What is psoriatic arthritis?

What happens in psoriatic Arthritis?

What causes psoriatic arthritis?

What parts of the body are affected by psoriatic arthritis?

What are the signs and symptoms of psoriatic arthritis?

How is psoriatic arthritis diagnosed?

How is psoriatic arthritis treated?

PsO Let's Talk Psoriasis - Episode 4 (understanding psoriatic arthritis) video

Download our Living with psoriatic arthritis booklet

What is psoriatic arthritis?

Psoriatic arthritis (PsA) is an autoimmune disease - a form of inflammatory arthritis that can cause pain, swelling and sometimes damage to any joint in the body. It is a rarer form of arthritis compared to other forms of the disease (Osteoarthritis and Rheumatoid Arthritis).

About 1 in 50 people have psoriasis and up to one-third of them may develop PsA (note that prevalence rates and figures vary considerably), so having psoriasis does not automatically mean you will have PsA. In fact, most people with psoriasis never develop it.

Although PsA generally occurs after psoriasis develops there are cases where the arthritis develops first. PsA usually begins slowly spreading to other joints over a period of a few weeks or even months. In rare instances PsA can develop quickly and can be quite severe. It is an unusual arthritis because it can look very different from person to person.

Back to top

How has psoriatic arthritis affected your life? Share your experiences in this short survey.

What happens in psoriatic arthritis?

To explain what happens in PsA it helps to understand how both arthritis and psoriasis can affect the body.

A healthy immune system releases antibodies – agents that act as natural defences against injury or disease that heal the body in times of distress. Sometimes however an autoimmune disease occurs and turns the body against its own tissues. Psoriasis is an autoimmune disease that occurs when the immune system becomes confused and decides to “attack” the skin. It leads to a condition that causes a red, scaly rash, especially on the elbows, knees, back, buttocks and scalp. However, some people develop PsA before the condition while others will never develop the skin condition.

PsA is a type of inflammatory arthritis and an autoimmune disease. When it occurs, the joints become the target of the PsA attack.

Back to top

What causes psoriatic arthritis?

At present the exact cause is not known. Research has shown that a particular combination of genes makes some people more likely to get psoriasis and PsA. However, having genes that predispose you to PsA does not necessarily mean you will develop this disease. Some people think that an event has to occur to trigger it. Unfortunately, we don’t know what that “trigger” is. It could be a viral infection, trauma or something else in the environment. There may be more than one trigger.

Back to top

Which parts of the body are affected?

Any of the 78 joints in the body can be affected by PsA but some are more likely to be affected than others. These are outlined in the diagram below:

PsA also affects the body in certain patterns. They have been categorised into 5 different groups:

  1. Asymmetric Pattern This is the mildest form where PsA affects 1-3 joints on different sides of the body.
  2. Symmetric Pattern PsA involves many more joints and looks very much like rheumatoid arthritis.
  3. Distal pattern PsA affects the small joints in the fingers and toes closest to the nail.
  4. Spinal Pattern PsA affects the spinal column and may cause inflammation and stiffness in the neck, lower back, spinal vertebrae, or sacroiliac region (pelvic area), making motion difficult.
  5. Destructive Pattern PsA is a severe, painful deforming type of arthritis. It primarily affects the small joints in the fingers and toes closest to the nail leading to lost function of the involved joints. It also is frequently associated with lower back and neck pain. This pattern is very rare and is also known as arthritis mutilans.

While it is most commonly associated with joints, psoriatic arthritis is a systemic condition, meaning that over time the inflammation that characterises it can affect multiple joints and even organs.

Back to top

Early signs and symptoms of psoriatic arthritis

As with other forms of arthritis, the symptoms of PsA vary among different people. Many symptoms are common to other forms of arthritis, making the disease tricky to diagnose. Here’s a look at the most common symptoms – and the other conditions that share them

■ A red scaly skin rash.

■ Thickening, discoloration and pitting of the nails.

■ Stiff, painful, swollen joints. PsA typically affects the ankle, knees, toes and lower back. The joints at the tips of the fingers may also swell confusing it with gout, a form of inflammatory arthritis that typically affects only one joint.

■ Dactylitis: This is a sausage- like swelling of the fingers or toes. This symptom is one that often helps differentiate PsA from RA, in which the swelling is usually confined to a single joint.

■ Enthesitis: People with PsA often develop tenderness or pain where tendons or ligaments attach to bones. This commonly occurs at the heel (Achilles tendinitis) or the bottom of the foot (plantar fasciitis), but it can also occur in the elbow (tennis elbow). Each of these conditions could just as easily result from sports injuries or overuse as from PsA.

 ■ Pain and swelling at the back of the heel.

■ Eye inflammation (less frequent).

Back to top

How is psoriatic arthritis diagnosed?

There is no single test for psoriatic arthritis, but the diagnosis is based on your symptoms and a physical examination. It is easier to diagnose if you have psoriasis along with red swollen fingers or toes. Psoriasis and PsA occur more frequently in some families than in others so your doctor may ask about your family’s medical history.

Sometimes the doctor may make a diagnosis by eliminating other conditions with similar symptoms. He may therefore take a sample from the joint to rule out the presence of gout crystals.

Some of the symptoms of PsA are also similar to other forms of arthritis and it can sometimes be difficult to distinguish between psoriatic arthritis and rheumatoid arthritis (RA). Your doctor may therefore take a blood test for rheumatoid factor to eliminate the possibility of RA. If several joints are affected, your doctor will consider features such as the pattern of the arthritis – that is, which joints are affected. Your doctor may also send you for x-rays, MRIs and blood tests to rule out these conditions.

Establishing an accurate diagnosis is very important because there are many treatment options to manage the symptoms of PsA.

Back to top

How is psoriatic arthritis treated?

The importance of early intervention

PsA causes inflammation (swelling, pain and warmth) in the affected joints.

PsA can cause permanent joint damage quickly when it is not treated and controlled. This damage can even occur when the pain is not severe. Once damage occurs, it is not reversible and can cause significant pain and disability. Research has confirmed that treating PsA early and aggressively often improves the long-term outcome and significantly reduces damage. Early intervention and timely treatment therefore is critical to control the condition.

Once your diagnosis is confirmed, there are many treatments that can help decrease your pain and increase your movement. Non-medication therapies such as physiotherapy, occupational therapy, education, physical activity and relaxation techniques can all be helpful in the treatment of PsA.


The process of inflammation is similar in the skin and joints, so treatment aimed at one aspect of the condition often helps the other as well. The general approach to treating PsA is to reduce joint inflammation and prevent long-term damage to the joints.

The cornerstone of therapy is Disease Modifying Anti-Rheumatic Drugs (DMARDS). They are often used in combination with Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) and /or Corticosteroids (steroids). Although NSAIDs and steroids slow down the day-to-day inflammation, they don’t affect the long-term outcome of the disease.

A newer class of medication called biologics has revolutionised the treatment of PsA. These medications, which can be used in combination with DMARDs, also suppress inflammation and help prevent damage to the joint.

Disease-modifying anti-rheumatic drugs (DMARDs)

Disease-modifying drugs (DMARDs) tackle the causes of inflammation (pain swelling and stiffness) in the joints. DMARDs are important because they help prevent damage to the joint.

Your doctor will recommend a therapy that is best suited to your type and stage of arthritis, other medical problems and medications. Sometimes these drugs are given by injection.

Taking any medication carries some risk, which must be balanced against the potential benefits. It is important to recognise that the risk of joint damage and permanent disability is much greater than the risk of side effects from DMARDs to control the disease. When properly monitored, the vast majority of side effects are rare, and most are reversible by adjusting the dose or switching medications.

Phosphodiesterase 4 inhibitors

This newer therapy offers a treatment option for people who cannot use DMARDs or when one of these type of medicines did not work.  It works by reducing the activity of an enzyme in the body called ‘phosphodiesterase 4’ which is involved in the process of inflammation. Apremilast (Otezla®) is one such medication.

Biologic Therapies

Biologic therapies are a newer group of disease-modifying drugs that may be used if other DMARDs aren’t working well enough. These are given either by injection or through a drip into a vein.

This also includes a category of medicines called biosimilars. These drugs are follow-on versions of original biological medicines. They are independently developed after the patent protecting the original product has expired. Biosimilar medicines are intended to have the same mechanism of action as the original biological medicines and are designed to treat the same diseases as the innovator’s product. Two biosimilars are currently available in Ireland for PsA - Inflectra™ and Remsima™.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Non-steroidal anti-inflammatory drugs (NSAIDs) are a class of medications used to treat the pain and inflammation of arthritis. They act by blocking the inflammation that occurs in the lining of your joints. They can be very effective in controlling pain and stiffness.

Steroid Injections

Steroid tablets aren't generally used for psoriatic arthritis. However, your doctor might recommend steroid injections if your joints are particularly painful or your ligaments and tendons have become inflamed.

Skin Treatments

Your skin will usually be treated with ointments. There are five main types;

1. Tar-based ointments

2. Dithranol-based ointments (it's very important not to let these come into contact with normal skin)

3. Steroid-based creams and lotions

4. Vitamin D-like ointments such as calcipotriol and tacalcitol 

5. Vitamin A-like (retinoid) gels such as tazarotene

Properly caring for your skin will help you manage your symptoms. If you have severe psoriasis you should see a dermatologist.

Other treatments

If the creams and ointments don't help your psoriasis, your doctor may suggest the following;

a. Light therapy - short spells of exposure to high-intensity ultraviolet light

b. Retinoid tablets

Note that many of the DMARDs used for psoriatic arthritis will also help your skin condition. Similarly, some of the treatments for your skin may help your arthritis.

Treatments for nail psoriasis are usually less effective than the skin treatments. Many people use nail varnish to make the marks less noticeable.

PsO Let's Talk Psoriasis - Episode 4 (Understanding Psoriatic Arthritis)

Experts Prof. Doug Veale, Consultant Rheumatologist at St Vincent’s University Hospital and Grainne O’Leary, Chief Executive, Arthritis Ireland, provide a clear explanation of the condition and the supports available for people living with it. They are joined by Irish Paralympian Eamonn Byrne who talks about how he has learned to manage his psoriatic arthritis and the challenges he has faced. The panel tackle some of the most asked questions by people living with psoriatic arthritis as well as setting the record straight by busting some myths.

This series of videos was created by Janssen Sciences Ireland UC

Download our Living with psoriatic arthritis booklet

Back to top

For more detailed information about psoriatic arthritis and sleep & fatigue, exercise, work and lifestyle information, contact the Arthritis Ireland Helpline on 0818252846 [email protected] 

Sign-up for news and updates about PsA and Arthritis Ireland  Donate