Recurrence of acute poststreptococcal glomerulonephritis.

Recurrence of acute poststreptococcal glomerulonephritis (APSGN) is a rare phenomenon. We present an 8-year-old boy with a second episode of APSGN 12 months following a complete clinical recovery from his initial attack. Renal histology, obtained from renal biopsies of the patient during the second attack, showed diffuse endocapillary proliferation, granular deposition of C3, IgG, IgA, and fibrinogen along capillary walls, and subepithelial electron-dense deposits. A new streptococcal cytoplasmic antigen (nephritis-associated plasmin receptor protein, NAP1r), which was recently identified as the pathogenic antigen in APSGN, was detected in the glomeruli of an early kidney biopsy specimen from the patient during the second attack of APSGN, using fluorescein isothiocyanate-labeled rabbit anti-NAP1r. However, antibodies against NAP1r, examined by Western blotting, were not present in sera from the patient. These results suggest that recurrence of APSGN in some patients may be caused by an absence of a natural immune response to NAP1r.