An Overview of Psoriatic Arthritis

A form of arthritis integrally linked to psoriasis

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Psoriatic arthritis is an inflammatory form of arthritis integrally linked to the autoimmune disease psoriasis. Symptoms include joint pain and stiffness, the swelling of the fingers and toes, skin lesions, and nail deformity. Psoriatic arthritis can occur on its own but is usually preceded by psoriasis in around 85 percent of cases.

The causes of psoriatic arthritis are poorly understood but are believed to be the result of genetics and environmental factors. Treatment is primarily focused on the alleviation of inflammation using either oral or injected medications. Surgery is rarely needed.

Psoriatic arthritis affects around a million adults in the United States, with men and women affected equally. It is typically diagnosed between 30 and 50 but can occur at any age.

Symptoms

Psoriatic arthritis affects the joints as well as the skin and nails. Symptoms can vary from person to person but often include:

  • Pain, swelling, or stiffness in one or more joints
  • Joint redness and warmth
  •  Sausage-like swelling in the fingers or toes (known as dactylitis)
  • Pitting, thickening, crumbling, lifting, or discoloration of the nail plate (nail psoriasis)
  • Dry, red, scaly skin lesions (known as plaques)
  • Eye problems, including uveitis and conjunctivitis
  • Persistent and often extreme exhaustion

Psoriatic arthritis, like all other psoriatic diseases, is characterized by the spontaneous appearance or worsening of symptoms (known as flares), followed by periods of low disease activity or remission.

Psoriatic arthritis can develop in any joint of the body but is most common in the hands, feet, wrists, and lower back. If not treated immediately, psoriatic arthritis can lead to permanent joint damage and the loss of mobility and joint function.

Types

Psoriatic arthritis belongs to a group of joint disorders known as spondyloarthropathies. There are five types of psoriatic arthritis that are differentiated by their symptoms and location. Some of these characteristics can overlap or co-occur. Among them:

  • Symmetric psoriatic arthritis affects joints on both sides of the body (such as both knees or both hips) and often multiple joints (polyarthritis). It is similar to rheumatoid arthritis but is typically milder. Around 20 percent of people with psoriatic arthritis have this form of the disease.
  • Asymmetric psoriatic arthritis does not affect the same joints on both sides of the body. Generally considered a milder form of psoriatic arthritis, it may advance to symmetric disease if left untreated. The majority of people with psoriatic arthritis have this type.
  • Distal interphalangeal predominant (DIP) arthritis is considered the "classic" form of psoriatic arthritis even though it involves only 5 percent to 10 percent of cases. DIP arthritis primarily involves the distal joints (those closest to the nail) of the fingers and toes.
  • Spondyloarthritis primarily affects the spine. Between 5 percent and 20 percent of people with psoriatic arthritis will experience spinal involvement, typically around the sacrum (tailbone) and lower back.
  • Arthritis mutilans is a rare form of the disease that affects less than 5 percent of people with psoriatic arthritis. Arthritis mutilans is characterized by severe joint deformity, mainly in the hands, feet, and wrists but also in the lower back and spine.

Causes

Psoriatic arthritis is an autoimmune disease in which the immune system mistakenly attacks normal cells and tissues. Unlike rheumatoid arthritis, the attack is not direct but is rather the indirect consequence of psoriasis.

With psoriasis, the immune system will target skin cells called keratinocytes, causing chronic inflammation and the formation of skin plaques. Over the span of years or decades, the inflammation can "spill over" and affect other organ systems, including the joints, eyes, nails, brain, and kidney.

Even if the autoimmune inflammation doesn't manifest with skin symptoms, it can still affect the joints and lead to the eventual development of psoriatic arthritis.

Genetics and Environment

The causes of psoriatic arthritis are unclear. Most scientists believe that genetics predispose certain individuals to the disease, while environmental triggers effectively "switch on" disease symptoms. This is evidenced in part by the high rates of psoriatic diseases in families.

According to a 2010 review from the University of Toronto, you are 55 times more likely to get psoriatic arthritis if a first-degree relative (a parent or sibling) has the disease.

Genetic testing has further revealed the 40 percent to 50 percent of people with psoriatic arthritis have a genetic mutation, called HLA-B2, involving a protein that the body uses to target immune attacks.

Among some of the common triggers of psoriatic arthritis are:

  • Smoking
  • Stress
  • Excessive alcohol use (especially non-light beer)
  • Cold, dry weather
  • Certain drugs (including beta-blockers and lithium)
  • Skin infections (especially Staphylococcal aureus and Streptococcal epidermidis)

Diagnosis

Psoriatic arthritis is typically diagnosed and treated by a rheumatologist. There is no single test used to diagnose the disease. A physical exam and imaging studies can help identify characteristics of psoriatic arthritis, including joint erosion, skin plaques, nail deformity, and a family history of the disease.

Imaging modalities include X-ray, ultrasound, bone scans, and magnetic resonance imaging (MRI). With psoriatic arthritis, there will often be evidence of cortical bone thinning in which the outer surface of the bone will begin to wear away.

If skin lesions are present, a biopsy may be performed to obtain a tissue sample. Under the microscope, psoriatic skin cells will appear acanthotic (compressed), providing additional evidence of the disease.

Differential Diagnoses

The doctor may also take blood tests or joint fluid samples (arthrocentesis) to check whether the symptoms are caused by other diseases, such as rheumatoid arthritis, gout, reactive arthritis, ankylosing spondylitis, and osteoarthritis. This differential diagnosis is essential to confirming psoriatic arthritis as the cause.

With gout, for example, there will be uric acid crystal in the joint fluid sample. Meanwhile, blood tests can detect whether proteins called rheumatoid factor (RF) are present, suggesting rheumatoid arthritis as the cause.

Osteoarthritis is characterized by the absence of inflammation and, unlike psoriatic arthritis, will show no elevation of inflammatory markers in blood tests.

Treatment

Since psoriatic arthritis involves both the joints and skin, different treatments may be used for different symptoms. Your rheumatologist will determine the appropriate course of treatment based on the severity and location of your symptoms.

The primary aims of treatment are to temper the inflammation that drives the disease, to prevent disease progression, and to maintain joint function. Options include:

  • Nonsteroidal anti-inflammatory drugs (NSAIDs), including over-the-counter drugs like Advil (ibuprofen) and Aleve (naproxen) or prescription NSAIDs like Voltaren (diclofenac) and Celebrex (celecoxib).
  • Disease-modifying antirheumatic drugs (DMARDs) like methotrexate, cyclosporine, or Arava (leflunomide), which are taken orally and suppress the immune system as a whole
  • Biologic drugs like Enbrel (etanercept), Remicade (infliximab), Simponi (golimumab), and Cimzia (certolizumab pegol), which are delivered by injection and temper the immune response on the cellular level
  • Otezla (apremilast), an oral drug that prevents the breakdown of an enzyme called phosphodiesterase 4 (PDE4) that regulates inflammation

Many of these same medications are used to treat skin plaques in addition to topical corticosteroids, oral or topical retinoids, and ultraviolet (UV) light therapy.

Intra-articular corticosteroid injections, involving the injection of steroids into the joint space, are used with caution in people with psoriatic arthritis. While they can ease inflammation, they can make skin plaques worse and contribute to brittle bones.

Most people with psoriatic arthritis will never need surgery. If the joint impairment is severe, a synovectomy may be performed to remove the lining of the joint (called the synovium). If the damage is extensive and/or affects the quality of life, joint replacement surgery (arthroplasty) may be indicated.

Coping

Being proactive in your treatment and practicing self-care is important for people with psoriatic arthritis. In addition to taking medications as prescribed, there are things you can do to better cope with the disease:

  • Exercise regularly. Physical activity, such as walking and stretching daily, can help keep joints flexible and build supporting muscle around the joint. Focus on moderate-intensity, low-impact exercise routines performed at least thrice weekly. 
  • Lose weight. Excess weight places added stress on the joints. If you are carrying extra pounds, losing weight can not only improve your mobility but reduce the inflammatory burden that occurs when adipose (fat-storing) tissues accumulate
  • Manage your stress. Explore deep breathing exercises, meditation, yoga, tai chi, or guided imagery to reduce stress levels. If you are unable to cope, do not hesitate to ask your doctor for a referral to a therapist or psychiatrist.
  • Avoid flares. If you don't know what is causing your symptoms to flare, keep a journal to monitor when symptoms worsen. Provide details of what you were doing in the days preceding the flare, including medications you took, stresses you may have been under, or infections or injuries you may have incurred.

    A Word From Verywell

    Psoriatic arthritis is a painful, progressive illness, and, without proper treatment, could lead to a reduced quality of life and disability. If you think you may have psoriatic arthritis, speak to your doctor and start treatment as soon as possible.

    If you feel isolated or need support, reach out to family or friends. You can also search for online support groups on Facebook or join TalkPsoriasis, an interactive online community organized by the National Psoriasis Foundation.

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