Psoriatic arthritis and psoriasis are types of psoriatic disease. Psoriatic arthritis causes joint pain and stiffness, and psoriasis mainly involves the skin, but they often occur together.

An estimated 10–30 percent of people with psoriasis will develop psoriatic arthritis.

Both conditions are long-term and can get worse over time, though treatments can relieve the symptoms and slow down disease progression.

This article explores the link between psoriasis and psoriatic arthritis. It also looks at the causes, symptoms, and treatments of each condition.

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Genetics contribute to both psoriasis and psoriatic arthritis.

Psoriasis and psoriatic arthritis are related, but they are separate conditions.

Psoriasis causes skin cells to renew too quickly, resulting in a red, scaly rash on the skin and characteristic silvery plaques.

Psoriatic arthritis causes inflammation in the joints. This makes the joints feel stiff, swollen, and achy, and it may cause long-term damage to them. Psoriatic arthritis may affect one or multiple joints.

Though the diseases are related, psoriasis and psoriatic arthritis do not necessarily predict one another. Many people with psoriasis will never develop psoriatic arthritis, while some people have psoriatic arthritis without having psoriasis.

The severity of psoriasis also does not predict whether someone will develop psoriatic arthritis.

Still, the two conditions have links and similarities. Immune responses that lead to inflammation in the body cause the symptoms of both conditions. This inflammation causes the rash or joint pain.

Psoriasis can be very uncomfortable, and nearly 60 percent of people with the condition say that it interferes with their daily lives. Some people find that the symptoms of psoriasis affect their mental health and self-esteem.

Psoriatic arthritis can also cause debilitating and permanent damage to joints, even if it does not cause skin symptoms.

Doctors can prescribe effective treatments to help control the immune reaction and inflammation from psoriasis and psoriatic arthritis. With the right treatment, people with psoriatic disease can carry on with normal daily activities.

The symptoms of both psoriasis and psoriatic arthritis arise when the body's immune system malfunctions, leading to inflammation.

In psoriasis, the faulty reaction causes skin cells to grow too fast, promoting a buildup of skin cells on the surface. These cells appear as a scaly rash.

In psoriatic arthritis, the inflammation affects the joints. Permanent damage can result if the person does not seek treatment.

Doctors do not yet know the exact causes of psoriasis and psoriatic arthritis. However, they do know that genetics contribute to both conditions.

An estimated 1 out of 3 people with psoriasis say that they have a family member with psoriasis. Also, around 40 percent of people with psoriatic arthritis have a family member with psoriatic disease.

Still, many people have genes for psoriatic disease and never develop it. To develop psoriatic disease, a person must have the specific genes for it, as well as a "trigger" that activates it.

Possible triggers for psoriatic disease include:

  • an infection, such as strep throat or a cold
  • stress
  • an injury to the skin, such as a cut, bug bite, or sunburn
  • getting a tattoo or piercing
  • certain medications
  • cold weather
  • dry indoor air
  • use of tobacco or smoking
  • heavy alcohol use

These triggers may bring on psoriasis, and they can also cause flares. Flares are cycles during which symptoms become worse. Triggers vary from person to person and may change over time.

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Plaque psoriasis is the most common type of psoriasis.

Psoriasis and psoriatic arthritis symptoms often come and go in cycles. They may get worse during a flare and then improve. Symptoms may also move around, affecting different areas of the body at different times.

There are five main types of psoriasis, each with its own type of rash or set of skin changes:

  • Plaque psoriasis. This is the most common type. It causes raised red patches with a silvery white covering called plaques. It often affects the scalp, elbows, knees, lower back, and nails.
  • Guttate psoriasis. This is the second most common type. It causes small red dots on the skin. Strep infections can trigger guttate psoriasis, which often affects children or young adults.
  • Inverse psoriasis. This type causes a very red, smooth, shiny rash in areas where the skin naturally folds, such as the groin and armpit.
  • Pustular psoriasis. This causes red blisters with white pus, often on the hands and feet. The blisters are not contagious or infected.
  • Erythrodermic psoriasis. This is the rarest and most severe type. It causes a very red, fiery rash over a large part of the body. It can affect people who have plaque psoriasis that is not well-controlled.

Psoriatic arthritis is different from other forms of arthritis. It has two unique signs that doctors often use to help diagnose the condition:

  • Enthesitis. This occurs when sore or tender spots appear in areas where tendons or ligaments join onto the bones. This includes areas such as the back of the heel, the bottoms of the feet, elbows, ribs, the spine, and the pelvic area.
  • Dactylitis. This occurs when an entire finger or toe appears very swollen or sausage-like. This may affect one or multiple digits.

Other signs and symptoms of psoriatic arthritis include:

  • spondylitis, which is stiffness or pain in the back or neck that makes it difficult to bend or move the back
  • fatigue
  • feeling very tired and stiff in the morning
  • tendons that are painful, sore, or swollen
  • throbbing, stiffness, swelling, or pain in one or more joints
  • fingernails or toenails that separate from the nail bed or have tiny holes
  • sore or red eyes that resemble pink eye

A doctor may diagnose psoriasis simply by examining the skin and discussing symptoms and family history.

They may take a sample of skin, or a biopsy, and look at it under a microscope. There are no blood tests or other laboratory tests to check for psoriasis.

To diagnose psoriatic arthritis, a doctor may review a person's symptoms and family history. They will also likely check for distinctive signs of psoriatic arthritis, including enthesitis and dactylitis.

The doctor may order tests such as X-rays, MRI, or ultrasounds to look at the joints. They may use a blood test to rule out other forms of arthritis or other medical conditions that can cause joint pain.

A doctor can help a person choose medications and treatments for psoriatic disease based on how severe the symptoms are. No single treatment works for everyone.

Treatment for symptoms

Some possible treatments for the symptoms of psoriasis and psoriatic arthritis include:

  • Over-the-counter medication. Pain relievers and anti-inflammatories can relieve mild, occasional psoriatic arthritis pain.
  • Salicylic acid or coal tar. Creams, shampoos, and washes that contain salicylic acid or coal tar may help remove scales and relieve itching and inflammation in some people.
  • Topical creams. Prescription topical creams can help slow down skin cell turnover and lower inflammation, reducing skin symptoms.
  • Light therapy. A doctor may prescribe phototherapy, or light therapy, which uses ultraviolet light to help clear up psoriasis scales. Tanning beds are not effective or safe for this purpose.
  • Corticosteroid injections. Injections of corticosteroid solutions can relieve inflammation and swelling in joints.

Long-term treatment

The following drugs target the underlying processes that lead to psoriatic disease.

The choice will depend on whether the person has joint inflammation, skin involvement, or both. If the individual only has skin symptoms, the doctor will consider what type of psoriasis it is and consider the symptom severity.

  • Biologic drugs. In 2018, new guidelines for treating psoriatic arthritis recommended biologic drugs for most people with a new diagnosis. In 2019, guidelines for treating psoriasis recommended the use of biologics, depending on the type and severity of symptoms. Biologics can cause adverse effects, and they are not suitable for everyone. A doctor can help an individual decide on the best treatment for them.
  • Systemic drugs: If a person cannot use biologic therapy, a doctor may recommend a systemic medication known as an oral small molecule (OSM), such as apremilast (Otezla) or tofacitinib (Xeljanz).
  • Disease-modifying antirheumatic drugs (DMARDs): DMARDs include various systemic medications that can help prevent inflammation and further joint damage in psoriatic arthritis.

In some cases, people with psoriatic arthritis may benefit from surgery to repair or replace damaged joints.

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Doctors may advise keeping a journal of symptoms and triggers to help control flares.

People can control psoriasis and psoriatic arthritis flares by taking medications as prescribed and working to avoid triggers.

A person's triggers can change over time. People can keep track of their triggers by keeping a journal of the dates and details of their symptoms, along with possible triggers. These may include:

  • illnesses
  • skin cuts and injuries
  • stressful events
  • medications

Some triggers, such as catching a virus, are more difficult to avoid.

Smoking increases a person's risk of developing psoriasis and can make its symptoms worse. A doctor can provide help for quitting. Nicotine replacements may be helpful, but patches may not be appropriate for people with skin conditions such as psoriasis.

Reducing or eliminating alcohol use can also relieve the symptoms of psoriasis. Heavy alcohol use can make psoriasis flares worse and may interfere with how some medications work.

Both psoriasis and psoriatic arthritis can have negative effects on people's physical and mental health. Taking medications as prescribed and avoiding triggers can significantly improve a person's quality of life and outlook.

With the number of effective treatment options currently available, many people with psoriatic disease can lead full, healthy lives.