Adults living with rheumatoid arthritis (RA) are generally classified as having seropositive or seronegative RA. Your RA diagnosis is based on the presence of biomarkers or proteins in your blood.

There are many other types of RA, categorized based on age and symptoms. Some people with other inflammatory diseases can develop overlapping RA. This article will explore the major types of RA, along with less common forms.

Seropositive Rheumatoid Arthritis

“Seropositive” is a medical term for having certain immune system proteins, called antibodies, in your blood. People with seropositive RA may have a few different antibodies.

Normally, your immune system makes antibodies to protect you from infections. People with autoimmune diseases make abnormal antibodies that attack healthy cells instead. RA can be characterized by two antibodies:

• Rheumatoid factor (RF)
• Anti-cyclic citrullinated peptide (anti-CCP) antibodies or anti-citrullinated protein antibodies (ACPAs)

People with seropositive RA have RF or anti-CCP antibodies — sometimes both — in their blood. The Arthritis Foundation notes that between 60 percent and 80 percent of people with RA have anti-CCP antibodies. Around 70 percent of people with RA also have RF. Health care providers use blood tests to measure these proteins and diagnose rheumatoid arthritis.

Anti-CCP antibodies are highly specific to RA, with studies showing a specificity of up to 98 percent. This means if you test positive for anti-CCP antibodies, there’s a high likelihood you have RA. Some people with RA produce these antibodies many years before they receive a formal diagnosis.

Most people who have anti-CCP antibodies also have rheumatoid factor. However, RF antibodies are less specific to RA. These proteins are found in people with other conditions or autoimmune diseases, including:

• Systemic lupus erythematosus
• Chronic (long-term) liver infections with viral hepatitis
• Sjögren’s syndrome
• Inflammatory lung diseases
• Cancer
• Connective tissue diseases, such as scleroderma

Seronegative Rheumatoid Arthritis

If you’re diagnosed with RA but don’t have RF or anti-CCP antibodies, you have seronegative RA. Doctors usually have a harder time diagnosing seronegative RA since it doesn’t have a biomarker. You may get misdiagnosed with another type of arthritis, such as:

• Gout
• Psoriatic arthritis (PsA)
• Spondyloarthritis

Researchers haven’t been able to determine which is more severe — seropositive or seronegative RA. One study of people with seronegative RA found they had more disease activity and inflammation compared to those with seropositive RA. However, other reports show that the two types progress similarly over time.

It’s also possible for someone initially diagnosed with seronegative disease to later develop markers for seropositive arthritis, changing their diagnosis. Additionally, many people initially diagnosed with seronegative RA may receive a different diagnosis years later. In one study of 10,000 people with seronegative RA, over 1,000 were diagnosed with PsA or spondyloarthritis years later.

These shifts highlight how autoimmune conditions can evolve over time. Rheumatological disorders exist on a continuum, with overlapping symptoms and markers that can change. Your specific diagnosis can depend greatly on what signs and test results are present when you first meet with your rheumatologist.

Juvenile Rheumatoid Arthritis

Did you know that RA can also develop in children and teenagers? Juvenile idiopathic arthritis (JIA) occurs in children ages 16 and younger. Doctors diagnose JIA when a child has pain and swelling in one or more joints for at least six weeks.

There are several types of JIA, each based on the child’s symptoms and number of joints affected. Many treatments for JIA are the same as those for adult RA, including:

• Corticosteroids or steroids
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Disease-modifying antirheumatic drugs (DMARDs)
• Biologics

It’s important that children with JIA get the right diagnosis and treatment plan as soon as possible. Early diagnosis and treatment can help prevent lasting joint damage and improve quality of life, providing better outcomes.

Oligoarticular JIA

Oligoarticular JIA affects up to four joints throughout the body, typically the elbows, knees, and ankles (large joints). This type of JIA is also associated with uveitis — inflammation in the uvea (middle layer of the eye).

Oligoarticular JIA is the most common type, affecting around half of children with juvenile RA. There’s a chance a child will outgrow the condition by the time they’re an adult.

Polyarticular JIA

Polyarticular JIA affects five or more joints within the first six months of the symptoms starting. The second most common type of JIA, it involves both large and small joints. Doctors can test children with polyarticular JIA for rheumatoid factor. The condition is divided into two groups — RF-positive and RF-negative.

Children with RF-positive polyarticular JIA are typically preteen and teenage girls, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases. This condition looks similar to RA in adults.

RF-negative disease is usually associated with uveitis and is more common in young girls. Doctors can also test for antinuclear antibodies, which are usually found in people with lupus and infections but can develop in RF-negative polyarticular JIA. However, having these antibodies doesn’t mean that a child with JIA will later develop lupus.

Psoriatic Arthritis

Some children and adults with rheumatoid arthritis have psoriasis, an inflammatory skin condition. A child who has psoriasis with RA symptoms may be diagnosed with psoriatic arthritis. Psoriasis causes dry, scaly, discolored patches of skin, sometimes covered in white or silvery dead skin cells.

The exact symptoms of PsA differ among children. Some may first develop swollen and painful joints, followed by rashes years later. Other children develop skin symptoms first. PsA can also cause swelling in fingers and toes and pitting in fingernails.

Enthesitis-Related JIA

Enthesitis refers to inflammation at the entheses — the sites where bones connect to tendons or ligaments. Children with enthesitis-related JIA have symptoms of both arthritis and enthesitis. Unlike other types of JIA, enthesitis-related JIA affects boys ages 7 years and older, according to Cleveland Clinic.

Commonly affected places include the knees, hips, and spine. Eye problems like uveitis can also occur.

Systemic Onset JIA

Children with systemic onset JIA have symptoms throughout the entire body. This condition usually includes inflammation and swelling in at least one joint and affects internal organs like the heart, liver, and immune system organs such as the spleen and lymph nodes.

Fevers and rashes are also common with systemic onset JIA. Rashes typically form on the arms, legs, and middle of the body, along with fevers. Uveitis and eye problems are rare. Systemic onset JIA is the most severe type and can be life-threatening if not recognized and treated promptly.

Other Types of Rheumatoid Arthritis and Related Conditions

Some people develop less common types of inflammatory arthritis or have RA alongside other autoimmune diseases.

Palindromic Rheumatism

Palindromic rheumatism causes random attacks of joint pain, inflammation, and swelling that can last for many hours or days. Symptoms develop suddenly and disappear without leaving any lasting joint damage.

People between ages 20 and 50 are most likely to develop palindromic rheumatism. Although doctors aren’t sure of the exact cause, they believe that it may involve the immune system, similar to RA. People with palindromic rheumatism also tend to have genetic risk factors similar to those seen in RA.

According to the Arthritis Foundation, around half of people with palindromic rheumatism go on to develop RA. Some researchers believe that palindromic rheumatism is a condition that forms before RA.

Rheumatoid Arthritis Overlap Syndrome

Some people with inflammatory diseases have distinct symptoms of other diseases. This is known as overlap syndrome.

For example, research shows that 32 percent of people with scleroderma also have RA. This connective tissue disease causes the skin to harden and tighten. The combination of rheumatoid arthritis and lupus is known as “rhupus syndrome.” Studies have found that rhupus syndrome is less common, affecting only up to 2 percent of people with rheumatic diseases. Some studies report even lower rates.

Doctors usually find it challenging to diagnose inflammatory and connective tissue diseases. The many shared symptoms can make it difficult to tell the conditions apart. If you think you may have overlap syndrome with RA and another condition, talk to your doctor. They’ll work with you to get the right diagnosis and help you find the best treatment plan to manage both conditions.

Talk With Others Who Understand

On myRAteam, the social network for people with RA and their loved ones, more than 206,000 members come together to ask questions, give advice, and share their stories with others who understand life with rheumatoid arthritis.

Have you been diagnosed with seronegative or seropositive RA? Do you have another, rare type of RA? Share your experience in the comments below, or start a conversation by posting on your Activities page.