The exact cause of rheumatoid arthritis is unknown.
Rheumatoid arthritis is an autoimmune disease, which means the body's immune system mistakenly attacks healthy tissue.
Age- Rheumatoid arthritis can affect anyone including children (known as juvenile rheumatoid arthritis). However, it usually occurs between 30-50 years of age.
Sex- Women are affected more than men in the ratio of 3:1, and it goes into remission when they are pregnant. Symptoms increase after a baby is born.
Tissue type- Tissue type is another underlying factor, in which people with Human Leukocyte Antigen (HLA) DR4 are 7 times more likely to develop rheumatoid arthritis than others.
Heredity- Relatives of people with rheumatoid arthritis are more prone to develop the disease than others.
Infections- People affected with infectious diseases like diphtheria, measles etc. have an increased risk of developing the disease.