Final answer:
Rheumatic fever and its associated Sydenham chorea are caused by an autoimmune reaction to antigens from the Streptococcus pyogenes bacterium, leading to heart muscle damage and potential heart valve inflammation, known as carditis. Prompt treatment of streptococcal infections reduces the occurrence of this condition. Autoimmune damage is often exacerbated by molecular mimicry between the M protein of bacteria and proteins in the heart.
Step-by-step explanation:
Sydenham chorea occurs in rheumatic fever due to an autoimmune reaction to antigens from Streptococcus pyogenes, the bacterium that causes strep throat. The antibodies or T cells react with cardiac myosin, a protein found in heart muscle, which shares structural similarities with the bacterial surface proteins. This leads to autoimmune attacks that damage the heart muscle and cause rheumatic fever.
The most serious consequence of these autoimmune attacks can be the damage to and inflammation of the heart, particularly the heart valves, known as carditis. If not treated properly, this condition can lead to chronic heart disease and is worsened by repeated episodes.
Despite being rare in countries with widespread access to healthcare and early treatment of streptococcal infections, rheumatic fever remains a significant health concern in parts of the world where early diagnosis and treatment are not always available.