Schistosomal glomerulopathy: selection factors

Of several hundreds of millions of people infested with schistosomiasis, only a few hundreds have, so far, been documented to have one or other of the three schistosoma-associated immune-mediated glomerulopathies, namely proliferative glomerulonephritis, focal and segmental sclerosis, and amyloidosis. Regardless of undoubted under-reporting, some factors must be involved in the selection of those who develop such glomerulopathies. On the basis of experimental and clinical evidence, this review highlights the importance of parasitic species, associated salmonellosis, genetic predisposition and impaired hepatic macrophage activity. It also discusses the potential pathogenic role of the prevailing parasite 'strains', intensity of infestation, associated infections with hepatitis B, and common urinary pathogens and impairment of hepatocellular function. Selection ultimately seems to be multifactorial, but there is evidence that inefficiency of the hepatic macrophage system plays a key role by allowing both schistosomal antigens and IgA polymers to escape hepatic clearance and/or modulation.