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 that surrounds and protects the nerves called the myelin sheath. This damages the sheath and slows down the messages travelling along the nerves. MS symptoms vary widely from person to person, and can affect any part of the body. The main symptoms include:

• Feeling very tired

• Difficulty walking

• Blurred vision

• Numbness or tingling in different parts of the body

• Muscle stiffness and spasms

• Problems with balance and co-ordination

Symptoms may also come and go in phases or get steadily worse over time. There's no cure for MS, but there are treatment options to help control the condition. These depend on the specific symptoms and difficulties a person has.

Hashimoto's disease

Hashimoto's disease or Hashimoto’s thyroiditis, is a condition where the immune system attacks the thyroid gland. The thyroid gland makes hormones that control many activities in the body. In those with Hashimoto's disease, the immune system makes antibodies that attack the thyroid gland. The condition is the most common type of autoimmune reaction that causes an underactive thyroid (hypothyroidism). As the thyroid is damaged over time, it's unable to produce enough thyroid hormone. This leads to symptoms including:

• Feeling very tired

• Being sensitive to the cold

• Weight gain

• Low mood

• Muscle aches and weakness

• Dry and scaly skin

• Weak hair and nails

Hashimoto’s thyroiditis can’t be cured, but symptoms can be treated with a medicine used to replace the missing thyroid hormone.

Graves' disease

Graves' disease is another autoimmune condition that affects the thyroid. It’s one of the most common causes of hyperthyroidism. Around three in every four people with an overactive thyroid have Graves' disease. With this disease, the immune system attacks the thyroid and causes it to make more thyroid hormone than the body needs. Common hyperthyroidism symptoms include:

• Feeling nervous, anxious and irritable

• Finding it difficult to sleep

• Being sensitive to the heat

• Heart palpitations

• Losing weight without trying

• Swelling in the neck from an enlarged thyroid gland

An overactive thyroid (hyperthyroidism) is usually treatable. You'll usually be referred to a specialist in hormonal conditions (endocrinologist) who will plan your treatment.

As always, if you’re experiencing any symptoms and you’re worried, speak to your GP about how you’re feeling. They’ll be able to listen and advise you on any treatment options.