Psoriatic arthritis: symptoms, diagnosis and treatment

The NHS lists pain, swelling and stiffness in one or more joints, swollen fingers or toes, changes in the colour of nails or tiny dents or pits in them, and feeling drained of energy. It says symptoms can be worse first thing in the morning and may improve with exercise, which is a hallmark of inflammatory rather than wear-and-tear arthritis. Arthritis UK describes stiffness that feels worse after rest and lasts longer than 30 minutes.

Two features are particularly characteristic. Dactylitis is swelling of a whole finger or toe, the so-called sausage digit. Enthesitis is inflammation where tendons and ligaments attach to bone, commonly at the back of the heel or sole of the foot near the heel, and sometimes at the knees, hips, elbows and chest. Because they produce pain outside the joint itself, people may not connect them with arthritis.

• Swollen, stiff or painful joints that keep returning.

• A finger or toe swollen along its whole length.

• Heel or foot pain, especially on first standing.

• Pitting, ridging or lifting of the nails.

• Persistent fatigue.

The NHS describes psoriatic arthritis as a long-term condition that causes joint pain, swelling and stiffness, and notes that some people with the skin condition psoriasis will get psoriatic arthritis as they get older. Like psoriasis, it is caused by the immune system attacking healthy tissue. Arthritis UK describes it as a type of spondyloarthritis, a group of related inflammatory conditions, and says it is not contagious.

The skin and joint disease do not always run in step. Arthritis UK says some people develop psoriatic arthritis before psoriasis appears, and in rare cases people have psoriatic arthritis and never have noticeable patches. The NHS says it can sometimes develop after you have had psoriasis for many years, and that it is not clear why some people with psoriasis get it and others do not.

The NHS says medicines are the main treatment and that if one does not help, another may work better. Non-steroidal anti-inflammatory drugs, as tablets, creams or gels, can help mild symptoms. Steroid injections into a joint ease pain. Disease-modifying anti-rheumatic drugs are used for moderate to severe symptoms and can take several months to work, so they should be continued even if there is no immediate effect. Biological treatments, usually given by injection, are used if DMARDs do not help.

Arthritis UK adds that methotrexate, sulfasalazine and leflunomide can be used early after diagnosis, that many DMARDs also treat psoriasis, and that regular blood tests and blood pressure checks accompany them. It notes steroid injections into the same joint are usually limited to no more than three a year. Physiotherapists teach joint-strengthening exercise and occupational therapists suggest adjustments at home and at work, and podiatry may help with insoles and footwear.

The NHS says psoriatic arthritis is caused by the immune system attacking healthy tissue, and that it is not clear why some people with psoriasis get it and others do not. It can sometimes develop after you have had psoriasis for many years.

Arthritis UK says the genes you inherit can make you more likely to develop it, and that if you carry such genes, an infection, an accident or injury, being overweight or smoking may then trigger it. It also notes there is an element of chance, and that it might not be possible to say for certain what caused the condition. It is not contagious.

The NHS advises seeing a GP if you have joint pain, stiffness and swelling that keeps coming back, even if you do not have psoriasis. The GP may refer to a rheumatologist, and tests may include blood tests, a joint fluid test, X-rays, ultrasound and MRI scans. NICE guideline NG65 recommends that people with suspected new-onset inflammatory arthritis be urgently referred to a rheumatologist, and that people with dactylitis be referred for assessment, and warns that peripheral presentations can be misdiagnosed because problems can move between joints.

Arthritis UK says there is no specific test for psoriatic arthritis, so diagnosis rests on symptoms and examination, with blood tests for rheumatoid factor and anti-CCP antibodies, which people with psoriatic arthritis tend not to have, used to help separate it from rheumatoid arthritis. Imaging can show patterns of joint change that differ from those of other conditions. NICE Clinical Knowledge Summaries tell people with psoriasis to seek urgent advice for unexplained joint pain or swelling.

There is no single test, so doctors look at the overall pattern. The table lists the features described by the NHS and Arthritis UK.

Arthritis UK says the chances of these complications are rare, but they are worth knowing about. Seek urgent medical attention if one or both eyes are red and painful, particularly with a change in vision, because this could be uveitis, which can permanently damage eyesight if left untreated. You could go to your GP, an eye hospital or A&E.

It says psoriatic arthritis can put you at a slightly higher risk of a heart condition, and that not smoking, keeping to a healthy weight, exercising regularly and eating a healthy diet can reduce the risk. There is an increased risk of Crohn's disease: see a doctor about blood in your poo, diarrhoea lasting more than seven days, regular stomach pain, fevers or unexplained weight loss, particularly if two or more occur and do not go away. Non-alcoholic fatty liver disease can also develop.

Arthritis UK says psoriatic arthritis will not affect your chances of having children. If you become pregnant unexpectedly, it advises talking to your rheumatology department as soon as possible.

It says methotrexate, leflunomide and retinoid tablets and creams must be avoided when trying to start a family, during pregnancy and when breastfeeding, and that there is growing evidence that some other drugs for psoriatic arthritis are safe in pregnancy. Keeping the arthritis under control matters, because a flare-up during pregnancy can be harmful for you and your baby.

Arthritis UK also notes that if you have either psoriasis or psoriatic arthritis you could pass on genes that may increase your children's risk, although this is difficult to predict.

Arthritis UK says there are no diets that can cure psoriatic arthritis, and that a healthy, balanced, nutritious diet low in fat, salt and sugar is good for overall health and heart health. It suggests talking to your doctor or a dietitian, or using the NHS Eatwell Guide, if you need more information.

The NHS suggests regular low-impact exercise such as swimming, walking and yoga to strengthen and protect your joints, losing weight if you are overweight to reduce pressure on the joints, cutting down on alcohol if you take medicines, not smoking because it can make symptoms worse, and avoiding herbal remedies that may interfere with your medicines.

The NHS says to see a GP if you have joint pain, stiffness and swelling that keeps coming back, even if you do not have psoriasis. NICE Clinical Knowledge Summaries advise people with psoriasis to seek urgent advice for unexplained joint pain or swelling, as it may be psoriatic arthritis that needs specialist rheumatology referral.

A red, painful eye with changes in vision needs urgent attention the same day, as described above. If you have bowel or liver symptoms, mention them to your rheumatology team rather than assuming they are unrelated.

On the NHS the route is usually your GP, then a referral to a rheumatologist. NICE guideline NG65 says people with suspected new-onset inflammatory arthritis should be referred urgently to a rheumatologist for a spondyloarthritis assessment, and that people with dactylitis should also be referred.

Arthritis UK says you are likely to see a team: a rheumatologist who is usually responsible for overall care, a specialist nurse to help monitor treatment, a dermatologist for the skin, and physiotherapists, occupational therapists and podiatrists as needed. Some people choose to see a rheumatologist privately; whichever route you take, regular blood tests and reviews continue alongside DMARDs and biologics.