A comparative study of IgA nephritis in Japan and Germany. An approach to its geopathology

A comparison of clinical and pathological features in 357 Japanese cases and 29 German cases of primary IgA nephritis was performed. Male population was higher than female in the German cases (2.6:1), while it was almost even in the Japanese (1.07:1) (p less than 0.05). Age distribution was similar. At the time of detection of the disease, asymptomatic patients were more frequent in Japanese (78%) than in German cases (60%) (p less than 0.05). The most common findings were mild mesangial proliferative glomerulonephritis in both series (65% in Japanese, 61% in German cases), but severe histological changes were more frequent in German patients (25%) than in the Japanese (16%). The incidence of IgA nephritis in primary glomerulonephritis was 38.8% in Japanese and 11.9% in German cases, and the incidence in mesangial proliferative glomerulonephritis was 65.6% in Japanese and 29.2% in German patients (p less than 0.01). It is considered that the divergent incidence of IgA nephritis may be a real geopathological event, although its variability may be intensified by different indications for biopsy or different population. It is suggested that various possible pathogenetic agents may be irregularly distributed throughout the world, which may contribute to the divergent clinical and pathological manifestations.