Polymyalgia rheumatica (PMR) causes symptoms similar to those of several other conditions, such as rheumatoid arthritis, lupus, and fibromyalgia. For this reason, doctors can misdiagnose it.

PMR causes widespread muscle stiffness, aching, and pain that is often worse in the morning or after extended periods of inactivity. It affects both sides of the body equally and is common in those over 50 years of age.

Other symptoms of PMR include:

This article looks at the diseases that mimic PMR, including their similarities and differences. It also explains how doctors tell these conditions apart and make a diagnosis.

A man sat on a bed facing a window, holding his back due to polymyalgia rheumatica pain.Share on Pinterest
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According to the American College of Rheumatology, PMR is a condition that causes widespread aching and stiffness in joints around the body. It often affects the:

  • upper arms and shoulders
  • neck
  • hips
  • lower back
  • thighs

The average age of onset is 70 years old. PMR can affect anyone, but it occurs slightly more often in females than males and is more common in white people. The reasons for this are unclear. Doctors do not know what causes PMR, but it appears to be driven by inflammation.

PMR typically lasts between 1–5 years before resolving, but this can vary. During that time, people can manage the symptoms using medications, exercise, and rest.

Approximately 15% of people with PMR also develop a potentially serious condition known as giant cell arteritis, which causes narrowing or blockages in large blood vessels around the head, neck, and arms. The symptoms of giant cell arteritis include:

  • headaches
  • visual difficulties, such as double vision or vision loss
  • jaw pain while eating
  • scalp tenderness or aching around the temples

Polymyalgia rheumatica shares many symptoms with a range of other diseases, including:

RA is an autoimmune disease that occurs when the immune system attacks the joints. It causes pain and stiffness in the joints, similar to PMR. People with RA can also experience fatigue, a high temperature, low appetite, and weight loss. Due to these similarities, RA and PMR are easy to mix up.

Additionally, both RA and PMR tend to affect both sides of the body and occur more frequently in older adults. Around 30% of people with PMR have joint swelling and degeneration, which are also symptoms of RA.

However, there are some differences between the symptoms of PMR and RA. Not everyone with PMR will develop joint swelling, whereas in RA, this is a key symptom. Additionally, RA often begins in the hands, feet, wrists, and ankles. PMR does not usually affect these joints.

Lupus is another autoimmune condition. However, instead of the immune system specifically attacking the joints, it attacks various tissues and organs. The main symptoms are joint and muscle pain, a rash over the nose and cheeks, and extreme fatigue. Aside from the butterfly-shaped rash on the face, lupus can seem very similar to PMR.

Other symptoms of lupus may include:

  • mouth sores
  • headaches
  • a high temperature
  • hair loss
  • loss of appetite and weight loss
  • skin that is sensitive to the sun

Fibromyalgia is a condition that causes chronic pain across the body. Similar to PMR, it causes muscle stiffness and tension, especially in the morning. It can also cause fatigue.

Other symptoms of fibromyalgia include:

  • increased sensitivity to pain
  • difficulty sleeping
  • difficulty thinking or remembering
  • headaches
  • digestive symptoms similar to irritable bowel syndrome

A key difference between fibromyalgia and PMR is that fibromyalgia is not inflammatory, so it will not respond to medications that reduce pain by lowering inflammation.

Lyme disease is a bacterial infection that spreads through tick bites. It causes joint pain and stiffness, fever, and fatigue, much like PMR. It can also cause:

  • a rash around the bite, which may resemble a bull’s-eye
  • chills
  • swollen lymph nodes

If Lyme disease is left untreated, it can cause more advanced symptoms, such as:

  • severe headaches
  • neck stiffness
  • loss of muscle tone in the face, or facial drooping
  • rashes on other areas of the body
  • severe arthritis, particularly of the knees or larger joints
  • dizziness
  • shortness of breath
  • heart palpitations
  • nerve pain or numbness
  • shooting or tingling sensations in the hands and feet

As ticks are tiny, their bites are easy to miss. Additionally, while there are tests for Lyme disease, they are not always accurate.

If Lyme disease is a possibility, a doctor may prescribe antibiotics to treat the infection. If they do not work, it may indicate that Lyme disease is not the cause of the symptoms.

People with cancer experience some of the symptoms associated with PMR, including fatigue, fever, loss of appetite, and weight loss.

There is also an association between a PMR diagnosis and an increased risk of cancer. A 2020 study found a higher prevalence of cancer in people with PMR during a 40-week follow-up.

There is no single test for PMR, which can make diagnosis a challenge. Instead, doctors will begin by:

  • asking people about their symptoms
  • taking a medical history
  • conducting a physical examination of the affected joints

The next stage of diagnosis may involve blood tests to rule out other conditions, such as lupus and RA. These tests may include:

  • a complete blood count
  • C-reactive protein (CRP)
  • erythrocyte sedimentation rate (ESR)
  • rheumatoid factor (RF)
  • anti-cyclic citrullinated peptide (anti-CCP)
  • antinuclear antibody (ANA)

CRP and ESR tests check for inflammation in the body, which can be a sign of PMR. If both the ESR and CRP are normal, a doctor is unlikely to diagnose PMR. However, some people with PMR have normal or only slightly raised levels of both.

A doctor may also use ultrasound or MRI scan to check for bursitis, which is inflammation around the joints.

If a person could have giant cell arteritis, the doctor will also examine arteries to see if they are inflamed or tender or have a reduced pulse. They may take a small tissue sample to confirm the diagnosis, but this is not always necessary.

Learn about the treatments for PMR.

Some questions people might want to ask a doctor about the process of diagnosing PMR include:

  • Could these symptoms be due to another condition?
  • What tests will you perform to find out the cause?
  • Do I need to do anything to prepare for the tests?
  • How reliable are the test results?
  • If I have PMR, what are the best treatments?
  • Are there lifestyle changes I need to make to relieve the symptoms?

PMR causes widespread pain and stiffness around the joints, particularly larger joints, such as the shoulders. It also causes fever, fatigue, appetite loss, and weight loss. These symptoms can be similar to those of other diseases, including RA, lupus, Lyme disease, and fibromyalgia.

A person with symptoms of PMR, or diseases that can mimic PMR, should speak with a doctor. This is especially important if they may have had a recent tick bite or show signs of giant cell arteritis. Early treatment can make PMR, as well as other similar conditions, easier to manage.