Psoriatic arthritis (PsA) and psoriasis are both autoimmune diseases, meaning they result from the immune system mistakenly attacking the body’s own healthy tissues. In psoriasis, the immune system primarily attacks the skin. In psoriatic arthritis, it primarily attacks the joints. Inflammation caused by the body’s overactive immune response leads to the symptoms characteristic of psoriasis and PsA.

Psoriasis and PsA share genetic similarities and are considered common comorbidities, conditions that can occur simultaneously. In fact, about one-third of people with psoriasis will eventually develop PsA. However, they are distinct conditions that can stand alone. Psoriatic arthritis can develop years before psoriasis symptoms appear, or it may develop without psoriasis symptoms at all.

About Psoriatic Arthritis and Psoriasis

Psoriasis is a chronic, inflammatory disease that typically affects the skin. In about 80 percent of cases, psoriasis manifests as a scaly, itchy rash of skin plaques that most frequently affects the elbows, knees, and scalp.

PsA is characterized by inflammation of the tendons and ligaments. Symptoms of psoriatic arthritis include lower back pain, inflammatory joint pain, and joint swelling and stiffness. Often, psoriatic arthritis also affects the nails, causing nail changes and symptoms such as pitting — small dents in your nails. Left untreated, PsA can cause lasting joint damage. Approximately 1 in 5 people with PsA will experience spinal inflammation, known as psoriatic spondylitis. In some instances, spinal inflammation is so severe, it can cause complete fusion of the vertebrae, known as ankylosing spondylitis.

The Relationship Between Psoriatic Arthritis and Psoriasis

Psoriasis is a risk factor for PsA. Approximately 30 percent of people with chronic psoriasis develop PsA. Around 15 percent of people with PsA have no history of psoriasis before the onset of arthritis. The two are distinct chronic conditions, though they share a genetic connection. Psoriasis is an inflammatory and autoimmune skin disease. PsA is an inflammatory form of rheumatic disease or inflammatory arthritis.

The majority of PsA diagnoses are made in people who already have psoriasis. PsA usually starts 10 to 20 years after the onset of psoriasis. However, a person can develop PsA at any age, whether or not they have developed psoriasis. A MyPsoriasisTeam member shared, “I've suffered with psoriatic arthritis for as long as I've had psoriasis: 30 years (since I was 13 years old).”

But the two conditions do not always occur together. “Everyone seems to have psoriasis along with psoriatic arthritis,” another MyPsoriasisTeam member said. “I just have psoriatic arthritis.”

Diagnosing PsA Without Psoriasis: Difficult but Doable

Diagnosing PsA, especially in the absence of psoriasis, can be challenging. This contributes to delayed diagnosis and misdiagnosis. This difficulty stems from the fact that symptoms of PsA are similar to those of diseases such as rheumatoid arthritis, osteoarthritis, and gout. Diagnosing PsA early and treating it promptly are important steps in helping prevent long-term, irreversible joint damage.

There is also a chance that a person diagnosed with either PsA or psoriasis actually has both conditions — but that one has gone undiagnosed or been misdiagnosed. A study published in the Journal of the American Academy of Dermatology found that approximately 15 percent of people with psoriasis had PsA that had gone unrecognized or undiagnosed.

There aren't any definitive tests, such as blood tests, to diagnose PsA. However, doctors can make a PsA diagnosis based on clinical signs and symptoms and by obtaining a medical history. The doctor will likely ask if you or a family member have previously had a psoriatic disease like PsA or psoriasis. This factor can significantly increase your risk of developing PsA — 40 percent of people with psoriatic arthritis have a family history of psoriatic disease.

Talk With Others Who Understand

MyPsoriasisTeam is the social network for people with psoriatic disease and their loved ones. More than 94,000 members come together to ask questions, give advice, and share their experiences of life with psoriasis or PsA.

Do you have psoriasis or PsA or both? Which came first? Leave a comment below or start a discussion on MyPsoriasisTeam.