Psoriatic Arthritis 

 

What is Psoriatic Arthritis (PsA)?

 Psoriatic arthritis is a chronic inflammatory disease that usually affects those that have Psoriasis. Psoriasis a skin condition causing a red, raised flaky rash that most commonly affects the knees, elbows and scalp. Around 10-20% of people with psoriasis go on to develop arthritis, although some patients develop arthritis before the psoriasis.

Inflammation is a response of the body to injury or infection. It is driven by the immune system. In PsA and psoriasis, cells from the immune system migrate to joints and the skin and become activated, which leads to inappropriate inflammation, skin changes and eventually joint damage. As the immune system cells appear to target healthy tissue, Psoriasis and PsA are known as autoimmune diseases.

 

Causes of Psoriatic Arthritis

As both psoriasis and psoriatic arthritis are autoimmune diseases, around 40% of patients with PsA have a first degree relative with either the skin or joint disease.

There is currently research looking into the role of triggers of developing PsA, such as the gut microbiome (bacteria in the gut), infections, trauma and stress.

Patients who are overweight or smoke are more likely to develop PsA.

PsA is associated with developing other autoimmune disorders

such as inflammatory bowel disease (Crohn’s colitis and Ulcerative colitis) as well as inflammatory eye disease such as uveitis.

Symptoms of Psoriatic Arthritis

• General symptoms
  • Fatigue
  • Weight loss
  • Low grade fever
  • Low mood

Psoriatic arthritis can involve the peripheral joints- joints in the arms or legs or the axial skeleton (spine), where it is part of the group of diseases called spondyloarthropathies.

Skin conditions:

• Psoriasis lesions, often missed if present on the scalp or in ear canals/ belly buttons
• Psoriatic nail changes- pitting, thickening and colour changes. Sometimes the nail can lift away from the finger

Peripheral joint pain, stiffness and swelling

• Joints are usually affected asymmetrically
• Stiffness is often worse in the morning and can last for an hour or longer
• Often involves the whole finger or toe, this is called dactylitis (sausage digit)
• Enthesitis is inflammation in the attachment of tendons to bones and often affects the back of the heel, knees and elbows.
• Arthritis mutilans is a severe form of joint destruction

Back symptoms- Spondylititis

• Stiffness and pain or restriction in movements of the spine and sacroiliac joints (joints between the spine and pelvis)

Other rarer symptoms

• eye inflammation- seek urgent medical attention of your eyes are red, painful or you have changes in your vision or difficultly looking at light
• Increased risk of heart problems such as heart attacks
• Inflammatory bowel disease- diarrhoea, abdominal pain and blood in your stool

Metabolic co-morbidities

• Obesity
• High cholesterol
• Non alcoholic fatty liver disease- build up of fat in the liver which if can result in liver cirrhosis
• Type 2 diabetes
• Metabolic syndrome
  • A combination of high blood pressure, high cholesterol, obesity and diabetes

How do we diagnose Psoriatic Arthritis?

As PsA is a seronegative disease (no antibodies present), therefore diagnosis is based on symptoms and examination.

Blood tests:

• PsA is most commonly classified as seronegative- therefore no antibodies are present such as:
  • anti-cyclic citrullinated protein antibodies (ACPA)
  • Rheumatoid Factor (RhF)
• Inflammation markers
  • CRP and ESR
• Full blood count
  • May show evidence of anaemia and raised platelets
• Lipids
  • Montoring of cholesterol to monitor heart disease risk
• Liver function tests
• Glucose- screening for diabetes

Imaging

• X-rays- these look for erosions of the bones and narrowing of the gaps between joints
• MRI scans- These scans are performed to look for evidence of inflammation that cannot be seen on examination. In particular they are the first line investigation to look for spinal disease
• Ultrasound scans- these can often be performing in clinic to see if inflammation is present in the peripheral joints

Treatment of Psoriatic Arthritis

Peripheral joints

The mainstay of treatment with Disease-modifying anti-rheumatic drugs (DMARDs).

• Methotrexate, Sulfasalazine, and Leflunamide
• Methotrexate can be effective for psoriasis too

During acute flares of the joints and whilst the DMARDs take effect we often prescribe a short course of steroids

Drugs such as painkillers may also be prescribed to help reduce the pain. These are good for relieving symptoms but have no effect on progression of the disease.

Biological DMARDs are prescribed as second line therapy if DMARDs fail to control inflammation.

Spondyloarthritis

Non steroidal anti-inflammatories are our first line treatment for back symptoms alone. Should these not improve symptoms or be contraindicated, biological DMARDs would be second line therapy.

 

Assessment of disease activity

PsARC- For peripheral joints

BASDAI- for spinal symptoms

BSA- body surface area of psoriasis

LES- Leeds enthesitis score (out of 6)

Useful Links

Versus Arthritis:  http://www.versusarthritis.org