Iritis - Causes of uveitis

Uveitis occurs when the eye becomes inflamed.

Inflammation is when areas of the body become warm, red and swollen in response to a perceived threat.

This is sometimes the result of an infection, but most cases of uveitis are thought to be related to a problem with the immune system (the body's defence against infection and illness).

If the specific cause of uveitis is not identified, it is known as idiopathic uveitis. But most experts suspect that idiopathic uveitis is also related to a problem with the immune system.

Immune system problems

Uveitis often develops in people who have an underlying autoimmune condition (where the immune system mistakenly attacks healthy tissue).

Autoimmune conditions known to cause uveitis in some people include:

ankylosing spondylitis – an autoimmune condition mainly affecting the spine
reactive arthritis – a type of arthritis often affecting the joints, genitals and eyes
conditions that cause bowel inflammation, such as Crohn's disease and ulcerative colitis
psoriasis – a skin condition caused by the immune system disrupting the normal production of skin cells
multiple sclerosis – an autoimmune condition mainly affecting the nerves
Behçet's disease – a rare condition that causes mouth ulcers and genital ulcers

Infection

A minority of uveitis cases are caused by an infection, such as:

toxoplasmosis – an infection spread by parasites
the herpes simplex virus – the virus responsible for cold sores and genital herpes
the varicella-zoster virus – the virus that causes chickenpox
cytomegalovirus – a common infection that doesn't usually cause any noticeable symptoms in most people, but can cause sight-threatening uveitis in people with a reduced immune system

Other causes

In some cases, uveitis is not caused by an infection or a problem with the immune system. For example, uveitis can also be caused by:

trauma or injury to the eye(s)
some types of cancers, such as lymphoma, although this is a very rare cause of uveitis