Psoriatic arthritis

What is psoriatic arthritis?

Psoriatic arthritis is a condition that causes inflammation of the joints, making them stiff, painful and swollen, occurring in people who have psoriasis. Psoriasis can cause joint damage and approximately 15% of affected people will go on to develop psoriatic arthritis.Psoriatic arthritis usually develops between the ages of 30-50, but can also occur as early as childhood.

Psoriatic arthritis in the foot causes swelling and stiffness of the joints. 

Causes

Autoimmune response

Psoriatic arthritis is an autoimmune diseases, meaning that it is caused by the immune system mistakenly attacking healthy cells. It cannot be passed on from one person to another.

More specifically, psoriatic arthritis occurs when white blood cells produce several damaging chemicals in the skin and joints, as if fighting an infection or healing a wound. In turn, this immune response is thought to cause inflammation at the site where the tendon connects to the joint, and in the lining around the joint. Over time, the dual effect of inflamed tendon insertions and the lining of the joint, causes the breakdown of neighboring cartilage and bone. The end result can be rubbing of bone against bone.

Psoriatic arthritis causes thinning of cartilage and breakdown of bone. 

Genetic

Four genes have been identified as being important in the development of psoriasis - these are PSOR1, PSOR2, PSOR3 and PSOR4. Changes or variations in these genes are not only linked to psoriasis, but also to other autoimmune conditions including type 1 diabetes, Graves' disease, coeliac disease and rheumatoid arthritis. As psoriasis tends to run in families, it may be that one or more of these genes may be passed down from parents to children.

Also, a genetic marker called HLA-B27 is linked to psoriatic arthritis, as well as other autoimmune diseases. However, the exact role of this genetic link is unknown, as many people carry the marker without developing psoriatic arthritis.

Environmental

It is thought that a virus or other factors in the environment may play a role in triggering the immune response that causes inflammation of the joints. Sometimes psoriatic arthritis can follow an injury or accident that affects one or more joints.

Types

Psoriatic arthritis tends to fall into one of five main types depending on the location of symptoms.

Asymmetric arthritis

Asymmetric arthritis is where less than five joints are affected at any one time. Inflammation and swelling in the fingers and toes can cause them to look like sausages.

Symmetric arthritis

This type of psoriatic arthritis usually affects the same joints on both sides of the body in pairs. Also more joints are affected than in asymmetric arthritis. Symmetric arthritis may resemble rheumatoid arthritis in many ways, but with milder symptoms.

Spondylitis

Spondylitis means inflammation of the joints and discs in the spine, which leads to stiffness in the neck or lower back and trouble with movement. This condition only occurs in a small number of people and is more common in men than in women.

Distal interphalangeal predominant

The distal interphalangeal predominant (DIP) form of psoriatic arthritis affects the fingers and toes in the small joints closest to the nails. Skin and nail changes may also accompany the symptoms of arthritis. Again, this condition is quite rare and is more common in men than in women.

Arthritis mutilans

This rare type of psoriatic arthritis causes the small bones in the hands to wear away over time, resulting in permanent deformity and disability. Some people with the condition may also experience neck or lower back pain.

Signs and symptoms

Psoriatic arthritis generally develops about 10 years after the appearance of psoriasis. It may be mild and involve only a few joints, or it may be severe and affect multiple joints, including those of the spine. The most common symptoms are:

• Joint pain and swelling;
• Joint stiffness, particularly in the morning or after rest;
• Swollen fingers or toes;
• A reduced range of motion in the joints and limbs;
• Inflamed tendons and ligaments, particularly in the heel or sole of the foot;
• Nail changes, such as thickening, discoloration, pitting or lifting from the nail bed;
• Inflammation of other areas, such as the eyelid or eyelid lining;
• Mouth ulcers, and;
• Tiredness.

Although most common in adults, psoriatic arthritis can also occur in children - this is called juvenile psoriatic arthritis. Children with the condition usually develop symptoms around the age of 10 years.

In general, children have many of the same symptoms as adults, but their skin and joint problems are more likely to occur together. Although symptoms are usually mild, some children may experience severe or disabling problems into adulthood. For example, as the bones are still developing, juvenile psoriatic arthritis can permanently impair growth.

Methods for diagnosis

A doctor will diagnose psoriatic arthritis by looking for swollen and painful joints and asking questions about personal and family medical history. The skin, nails and scalp will also be examined, particularly if underlying psoriasis is yet to be identified. A small skin sample, called a biopsy, may also be taken.

While there is no specific test for psoriasis, blood tests or X-rays may be performed to look for signs of inflammation, or to rule out other types of arthritis. For example, most people with rheumatoid arthritis have an antibody in their blood that will not be present in those with psoriatic arthritis. Because of this, a blood test can be used to tell the conditions apart.

Once psoriatic arthritis is suspected, a referral is usually made to specialist doctor, also known as a rheumatologist. Over time, the rheumatologist will usually be able to make a firm diagnosis based on the pattern of symptoms.

Types of treatment

As there is no cure for psoriatic arthritis, treatments aim to reduce joint pain and swelling, prevent further damage to the joints and minimize disability. To achieve these goals, a combination of self-care, medications or even surgery may be prescribed.

It is also likely that treatment will come from more than one type of healthcare professional. This could include appointments with a doctor, rheumatologist, dermatologist, nurse, physiotherapist, occupational therapist or psychologist.

Self care

In consultation with a doctor or physiotherapist, it may be helpful to establish a gentle exercise routine to strengthen muscles and maintain joint flexibility. Low-impact options include walking, swimming and bike riding. A healthy eating plan incorporating fruit, vegetables and whole grains may also be recommended to help maintain a healthy weight, as being overweight can put extra stress on joints already damaged by psoriatic arthritis.

A doctor or occupational therapist may be able to suggest some practical advice for doing daily tasks in ways that protect affected joints. Some examples include using grabbing tools to pick up items in hard-to-reach places, splints for supporting the joints, or techniques for lifting heavy items.

For general symptoms of pain, swelling and tiredness, a doctor may suggest using cold packs to numb the area, applying heat to relax tight muscles, or rest and relaxation.

Medications

Non-steroidal anti-inflammatory drugs (NSAIDs)

As the name suggests, these medications reduce inflammation, pain and stiffness. Ibuprofen is an example of a tablet that is available from a pharmacy. Stronger NSAIDs are available by prescription only, as they are more likely to cause side-effects.

Corticosteroids

Corticosteroids also reduce swelling, pain and stiffness, but are not prescribed for psoriatic arthritis very often as they can cause a flare-up of psoriasis symptoms when treatment is stopped. Prednisolone is an example of a corticosteroid that is given in tablet form, usually when a previous treatment has not been effective. However, corticosteroids can also be injected into a muscle or joint to provide relief that can last for weeks or even several months.

Disease-modifying anti-rheumatic drugs (DMARDs)

The DMARD family of medications can help to slow the progression of psoriatic arthritis by preventing joint damage caused by the immune system. As these medications can prevent damage to the joints, they tend to be more effective when prescribed in the early stages of psoriatic arthritis.

Some examples of DMARD medications for psoriatic arthritis include methotrexate, leflunomide and sulfasalazine. These medications can take up to six months to start working and they do not directly reduce pain or inflammation. More than one DMARD may need to be trialed to find an effective option with acceptable side-effects.

Biological therapies

Another family of medications, known as biological therapies, may be suggested if treatment with DMARDs is not an option, or when two or more DMARDs have not worked. Some examples of biological therapies include adalimumab, etanercept and infliximab injections.

Surgery

When a joint becomes severely damaged, a doctor may recommend replacing it with an artificial one made from metal and plastic. Hips and knees are replaced most often, but shoulders, fingers, ankles and elbows can also be replaced. Surgery is also sometimes recommended for repairing damaged tendons. However, these options are only carried out in a small number of cases of psoriatic arthritis.

Potential complications

Osteoporosis

Having psoriatic arthritis increases the risk of developing osteoporosis. This link is strongest for the spondylitis subtype of psoriatic arthritis. Osteoporosis causes the bones to become thin and brittle, increasing the chance of a fracture.

Psychological effects

In some people, psoriatic arthritis may affect their ability to work and carry out daily activities. This may affect quality of life or cause psychological effects, such as distress, low self-esteem or depression.

Prognosis

Psoriatic arthritis varies from person to person, but the condition can usually be well managed with medication and self-care measures. It is common for symptoms to flare up and then settle for periods of time. However, complete remission is uncommon, with most people displaying some symptoms of arthritis for life. Ongoing treatment to control symptoms and prevent further joint damage is common.

In general though, treatment options have improved for psoriatic arthritis in recent times and the overall outlook is often good when the condition is diagnosed early.

Prevention

While development of psoriatic arthritis cannot be prevented, steps may be taken to help reduce joint pain and swelling, minimizing further damage to the joints and improving everyday functionality. A doctor will be able to suggest an appropriate combination of medication and self care options.