Question
Name two important non-suppurative complications of streptococcus pyogenes
Answer
Two important non-suppurative (post-streptococcal immune-mediated) complications of Streptococcus pyogenes (Group A Streptococcus) infection:
-
Acute rheumatic fever — follows streptococcal pharyngitis (not skin infection), occurring 2–4 weeks after the initial throat infection; caused by molecular mimicry, in which antibodies raised against the streptococcal M protein cross-react with cardiac myosin/valve tissue and other host antigens, causing carditis (with potential long-term valvular damage, particularly mitral valve), migratory polyarthritis, Sydenham’s chorea, subcutaneous nodules, and erythema marginatum (Jones criteria).
-
Acute post-streptococcal glomerulonephritis (PSGN) — can follow either streptococcal pharyngitis or skin infection (impetigo), typically 1–3 weeks (pharyngitis) or 3–6 weeks (skin infection) after the initial infection; caused by deposition of circulating immune complexes (streptococcal antigen-antibody complexes) in the glomerular basement membrane, triggering complement activation and glomerular inflammation, presenting with haematuria (smoky/cola-coloured urine), oedema, hypertension, and reduced urine output.
Both conditions are immune-mediated (antibody/immune-complex-driven) rather than resulting from direct bacterial invasion of the affected organ, which is why they occur as delayed sequelae after the primary infection has often already resolved.