What happens in rheumatoid arthritis, exactly?

What is it?

Rheumatoid arthritis (RA) is a long-term condition that typically causes joints to become painful, swollen and warm. It is an autoimmune disease which means that it is caused by the body’s immune system attacking the body itself.

RA affects about 0.5% to 1% of adults in the developed world. Women are affected more often than men. In 2013, RA caused 38 000 deaths.

What causes it?

The causes of RA are quite poorly understood. About half of the risk is genetic, and smoking also seems to play a role in some people. It is not known what triggers the symptoms – since researchers haven’t been able to identify any specific triggers, it is thought that either the trigger varies or the beginning of symptoms is up to chance.

What happens during it?

The purpose of our joints is to help our bones move in relation to one another. The fluid that fills the joint capsule and the fact that the heads of our bones are covered with  the smooth and elastic cartilage help make this happen as smoothly as possible.

The synovial membrane outlines the joint capsule. It is important for many reasons – for example, it maintains the fluid and provides nutrients to the cartilage. In RA, the synovial membrane is under persistent inflammation.

RA is thought to begin when the body mistakes a certain normal molecule as something foreign and dangerous. The molecules cause a type of white cell called the T cell to become activated. The T cells start to produce inflammation-promoting cytokines. Inflammation normally happens when we are infected with a microbe, and it involves making blood vessels more dilated and more permeable to allow as many white cells as possible to come to the battle ground to fight the microbe. This means that also more fluid gets from the vessels to the tissue, and the tissue becomes swollen, red, and painful. Now there is no microbe, but the cytokines produce an inflammation in the tissues anyway, especially in the synovial membrane I previously mentioned.

These T cells also start activating other white cells called B cells. The B cells start producing cytokines too, and they also form aggregates in the joint capsule and start activating other cells. These other cells include the white cell giants called macrophages, and the macrophages residing in the synovial membrane produce huge amounts of cytokines which in turn encourage even more white cells to become activated and promote inflammation. These molecules also activate cells whose job it is to break down bone when necessary, and if this breaking down goes on for too long, you can probably imagine what kind of damage it does to the bones.

How can it be treated?

Unfortunately there is no cure for RA, but treatments can ease the pain and slow the progress of the disease. There are lots of different kinds of medications that can be used – many of them block the cytokines, which are arguably the biggest issue in RA. Exercising regularly is very useful as well.

 

 

Sources: https://en.wikipedia.org/wiki/Rheumatoid_arthritis, https://www.hopkinsarthritis.org/arthritis-info/rheumatoid-arthritis/ra-pathophysiology-2/, https://en.wikipedia.org/wiki/Disease-modifying_antirheumatic_drug, https://en.wikipedia.org/wiki/Synovial_membrane, http://www.nhs.uk/Conditions/Rheumatoid-arthritis/Pages/Treatment.aspx

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