Final answer:
Extracardiac lesions in rheumatic fever can occur in joints, nervous tissue, and heart valves. Cross-reacting antibodies cause inflammation, scarring, and stiffness of the valve leaflets, leading to irreversible damage and the development of heart murmurs.
Step-by-step explanation:
Extracardiac lesions in rheumatic fever can occur in various locations, including the joints, nervous tissue, and heart valves.
Rheumatic fever is an immune-mediated response to a bacterial infection, specifically Streptococcus pyogenes. When the body's antibodies mistakenly attack tissues that contain proteins similar to the bacteria's surface proteins, it can result in damage to extracardiac sites.
For example, joint pain and swelling occur due to the immune response targeting synovial tissues in the joints. Additionally, damage to the nervous tissue can lead to neurological symptoms.
However, the most significant extracardiac lesions in rheumatic fever usually affect the heart valves. Cross-reacting antibodies cause inflammation, scarring, and stiffness of the valve leaflets, which can lead to irreversible damage and the development of heart murmurs.