio is 0.94 in our series. The commonest renal manifestation is microscopic hematuria (25%) and 19% of the patients present with macroscopic hematuria, not infrequently synpharyngitic. Nephrotic syndrome occurs in 15% of our patients and proteinuria more than 1 gm/day is documented in 58% of these IgA nephritic patients. The degree of proteinuria does not correlate with prognosis. A small proportion of these nephrotic patients respond to steroid therapy, suggesting a variant of IgA nephropathy that resembles lipoid nephrosis in its steroid-responsiveness. Seventeen percent of the patients (18/104) are hepatitis B virus carriers and 61% of these patients demonstrate viral antigens in their renal biopsies, indicating that hepatitis B virus infection may sometimes play a pathogenetic role.

Five adult cases of IgA nephropathy associated with chronic hepatitis B virus infection were studied. Serum HBsAg and anti-HBc were present in five patients and HBeAg in four patients. Glomerular changes were typical of primary IgA nephropathy in four patients, and a mixed picture of IgA and membranous nephropathy was demonstrated in one patient. Immunofluorescence microscopy using polyclonal and monoclonal antibodies against HBsAg, HBcAg, and HBeAg revealed mesangial deposits of HBsAg in renal biopsies from four patients. One renal biopsy showed only mesangial and capillary HBcAg by polyclonal antiserum, and virus-like particles were demonstrated in the intramembranous electron-dense deposits on ultrastructural examination. Mesangial HBeAg was not detected in the renal biopsies from these patients with IgA nephropathy. As for the single patient with a mixed picture of IgA and membranous nephropathy, granular deposits of HBeAg with a distribution similar to IgG were detected in the glomerular capillary walls in addition to the mesangial deposition of HBsAg. These findings suggest that HBsAg rather than HBeAg may play a role of the pathogenesis in some of the adult patients with IgA nephropathy associated with chronic hepatitis B virus infection.