Asymptomatic poststreptococcal glomerulonephritis in relatives of patients with symptomatic glomerulonephritis. Diagnostic value of endostreptosin antibodies.

Our previous studies have shown that endostreptosin (ESS), a cytoplasmic protein of group A streptococci, in all probability is the causative agent of poststreptococcal acute glomerulonephritis (PSAGN). Elevated antibody levels to ESS have been shown to be diagnostic for PSAGN and to correlate well with the course of the pathologic disease process. One hundred and twenty-one completely asymptomatic family members of 29 index patients with overt PSAGN were studied. Of these 121 asymptomatic family members, 26 (21.5%) had two or more abnormalities warranting a diagnosis of asymptomatic glomerulonephritis (GN): proteinuria/hematuria (18), low C3 (10 less than 85 mg/dl), high antibody titers to streptolysin O (15). Twenty-three (88.5%) of these family members with evidence of asymptomatic GN had a significant elevation of ESS antibody titers. The mean arithmetic titer for the complement fixation test was 1:24 (normal less than 1:7.5) and the mean ELISA value 0.154 (normal less than 0.075). With a certain percentage of PSAGN cases, especially adults, progressing to chronicity, the ESS antibody determinations by complement fixation and/or ELISA may be simple methods to detect and to follow-up such asymptomatic patients at risk. The high incidence of asymptomatic PSAGN (26/121) in family members of patients with overt PSAGN makes these data very significant in respect to the question of the origin of chronic glomerulonephritis without a history of overt PSAGN. Since chronic PSAGN is probably a sequel of an undiagnosed, asymptomatic disease, it may contribute materially to the contingent of end-stage renal disease.