Lupus

What is lupus, and how common is it?

Lupus is a long-lasting (chronic) autoimmune condition, which means your immune system attacks your body's own tissues¹. The main form is systemic lupus erythematosus (SLE), and it is the most common and most serious type². The inflammation it causes can reach almost any part of the body, most often the skin, joints, kidneys and blood³⁴.

Worldwide, an estimated 43.7 in every 100,000 people have SLE, although the true figure is uncertain⁵. It is far more common in women than in men⁵. It can start at any age, and 15–20% of people develop it in childhood⁶.

What causes lupus, and who gets it?

No one knows the exact cause³. SLE usually arises when an environmental exposure meets a person whose genes carry enough risk variants⁴. Hormones are also thought to play a part, and you are more likely to have lupus if a blood relative has it³. Genes aren't the whole story, because identical twins are not always both affected⁴.

The highest risk is among women of reproductive age⁴. Worldwide, SLE is more common in people of South Asian, East Asian and other non-White ancestry than in White people⁶. Recognised triggers include sunlight, hormonal changes such as puberty or pregnancy, and some medicines⁷. Current smoking has been linked with developing SLE, while former smoking has not, and stopping smoking has been suggested as a first step in preventing and treating it⁸.

What does lupus feel like, how is it diagnosed, and what can make it serious?

What does it feel like?

Lupus varies widely. Features range from mild (a rash or arthritis) to life-threatening organ problems, and it is hard to predict which a person will get⁴. Common features include:

• Joint pain, usually in several small joints and often without swelling⁷. Some people have painful, swollen joints with morning stiffness¹.
• Skin rashes, including a butterfly-shaped rash across the face³. Rashes that react to sunlight are more specific to lupus⁷.
• Painless sores inside the nose and mouth¹.
• Fingers and toes that change colour (blue-purple, white or red) with cold or stress, known as Raynaud's phenomenon¹.
• Heavy tiredness² and swelling in the legs or around the eyes¹.

Because the symptoms aren't specific to lupus, early diagnosis can be difficult².

Foot problems are common in people with SLE. Many have had foot pain, and Raynaud's phenomenon, chilblains, bunions (hallux valgus), fungal nails and leg pain when walking are all reported⁹. People with SLE are also more likely to have an abnormal ankle brachial index (a comparison of blood pressure at the ankle and the arm), which can point to reduced blood flow in the legs and feet⁹. That is a pattern across groups of people and doesn't show harm in any one person. Foot health research in lupus also highlights circulation problems, nerve problems, deformity, and skin and nail problems⁹.

How is it diagnosed?

No single test diagnoses lupus¹⁰. Diagnosis combines symptoms, an examination, and blood and immune tests, and it is made by clinicians experienced in managing lupus⁶. It shouldn't be made without at least one autoantibody (an antibody against the body's own tissues) or low complement (a measure of immune activity in the blood)⁶. Each feature is also worked out: is it from lupus activity, organ damage, a medicine's side effects, infection, clots or another condition⁶?

What can make it serious?

Kidney inflammation and blood clots can be life-threatening, and it is hard to predict who will get them⁴. Lupus can also damage the heart and lungs² and inflame blood vessels (vasculitis)¹. About a third of people with lupus have antiphospholipid antibodies, which make the blood "sticky" and can cause strokes, clots in the leg or lungs, and pregnancy complications². Corticosteroids and immunosuppressants raise the risk of serious infection, and guidance advises vaccination for people taking immunosuppressants⁷¹¹.

What else could it be?

Lupus symptoms can mimic other disorders². One example is undifferentiated connective tissue disease (autoimmune symptoms that don't yet fit a single diagnosis). In some people it later turns into SLE or rheumatoid arthritis, usually within 5–6 years¹².

What can I do myself, and what treatments come first?

Lupus is managed with medicines, alongside everyday steps.

Hydroxychloroquine is the foundation of treatment. Guidelines recommend it for everyone with lupus unless it can't be used, with the dose kept within a weight-based limit¹¹⁶. It can cause an eye problem (retinopathy) that isn't reversible and has no treatment. The risk rises with higher doses and longer use, and kidney disease is another major risk factor. Guidance sets a weight-based maximum, a baseline eye exam, and yearly screening starting after 5 years of use, or earlier if there are major risk factors¹³.

Glucocorticoids (steroid medicines) are used short term, or as "bridging" treatment, during active disease. Long-term oral steroids aren't routinely recommended because of their harms, so guidelines advise using the lowest amount possible and stopping them when possible⁶¹¹¹⁴.

Sun protection is the main everyday step. Guidelines advise a high-SPF, broad-spectrum sunscreen that blocks both UV-A and UV-B⁶. Vitamin D supplements are often used when sunlight is being avoided⁷. Guidelines give hydroxychloroquine and careful steroid use the strongest backing, so these are the steps most agreed on.

What helps if the first treatments aren't enough?

Hydroxychloroquine stays the base of treatment, and steroid exposure is still kept as low as possible⁶. A newer cell-based treatment, CAR T-cell therapy, has been tried in SLE. It caused cytokine release syndrome (an inflammatory reaction) in over half of the people treated, almost all of it mild or moderate. Some people had nervous-system side effects, and some had serious infections, including one death from meningitis¹⁵.

How long does lupus last, and can flares be prevented?

Lupus is lifelong and has no cure¹⁰. Its course differs from person to person.

Memory and thinking problems affect about 38% of people with SLE. They can be subtle and easy to miss⁶. Low mood and depression are also part of caring for lupus, and screening and treatment are advised⁷.

Whether sun protection prevents flares that affect the whole body isn't clear, because the studies are of low quality, but guidelines still advise it⁶.