Inflammation can have causes that aren't due to underlying disease. Examples include injuries such as sprains and strains, overuse or insect bites.Inflammatory diseases include a vast array of disorders and conditions that are characterized by inflammation. Examples include allergy, asthma, autoimmune diseases, coeliac disease, glomerulonephritis, hepatitis, inflammatory bowel disease, preperfusion injury and transplant rejection.
Increased blood flow and cells arrive at a given site, causing heat, swelling, pain and loss of function, but there is no infection and no trauma has occured. Attacking the body without an external insult in this way is called autoimmunity.
This is what happens in arthritis. The tissue that swells is the lining of the joint and increased fluid is produced. Together these make the joint swollen, painful and stiff to move. There is also loss of function - for example, a swollen knee makes it difficult to walk.
Inflammation can also cause:
Enlargement and loss of function of the kidney (as in SLE) Swelling and loss of function of blood vessels (as in Vasculitis) Swelling and loss of function of muscles (as in Juvenile Dermatomyositis)
The overall effect of this inflammation depends on how long it lasts.
Short periods of inflammation, such as with an allergic reaction or reactive arthritis, are generally fully resolved and leave no long term problems.
Inflammation that lasts several months or years or is particularly severe may cause lasting damage to the affected area or organ (for example, leading to deformed joints). This is what happens in arthritis.