Nationwide and long-term survey of primary glomerulonephritis in Japan as observed in 1,850 biopsied cases

Primary chronic glomerulonephritis is the most common cause of end-stage re nal failure in Japan. The incidence in dialysis patients in Japan is about four times higher than in the United States for reason which are unclear. W e conducted a nationwide survey on the natural history and treatment of pri mary glomerulonephritis under a program project from the Ministry of Health and Welfare of Japan entitled 'Progressive Chronic Renal Disease'. We anal yzed patient characteristics, disease onset, clinical data, and histologica l findings in 1,850 patients with primary glomerulonephritis from 53 instit utions in 1985 who underwent renal biopsy at least 5 years ago, and the fol low-up study was carried out 8 years after registration. The incidence of d iffuse-mesangial proliferative glomerulonephritis is 41.9%, that of minor g lomerular abnormalities 17.5%, and that of focal-mesangial proliferative gl omerulonephritis 13.0%. Of 1,045 biopsy specimens that were examined by imm unofluorescence microscopy, 47.4% showed IgA nephropathy. Half of all cases with primary chronic glomerulonephritis were asymptomatic and were detecte d on routine health examination. The survival rates at 20 years from the ap parent onset or earliest known renal abnormality are: focal glomerular scle rosis 49%, membranoproliferative glomerulonephritis 58%, diffuse-mesangial proliferative glomerulonephritis 66%, focal-proliferative glomerulonephriti s 81%, membranous nephropathy 82%, minor glomerular abnormalities 94%, and IgA nephropathy 61%. In conclusion, a high incidence of IgA nephropathy and a better renal survival of membranous nephropathy are the features of prim ary chronic glomerulonephritis in Japan. This high incidence of IgA nephrop athy together with its poor prognosis is probably the reason for the increa sed incidence of primary chronic glomerulonephritis in dialysis patients in Japan. In addition, the importance of routine health examination including urinalysis is demonstrated.