*Welcome to the OutUK series looking at gay men and their health brought to you in association with the NHS* website.**
	Each week we'll tackle a different topic in our A to Z of Gay Health. We'll have features and advice on everything from relationships, sexual health, mental and physical conditions and how to stay fit. You can follow any of links provided below for more information direct from the NHS website, or see this week's feature L: Laxatives.

Causes

Rheumatoid arthritis is an autoimmune condition, which means it's caused by the immune system attacking healthy body tissue. However, it's not yet known what triggers this.

Your immune system normally makes antibodies that attack bacteria and viruses, helping to fight infection.

If you have rheumatoid arthritis, your immune system mistakenly sends antibodies to the lining of your joints, where they attack the tissue surrounding the joint.

This causes the thin layer of cells (synovium) covering your joints to become sore and inflamed, releasing chemicals that damage nearby:

bones
cartilage - the stretchy connective tissue between bones
tendons - the tissue that connects bone to muscle
ligaments - the tissue that connects bone and cartilage

If rheumatoid arthritis is not treated, these chemicals gradually cause the joint to lose its shape and alignment. Eventually, it can destroy the joint completely.

Various theories of why the immune system attacks the joints have been suggested, such as an infection being a trigger, but none of these theories has been proven.

Possible risk factors

There are several things that may increase your risk of developing rheumatoid arthritis, including:

your genes - there's some evidence that rheumatoid arthritis can run in families, although the risk of inheriting it is thought to be low as genes are only thought to play a small role in the condition
hormones - rheumatoid arthritis is more common in women than men, which may be because of the effects of the hormone oestrogen, although this link has not been proven
smoking - some evidence suggests that people who smoke have an increased risk of developing rheumatoid arthritis

Further information

National Rheumatoid Arthritis Society: possible causes and risk factors

OutUK's A to Z of Gay Health continues and you can read this week's feature L: Laxatives. We have covered many subjects in this series and you can catch up with all of our Previous A to Z Features. If you want to find out more about this particular topic you can visit the Original article on the NHS website. If you are worried by any aspect of your health make sure you go and see your doctor or book an appointment at your local clinic.
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