What are autoimmune diseases?

Your handy guide to finding out what causes them, who gets them & six of the most common types

Our immune system is a wonderful thing. It’s made up of lots of different cells, tissues and organs, all working together to help keep our bodies fighting fit. It defends against illness and infection, by destroying any unfamiliar cells such as viruses and bacteria.

Autoimmune diseases develop when the immune system struggles to tell the difference between its own cells and foreign cells. It then mistakenly attacks the body’s own cells, thinking they’re harmful. An autoimmune disease can affect a specific part of the body or can affect the entire body.

What causes autoimmune diseases?

The exact cause of autoimmune diseases is unknown. Environmental factors and genetics are thought to play a role, as autoimmune conditions often run in families. Studies have also shown that women are far more likely to develop an autoimmune condition than men.

How many different autoimmune diseases are there?

There are over 80 different types of autoimmune diseases, many of which share the same symptoms. Let’s look a little closer into six of the most common types, to find out more about what they are, the different symptoms and how they’re treated.

Type 1 diabetes

The hormone insulin helps to control blood sugar levels. Type 1 diabetes is a lifelong condition where blood glucose levels are too high because the body can’t produce insulin. This happens because the immune system mistakenly destroys the cells in the pancreas that make insulin. Symptoms include:

• Feeling very thirsty

• Feeling very tired

• Losing weight without trying

• Peeing more than usual, often at night

• Blurred vision

Although type 1 diabetes can start at any age, it’s usually diagnosed in childhood. Once diagnosed, those with type 1 diabetes will need to take insulin for the rest of their lives, usually through injections, using an insulin pen or an insulin pump. They’ll also need to regularly test their blood sugar levels.

Coeliac disease

Coeliac disease is a condition where eating gluten causes the immune system to attack the small intestine. This damages the lining of the intestine, making it difficult for the body to take in nutrients. It’s thought to affect around one in every 100 people in the UK. Symptoms include:

• Constipation

• Indigestion

• Feeling very tired

• Losing weight without trying

• Stomach bloating

• Diarrhoea

Although there’s no cure for coeliac disease, following a gluten-free diet should help to control symptoms. This is important even if you only have mild symptoms, as carrying on eating gluten can lead to serious complications.

Rheumatoid arthritis

Rheumatoid arthritis is a long-term condition where the immune system attacks the cells that line the joints. The condition usually affects the hands, feet and wrists and over time can damage the joints, cartilage and bone. Symptoms include:

• Joint pain

• Swelling and stiffness which can come and go, or change over time

Currently there's no cure for rheumatoid arthritis, but early treatment and support can reduce the risk of joint damage. Treatment for the condition usually involves care from a GP and several different specialists.

Multiple sclerosis

Multiple sclerosis (MS) is a condition that affects the brain and spinal cord. The immune system attacks the layer th