Both polymyalgia rheumatica (PMR) and rheumatoid arthritis (RA) are autoimmune conditions. They make your immune system attack your joints. These conditions have many similarities, but they have different causes.

PMR and RA are both inflammatory disorders that affect your joints.

PMR causes pain and stiffness in various joints, most commonly in your:

  • shoulders
  • neck
  • arms
  • hips

RA causes joint pain, inflammation, and stiffness. It usually affects your:

  • hands
  • wrists
  • knees
  • shoulders
  • elbows
  • ankles

Both PMR and RA are autoimmune conditions. This means they cause your immune system to attack your joints. These two conditions have many similarities, such as shoulder involvement. However, they have different causes and methods of treatment.

Keep reading to learn about the similarities and differences between PMR and RA, including their symptoms, causes, risk factors, diagnosis, and treatment.

PMR and RA share several symptoms:

Additionally, both conditions are more common in women than in men.

However, there are also some key differences between the two conditions:

  • Other than the shoulders, RA and PMR affect different types of joints:
    • RA is most common in the small joints of the hands and feet.
    • PMR never involves feet but can affect your neck and hips.
  • Joint swelling is very common in RA but rarely happens in PMR.
  • RA typically begins between the ages of 30 and 50, while PMR usually occurs after age 50.
  • PMR has a rapid symptom onset, while RA symptoms appear more gradually.

Both conditions occur as a result of malfunctioning of your autoimmune system. However, they have different causes.

Causes of PMR

The exact cause of PMR is not known. Many researchers believe it’s a combination of genetic and environmental factors, including aging.

Causes of RA

Like PMR, RA has both a genetic and an environmental component. However, the genes that trigger RA are different from those responsible for PMR.

Aside from your genes, several other risk factors can trigger RA or PMR.

Risk factors for PMR

Not much is known about the risk factors of PMR. It sometimes occurs after viral infections and vaccinations. In very rare cases, it can be a complication of immunotherapy used in cancer treatment.

Risk factors for RA

RA has several risk factors:

  • smoking
  • obesity
  • exposure to certain chemical compounds
  • the presence of hormones such as estrogen
  • viral or bacterial infections
  • stress or mental trauma

It’s unlikely for one condition to cause the other. However, some people may receive diagnoses of both conditions in their lifetime. This is usually due to an initial misdiagnosis.

It’s also unlikely for you to have both PMR and RA at the same time.

One condition that does often co-occur with PMR is called giant cell arteritis or temporal arteritis. It is a type of blood vessel inflammation.

Correct diagnosis of PMR or RA is extremely important because, although they share many features, the two conditions have different treatment methods.

To make an accurate diagnosis, a rheumatologist will perform a physical exam, ask about your medical history, and run several tests to check for inflammation and certain indicators in your blood.

Healthcare professionals commonly order the following labs when diagnosing either PMR or RA:

No single test can definitively diagnose either PMR or RA. Some people may receive a final diagnosis only after a doctor assesses their response to initial treatment.

Doctors don’t yet know of a cure for either PMR or RA, but appropriate treatment may help manage your symptoms and delay disease progression.

The main treatment of PMR is corticosteroids, such as prednisolone, taken orally (by mouth). You may need to take this medication for years or even for your whole life.

On the other hand, when treating RA, doctors may use corticosteroids for only a short period when starting treatment. Disease-modifying antirheumatic drugs (DMARDs), biologics, and JAK inhibitors are more effective for this condition.

In addition to medications, a healthy lifestyle — including an anti-inflammatory diet, regular exercise, and rest — is helpful for both PMR and RA.

Be sure to consult a doctor if you have any joint-related symptoms, such as:

  • pain
  • inflammation
  • swelling
  • limited range of motion

In addition, contact your rheumatologist if you have a diagnosis of either PMR or RA and your treatment doesn’t seem to help.

PMR and RA are both autoimmune conditions that affect your joints. They have many similarities, which can complicate and delay diagnosis. No single test can diagnose either condition, but a trained rheumatologist can spot the unique features of each condition.

While PMR is usually treated with oral prednisolone, doctors use DMARDs, biologics, and JAK inhibitors to treat RA.