What causes acute Rheumatic fever?

Acute rheumatic fever (ARF) is caused by an autoimmune reaction that occurs in response to a bacterial infection, specifically an infection caused by the bacteria Streptococcus pyogenes, also known as group A Streptococcus (GAS).

Here's the sequence of events that leads to ARF:

1. Streptococcal Infection: An individual contracts a streptococcal infection, which can manifest as tonsillitis (inflammation of the tonsils), pharyngitis (inflammation of the throat), or scarlet fever (a rash accompanied by sore throat and fever).

2. Body's Immune Response: The immune system mounts an immune response to fight the bacterial infection. This involves the production of antibodies that target the bacteria.

3. Cross-Reactivity: Unfortunately, some of these antibodies produced during the immune response to GAS infection cross-react with certain proteins in the heart, joints, and other tissues. This cross-reactivity is thought to be the underlying cause of ARF.

4. Inflammation and Damage: The antibodies mistakenly target and attack the tissues, leading to inflammation and damage. This inflammation affects various organs, most commonly the heart, joints, skin, and nervous system.

5. Symptoms of ARF: The inflammation and damage caused by the immune response result in the symptoms commonly associated with ARF, such as joint pain and swelling (polyarthritis), fever, fatigue, carditis (inflammation of the heart), and potentially severe heart complications (e.g., valvular damage).

It's important to note that ARF is a rare but serious complication that can develop in some individuals after a streptococcal infection, particularly when proper treatment for the infection is not sought or delayed. Prompt diagnosis and appropriate antibiotic treatment of the underlying streptococcal infection can help prevent the development of ARF.