The exact cause of rheumatoid arthritis is unknown. It may be caused by the result of many factors. More than one factor is needed to trigger the disease. One factor has to do with genetics. If the disease was shown in the blood of relatives, it increases the risk of the disease. The rheumatoid factor is one of these things that may occur in the blood. Infectious factors are also possible. Certain infections or illnesses can cause one of the other factors to react. In other words, just because you have the rheumatoid factor doesn't mean you have the disease. Something else is needed to trigger the factor. Hormones can also affect the disease. Certain hormones also play a role in the progression of the disease. This depends on whether the individual is male or female.