Sjogren's syndrome - Causes of Sjögren's syndrome

It's not known exactly what causes Sjögren's syndrome, but it's thought to be linked to a problem with the immune system.

The immune system

Your immune system usually helps protect the body from infection and illness by making antibodies. Antibodies attack bacteria and viruses, which help stop you from becoming ill.

An autoimmune condition causes your immune system to react abnormally. Instead of attacking foreign cells, such as bacteria, the antibodies start attacking your body's healthy cells and tissue.

In Sjögren's syndrome, the parts of the body usually affected are the tear, saliva and vaginal glands, which are collectively known as the exocrine glands.

The antibodies damage the exocrine glands so they can no longer function normally. There's some evidence that the immune system also damages the nerves that control these glands, which further reduces their effectiveness.

The immune system can go on to damage other parts of the body, such as muscles, joints, blood vessels, nerves and, less commonly, organs.

Possible triggers for Sjögren's syndrome

Primary Sjögren’s syndrome

Most researchers believe that primary Sjögren's syndrome is triggered by a combination of genetic and environmental factors.

Certain people are born with specific genes that make them more vulnerable to a faulty immune system. Then, many years later, an environmental factor, possibly a common virus, triggers the immune system to stop working properly.

The female hormone oestrogen also seems to play a role. Sjögren's syndrome mostly occurs in women, and symptoms usually start around the time of the menopause, when oestrogen levels begin to fall. Falling oestrogen levels can contribute to dryness, and this dryness could make the condition more noticeable.

Secondary Sjögren’s syndrome

Sjögren’s syndrome can be associated with other autoimmune conditions, such as rheumatoid arthritis or lupus. This is known as secondary Sjögren’s syndrome.

The exocrine glands

Your saliva and tear glands play a vital role in protecting your mouth and eyes, which is why the symptoms of Sjögren's syndrome can be widespread and troublesome.

The importance of tears

We usually only notice our tears when we cry, but our eyes are always covered by a thin layer of tears, known as a tear film.

Tears are made up of a mix of water, proteins, fats, mucus and infection-fighting cells. Tears serve several important functions. They:

• lubricate the eye
• keep the eye clean and free of dust
• protect the eye against infection
• help stabilise your vision

The importance of saliva

Saliva also serves several important functions, including:

• keeping the mouth and throat naturally lubricated
• aiding digestion by moistening food and containing enzymes that can break down certain starches
• acting as a natural disinfectant (saliva contains antibodies, enzymes and proteins that protect against some common bacterial and fungal infections)