Systemic Lupus Erythematosus

Systemic Conditions Affecting the Feet· Also known as: lupus, SLEUpdated Nov 2026

Reviewed by Andrew Schox, BSc(Hons) PGradDipPod MPod, November 2026

At a Glance

Systemic lupus erythematosus (SLE, often just called lupus) is a long-term autoimmune condition. Your immune system, which normally fights germs, attacks your own tissues instead. It affects roughly 1 in 1000 adults, and far more women than men. Common features are joint pain, rashes that react to sun, mouth sores and fingers or toes that change colour in the cold. It is different for everyone, from mild to serious. There is no cure, but medicines and sensible daily habits help many people keep it under control.

What is it?

Systemic lupus erythematosus (SLE) is a long-term (chronic) autoimmune condition. In an autoimmune condition, the immune system turns on the body's own tissues. This causes inflammation, which can reach many parts of the body. The skin, joints, muscles, kidneys and blood are affected most often.

There are several types of lupus. SLE is the most common and the most serious of them. It is highly variable: one person may have only a rash and sore joints, while another has problems with their organs.

SLE can't be cured. Treatment aims to keep it quiet and protect your organs.

Who does it affect?

Around 1 in 1000 adults have SLE. Another way of counting gives about 43.7 people in every 100,000. Estimates differ because they come from different groups of people and are worked out in different ways.

Women are affected far more than men: about 78.73 per 100,000 women compared with 9.26 per 100,000 men. It often starts during the childbearing years. It can begin at any age, and 15 to 20 per cent of people develop it in childhood. The gap between girls and boys is smaller before puberty.

SLE is more common in people of South Asian, East Asian and other non-White ancestry. Having a close blood relative with lupus also raises the chance.

Signs and symptoms

SLE looks different from person to person, and it is hard to predict which features someone will get. Common ones include:

Joint pain, often in several small joints, sometimes with swelling and morning stiffness.
Skin rashes, including a butterfly-shaped rash across the face. Rashes that flare in sunlight are more typical of SLE.
Painless sores inside the mouth or nose.
Fingers and toes that turn blue-purple, white or red in the cold or when stressed (Raynaud's phenomenon).
Heavy tiredness, and puffy legs or puffy skin around the eyes.
Problems with memory and thinking, which affect about 38 per cent of people with SLE and are easy to miss.

The feet are often involved. About 3 in 4 people with SLE have had foot pain at some point, and about 1 in 3 have it now. About half have Raynaud's phenomenon, and about half have had leg pain when walking (intermittent claudication). About 3 in 10 have a bunion (the big toe angling towards the other toes), a bit over 1 in 4 have chilblains, and about 15 per cent have a fungal nail infection.

Some features can mean the condition is more serious. Severe lupus can inflame and damage the heart, lungs, brain or kidneys, and kidney inflammation or blood clots can be life-threatening. These are hard to predict. About a third of people with lupus have antiphospholipid antibodies, which make the blood "sticky" and can lead to strokes, clots in the leg or lung, and pregnancy problems. Lupus can also inflame blood vessels (vasculitis).

People with SLE are more likely to have a poor result on an ankle brachial index test, which compares blood pressure at the ankle and arm. A poor result can mean reduced blood flow to the legs and feet. Medicines that calm the immune system, such as steroid tablets and immunosuppressants, also make serious infections more likely.

Because the symptoms are not specific, they can look like other conditions. Doctors work out whether each problem comes from lupus activity, damage to an organ, a medicine's side effects, an infection, a clot or another condition. In the feet, poor circulation or nerve damage (peripheral neuropathy) can have their own causes. A related condition called undifferentiated connective tissue disease has similar features. About 28 per cent of people with it go on to develop SLE or rheumatoid arthritis, most within 5 to 6 years.

What causes it?

The exact cause isn't known. SLE usually develops when a person who carries many gene variants that raise risk meets something in their environment. Hormones are also believed to play a part. Genes are not the whole story, because identical twins are not always both affected.

Sunlight, hormonal changes (such as puberty or pregnancy) and some medicines are known triggers. People who currently smoke are more likely to develop SLE. This was not seen in people who used to smoke.

How is it diagnosed?

There is no single test for SLE. The diagnosis combines your symptoms, an examination, blood tests and other immune markers. It is best made by doctors with experience in lupus, and a lupus centre may be involved when the picture is unclear.

The diagnosis shouldn't be made without at least one autoantibody (an immune protein that targets your own tissues) or low levels of complement (immune proteins that can be used up in lupus). A positive antinuclear antibody (ANA) blood test is the starting point for the classification criteria. These then score features such as rashes, joint problems and kidney findings, and a score of 10 or more points counts as SLE. The criteria help doctors, but they do not make the diagnosis on their own.

Treatment

Care is usually led by a doctor who specialises in lupus, and the plan depends on your situation and preferences.

Looking after it at home

Sun protection is a big part of daily care:

Use sunscreen of factor 50 or higher.
Wear a hat.
Avoid direct sun and long periods under fluorescent lights.

It isn't clear how well sun protection prevents flares that affect the whole body, but it is still advised. Vitamin D is advised for people who avoid the sun. Depression is common enough that it is checked for. Pneumococcal and flu vaccines are advised for people taking immunosuppressants.

Treatment from your rheumatologist

Hydroxychloroquine is the foundation of treatment. It is recommended for everyone with SLE unless there is a reason they can't take it. The dose is capped by your actual body weight. It can rarely damage the retina at the back of the eye, and this damage can't be reversed. The risk rises with high doses and long use, and with kidney disease or the medicine tamoxifen. Because of this, the eyes are checked at the start, and then yearly from after 5 years (earlier if there are major risk factors).

Steroid tablets (corticosteroids) can be valuable for a short time, to bridge a period of active disease. Long-term steroid use is discouraged because of its harms. The aim is to use as little as possible and stop when possible.

Other options

Other medicines are used when hydroxychloroquine is not enough. A newer approach is CAR T-cell therapy. Side effects are common: a strong immune reaction called cytokine release syndrome affected 56 per cent of people, though almost all cases were mild or moderate. Nervous system side effects occurred in a few people. Serious infections occurred in 7.6 per cent, including one death from meningitis.

Recovery

SLE is lifelong. It tends to come and go, and it varies a great deal. A diagnosis at an early age is more often linked to a more severe course.

Checking for antiphospholipid antibodies is advised, because they raise the risk of clots and pregnancy complications. Doctors also assess infection risk and heart and blood vessel risk. Lupus can cause complications in pregnancy, so risks and medicines are often reviewed before a planned pregnancy. Problems with memory and thinking are common and may need specific questions to find.

Preventing it

No one knows how to prevent SLE from starting, because the cause isn't fully understood. Avoiding known triggers, mainly strong sun, is the main way to try to prevent flares. For people who smoke, stopping is suggested as a first step in preventing the condition. This applies to developing SLE, and it is not shown to prevent flares.

Frequently asked questions

Why are my eyes checked when I take hydroxychloroquine?

Hydroxychloroquine can, uncommonly, damage the retina, and that damage can't be reversed. Checking the eyes at the start and then regularly means any change can be caught early. The check is done yearly from after 5 years, sooner with risk factors.

Why does lupus affect women more than men?

The full reason isn't known. Hormones are believed to play a part, which fits with lupus most often starting in the childbearing years. The difference between girls and boys is smaller before puberty.

Can I have a baby if I have lupus?

Lupus can cause complications in pregnancy, especially if you have antiphospholipid antibodies. Many people with lupus plan pregnancy with their doctor beforehand, so that risks can be reviewed and medicines checked.