Seronegative rheumatoid arthritis is one of two types of rheumatoid arthritis, an autoimmune condition that causes pain, swelling, and stiffness at the joints.

The other, and most common, kind of rheumatoid arthritis (RA) is seropositive RA.

Seronegative RA is the least common of the two types of RA and does not have the same markers that usually characterize the condition. These markers, which are found in the blood, are anti-cyclic citrullinated peptide (anti-CCP) antibodies or rheumatoid factor.

Rheumatoid factor is a protein produced by the immune system that can attack healthy tissue in the body. Because healthy people do not normally produce rheumatoid factor, the presence of this protein in the blood can indicate that a person may have an autoimmune disease.

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Stiff joints and joint pain in the morning may indicate the presence of rheumatoid factor.

As well as RA, conditions associated with rheumatoid factor include:

  • Sjögren's syndrome
  • Chronic infection
  • Scarring of the liver
  • Abnormal proteins in the blood
  • An inflammatory muscle disease called dermatomyositis
  • Inflammatory lung disease
  • Mixed connective tissue disease
  • Lupus
  • Cancer

Although it is very rare, some people without any medical problems produce a small amount of rheumatoid factor, but doctors do not yet understand why this happens.

A doctor may recommend a blood test to determine the presence of rheumatoid factor if a person has any of the following symptoms:

  • Stiffness of the joints
  • Joint pain in the morning
  • Nodules under the skin
  • Loss of cartilage
  • Warmth and swelling in the joints

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Seronegative RA may be diagnosed when the symptoms are symmetrical on both sides of the body.

To be diagnosed with seronegative RA, a person must experience symptoms including pain, tenderness, swelling, and redness of multiple joints.

The symptoms must also be symmetrical, which means that the symptoms appear in the same way on both sides of the body.

Other symptoms can include morning stiffness that lasts for longer than 30 minutes, fatigue, and redness of the eyes.

Some experts think that people with seropositive RA experience more severe symptoms than people with seronegative RA. However, some studies have found that there is little difference between the two types of RA in terms of how severe symptoms are.

Although blood tests can determine the presence of rheumatoid factor in a patient's blood, seronegative RA is difficult to diagnose. This is because there is a lack of the usual antibodies that indicate seropositive RA.

However, if someone exhibits strong symptoms usually associated with RA, such as the same joint pain on both sides of the body and inflammation in multiple joints, then a doctor may recommend an X-ray. X-ray results can show the doctor if there is the erosion and damage to the bone and cartilage that are typical symptoms of RA.

What other conditions are associated with seronegative RA?

People with RA are at increased risk of developing some other chronic conditions. These conditions include Sjögren's syndrome, psoriasis, Felty's syndrome, lupus, and anemia.

Non-steroidal anti-inflammatory drugs (NSAIDs) may be used to treat symptoms of seronegative RA during flare-ups, but they do not affect the course of the disease. Disease-modifying antirheumatic drugs (DMARDs), such as methotrexate, are often prescribed to begin with. Doctors often prescribe steroids as well to get the inflammation under control.

DMARDs restrict the immune system and help to preserve joints by blocking the inflammation that can slowly destroy the joint tissue in people with RA.

Before prescribing DMARDs, the doctor will take an X-ray and blood tests so that they can monitor both the severity of the patient's condition and any side effects over time.

It usually takes a couple of months for the effects of DMARDs to become noticeable. The doctor may prescribe NSAIDs or corticosteroids in the meantime to help with pain and inflammation.

If the DMARDs do not work for a person, a doctor may prescribe medications that work on the immune system in different ways. One example of this type of medication is rituximab, which works specifically on the B cells - one of the many parts of the immune system.

What impact does diet have?

The Arthritis Foundation suggest that eating certain foods may be helpful in managing the symptoms of RA. However, people who have RA should consult with their doctor before implementing any special diets.

The best diet for someone with RA should include lots of plant-based foods. About two-thirds of the diet should come from fruits, vegetables, and whole grains, which are all thought to help reduce inflammation. Lean sources of protein and low-fat dairy products should make up the other third of the diet.

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The Mediterranean diet has been recommended as a good diet for people with arthritis.

The anti-inflammatory properties of omega-3 fatty acids from fish oil have been found to ease pain and stiffness in tender joints. As a result, experts recommend including cold-water fish, such as herring, salmon, and tuna in the diet.

A person with RA should avoid omega-6 fatty acids from corn, safflower, soybean, and sunflower oils as they can increase the risk of joint inflammation and obesity.

Some foods that are associated with making inflammation worse include hamburgers, chicken, and meats that have been grilled or fried at high temperature.

Experts recommend the Mediterranean diet as a simple way for people with RA to achieve a healthful, well-balanced diet that includes the right amount of omega-3 fatty acids, fruits, vegetables, and whole grains.