Lupus and rheumatoid arthritis (RA) are both autoimmune diseases. In fact, the two diseases are sometimes confused because they share many symptoms.

Autoimmune disease occurs when your immune system attacks cells in your body, triggering inflammation and damaging healthy tissue. Scientists aren’t sure of all the triggers of autoimmune diseases, but they can run in families.

Women are at greater risk of having an autoimmune disease than men. African-American, Native-American, and Hispanic women are at even greater risk, according to the National Institutes of Health.

The most obvious similarity between RA and lupus is joint pain. Joint swelling is another common symptom, though the levels of inflammation can vary. Both diseases can cause your joints to become hot and tender, but this is more pronounced in RA.

Lupus and RA affect your energy levels as well. If you have either disease, you might feel constant fatigue or weakness. Having a periodic fever is another symptom of both lupus and RA, but it’s more common with lupus.

Both diseases are more common in women than in men.

There are many differences between lupus and RA. For instance, lupus might affect your joints, but it’s more likely to affect your internal organs and your skin than RA. Lupus can also cause life-threatening complications. These may include kidney failure, clotting problems, or seizures, which are not symptoms of RA.

RA, on the other hand, primarily attacks your joints. It affects the fingers, wrists, knees, and ankles. RA can also cause joints to deform, while lupus usually doesn’t.

RA can also be associated with inflammation in the lungs and around the heart in some cases, and with painful skin nodules. However, with the current therapies available, this is less common now than it has been in the past.

Pain associated with RA is usually worse in the morning and tends to get better as the day progresses. But the joint pain caused by lupus is constant throughout the day and can migrate.

Because these two diseases share some common characteristics, people can be misdiagnosed with RA when they actually have lupus, or vice versa, at the early stages of either disease.

Once RA is advanced, doctors can tell because the disease can cause bone erosion and deformity if appropriate therapy is not provided. Lupus, however, rarely causes bone erosions.

In the early stages of RA or lupus, doctors can usually make a diagnosis by looking at your symptoms. For example, lupus often affects the kidney, causes anemia, or leads to weight changes.

RA can also cause anemia, but may lead more frequently to pulmonary issues. A doctor might order a blood panel to check the health of your organs and to see if something else could be causing the symptoms.

Both lupus and rheumatoid arthritis can be difficult to diagnose. This is especially true early on in both diseases when there are few symptoms.

To be diagnosed with systemic lupus, you must meet at least four of the following diagnostic criteria:

  • acute cutaneous lupus, which includes malar rash, a rash (also known as the butterfly rash) that appears on the cheeks and nose
  • chronic cutaneous lupus, which includes discoid lupus, raised red patches on the skin
  • nonscarring alopecia, or hair thinning and breaking in multiple body sites
  • joint disease, which includes arthritis that doesn’t cause bone erosion
  • serositis symptoms, including inflammation of the lining of the heart or lungs
  • neurological symptoms, including seizure or psychosis
  • kidney symptoms, including protein or cellular casts in the urine, or a biopsy proving lupus kidney disease
  • hemolytic anemia
  • low white blood cell count
  • low platelet count
  • antibodies to double-stranded DNA
  • antibodies to Sm nuclear antigen
  • antiphospholipid antibodies, including antibodies to cardiolipin
  • presence of antinuclear antibodies, or ANA
  • low levels of complement, a type of immune protein
  • a positive test for antibodies against red blood cells

To be diagnosed with RA, you must get at least six points on the RA classifications scale. The scale is:

  • symptoms that affect at least one or more joints (up to five points)
  • testing positive for rheumatoid factor or anticitrullinated protein antibody in your blood (up to three points)
  • positive C-reactive protein (CRP) or erythrocyte sedimentation tests (one point)
  • symptoms lasting longer than six weeks (one point)

Comorbidity refers to having more than one disease at the same time. This is also known as overlap disease. People with lupus and people with RA can have symptoms of other conditions. It’s also possible for people to have symptoms of RA and lupus.

There’s no limit to how many chronic conditions you can have, and there is no time limit for when you can develop another chronic condition.

Diseases that often overlap with lupus include:

Diseases that often overlap with RA include:

  • Sjögren syndrome
  • autoimmune thyroid

There is no cure for lupus, but treatment can help you manage your symptoms. Many people with lupus take corticosteroids and other prescription drugs to treat joint inflammation and pain.

Others might need medication to treat skin rashes, heart disease, or kidney problems. Sometimes a combination of several drugs works best.

People with rheumatoid arthritis can get cortisone shots to control the inflammation. Sometimes, patients might need a knee or hip replacement later in life because the joint becomes too deformed. Many medications are available to control symptoms and prevent joint damage.

People with both lupus and RA will need to make a long-term plan with their doctors. This plan will include ways to help control the inflammation and pain. It will also help you minimize the complications of lupus and RA.

Long-term complications of lupus include heart and kidney damage. Lupus patients often suffer from abnormalities of the blood, including anemia and inflammation of the blood vessels. Without treatment, all of these can damage tissue.

Complications of untreated RA include permanent joint deformity, anemia, and lung damage. Treatment can prevent long term issues.