Fibronectin is a normal plasma glycoprotein thought to have an important role in platelet aggregation and clot formation. Because of the participation of the coagulation system in hemolytic-uremic syndrome, the present study sought to determine if fibronectin plays a role in the pathogenesis of this disease. With this purpose in mind, plasma fibronectin levels were measured in 17 children with the clinical diagnosis of hemolytic-uremic syndromne and in 22 age-matched control subjects. Fibronectin levels were significantly depressed in 13 of 17(76 percent) patients with hemolytic-uremic syndrome during the acute phase of their illness. These levels did not correlate with age, sex, serum creatinine level, platelet count, or hemoglobin concentration. Serial plasma samples were available in eight of these patients: fibronectin remained depressed from two to 10 days and then returned toward the normal range concomitant with increasing platelet counts and improvement in renal function. During remission, fibronectin levels were normal in all nine patients tested. To try to determine if fibronectin is deposited in the kidney during hemolytic-uremic syndrome, kidney biopsy specimens from six patients with hemolytic-uremic syndrome were examined by immunofluorescence for the presence of fibronectin, fibrinogen, and platelet antigens. Extensive deposition of all three antigens was demonstrated along the glomerular capillary wall in all biopsy specimens. In conclusion, plasma fibronectin levels are decreased during the acute phases of hemolytic-uremic syndrome in the majority of patients. Kidney biopsy findings suggest that fibronectin is intimately involved in the activation of the coagulation system in this disease and that decreased plasma fibronectin levels in hemolytic-uremic syndrome may be due, at least in part, to accelerated consumption of the protein at the sites of injury.
