What is a potential complication of untreated streptococcus pyogenes infection?

A potential complication of untreated Streptococcus pyogenes infection is rheumatic fever. This serious inflammatory condition can develop following infections, particularly streptococcal pharyngitis, when the body's immune response mistakenly attacks its own tissues, particularly in the heart, joints, skin, and nervous system.

Rheumatic fever typically manifests two to three weeks after the initial streptococcal infection and can lead to long-term complications, including rheumatic heart disease, which can cause permanent damage to heart valves. Therefore, prompt treatment of streptococcal infections with antibiotics is crucial to prevent rheumatic fever and its associated complications.

The other options presented do not generally arise as direct complications of untreated streptococcal infections. Chronic fatigue syndrome and chronic cough are nonspecific conditions that do not have a direct link to Streptococcus pyogenes. Infectious mononucleosis is primarily caused by Epstein-Barr virus, not by streptococcal bacteria. Thus, the association of rheumatic fever with untreated Streptococcus pyogenes infection makes it the correct answer in this context.