5 Diseases That Can Mimic Polymyalgia Rheumatica

Polymyalgia rheumatica (PMR) is an inflammatory disease, mostly seen in older adults, that causes pain and stiffness in certain areas of the body — often in the neck, shoulders, or hip area. These main symptoms, though, can also be caused by other health conditions, so it’s important for your doctor to rule out other diseases that may be mistaken for PMR when making a diagnosis.

A polymyalgia rheumatica diagnosis can involve a complicated process, in part because there is no definitive test for it. Instead, a PMR diagnosis is based on your symptoms and medical history, as well as a physical exam in which your doctor looks for telltale signs of the condition. Your doctor may also order blood tests to support a diagnosis of PMR or to point to a different health condition, according to Cleveland Clinic.

One feature that often distinguishes polymyalgia rheumatica from other diseases is that pain and stiffness in your shoulders or hip area is worse in the morning and gets better with physical activity. But there are other, potentially more definitive ways to confirm that you have PMR rather than another condition.

It’s very important to make sure you actually have polymyalgia rheumatica before you start treatment for the disease, since the standard treatment for PMR — which is typically highly effective — is a low dose of a corticosteroid such as prednisone (Deltasone), as noted by Mount Sinai.

Polymyositis is a rare degenerative condition that causes muscle inflammation and weakness. It tends to affect muscles all over your body, and eventually it can make movement difficult, according to Johns Hopkins Medicine.

While polymyalgia rheumatica tends to affect adults over age 50 — and often strikes between ages 70 and 80, according to the Mayo Clinic — polymyositis most often affects adults ages 31 to 60.

While experts don’t know what causes polymyositis, some believe that a virus or an autoimmune reaction (when your immune system attacks your own tissue) may be responsible for it.

While polymyalgia rheumatica tends to limit movement only in certain muscle groups, polymyositis can affect a much larger group of muscles — potentially making it difficult not only to run, walk, or lift objects, but also to swallow or breathe. Muscles closer to the center of your body are most likely to be affected, Johns Hopkins Medicine notes, which can include your heart muscle.

Symptoms of polymyositis may include:

Muscle pain and stiffness
Muscle weakness (often in your abdomen, shoulders, arms, or hip area)
Difficulty catching your breath
Difficulty swallowing
Irregular heart rhythm

To diagnose polymyositis, your doctor may order the following tests.

Blood tests: Certain blood tests can be used to identify muscle inflammation or autoimmune activity.

Electromyelogram (EMG): This test can identify abnormal electrical activity in muscles.

Magnetic resonance imaging (MRI): This imaging scan identifies muscle inflammation.

Muscle biopsy: In this procedure, your doctor takes a tiny sample of your muscle to look for abnormal changes under a microscope.

Fibromyalgia is a condition that causes pain and tenderness in different areas of your body, along with fatigue and difficulty sleeping, as noted by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS).

People with fibromyalgia have an increased sensitivity to pain, and tend to have ongoing and widespread pain in areas like the arms, legs, chest, abdomen, back, and buttocks. This pain may be described as aching, burning, or throbbing.

Unlike fibromyalgia, polymyalgia rheumatica tends to cause pain and stiffness only in limited areas of your body. PMR also doesn’t typically lead to tenderness or a general increase in pain sensitivity.

In addition to widespread pain, symptoms of fibromyalgia may include:

Fatigue
Difficulty sleeping
Muscle or joint stiffness
Tenderness or sensitivity to touch
Numbness or tingling (especially in arms or legs)
Difficulty concentrating or thinking
Increased sensitivity to light, sounds, smells, or hot or cold temperatures
Digestive problems like bloating or constipation

Fibromyalgia is diagnosed according to your symptoms, medical history, and a physical exam. There are no lab or imaging tests to identify fibromyalgia, but your doctor may order tests to rule out other diseases — such as rheumatoid arthritis or lupus, two of the conditions covered in this article.

Rheumatoid arthritis is a type of arthritis that most often affects your hands, knees, or ankles, causing joint pain and inflammation. It’s caused by your immune system attacking the lining of your joints (synovium), according to the Arthritis Foundation.

Unlike rheumatoid arthritis, polymyalgia rheumatica most often affects your neck, shoulders, or hip area — so your doctor may initially suspect one disease over the other based on the location of your symptoms. But while rheumatoid arthritis most often begins in your hands, wrists, knees, feet, or ankles, it can also affect other areas of your body — potentially leading your doctor to suspect polymyalgia rheumatica.

Rheumatoid arthritis typically begins in middle age — a bit before the typical age of onset for polymyalgia rheumatica. But certain symptoms of rheumatoid arthritis that develop at an older age may be mistaken for polymyalgia rheumatica.

While rheumatoid arthritis tends to make affected joints look red and swollen, this isn’t a main symptom of polymyalgia rheumatica. But both diseases tend to cause stiffness that’s worse in the morning and that affects both sides of your body.

On top of joint pain, stiffness, and swelling, additional symptoms of rheumatoid arthritis may include:

Fatigue
Low-grade fever
Eye symptoms like dryness, pain, or redness
Small lumps under your skin over bones (rheumatoid nodules)
Difficulty breathing due to lung damage

A diagnosis of rheumatoid arthritis is based on your symptoms and medical history, a physical exam, and tests that may include:

Blood tests: Your doctor may look for signs of inflammation and specifically for rheumatoid factor (RF), an antibody (protein) that is found in up to 80 percent of people with rheumatoid arthritis.

Imaging tests: Bone damage from rheumatoid arthritis may show up in X-ray, ultrasound, or magnetic resonance imaging (MRI) scans.

Lupus occurs when your body’s immune system attacks certain tissues and organs. It can be difficult to diagnose because its symptoms can resemble those of other diseases, according to Mayo Clinic.

One common telltale sign of lupus is a butterfly-shaped rash across your face, but this symptom doesn’t occur in all cases of the disease. Inflammation caused by lupus can affect your joints, skin, kidneys, brain, heart, and lungs.

Lupus is more common in women and tends to be diagnosed between ages 15 and 45, per Mayo Clinic — younger than the typical age of onset for polymyalgia rheumatica. More often than not, lupus is a mild disease that causes worse symptoms for a period of time — known as a flare — followed by improvement or even disappearance of your symptoms.

Symptoms of lupus can vary widely, and may include:

Fatigue
Fever
Joint pain and stiffness
Skin lesions (often after sun exposure)
Fingers or toes turning white or blue due to stress or exposure to cold temperatures
Chest pain or shortness of breath
Dry eyes
Headache
Confusion or memory problems

There isn’t a definitive test for lupus, but your doctor may order the following tests to help with a diagnosis.

Complete blood count (CBC): This blood test can identify anemia (inadequate red blood cells), which is often seen in lupus.

Erythrocyte sedimentation rate (ESR): This blood test can indicate systemic inflammation, which is often seen in lupus and many other diseases.

Antinuclear antibody (ANA) test: This blood test indicates heightened immune system activity, which is typically seen in lupus but also in other health conditions.

Kidney and liver function tests: These blood tests may show organ damage caused by lupus.

Urinalysis: Standard urine tests may show increased levels of protein or red blood cells, which may indicate reduced kidney function caused by lupus.

Lyme disease is a bacterial infection that people can get when they are bitten by an infected blacklegged (deer) tick, according to the Centers for Disease Control and Prevention (CDC).

While most cases of Lyme disease can be successfully treated by taking antibiotics for a few weeks, untreated Lyme disease can lead to serious symptoms and complications.

Ticks that carry Lyme disease are found throughout the eastern half of the United States and southern Canada, as well as in certain areas of the western United States and Canada, the CDC notes.

You’re more likely to get a tick bite during warmer months of the year, but it’s possible to get one during any season. Ticks live in wooded, grassy, and brush-covered areas and can be spread to people from your clothing or pets. Some people get Lyme disease from ticks in their own yard or neighborhood, according to the CDC.

The CDC lists signs and symptoms of Lyme disease that often appear within 3 to 30 days of a tick bite as:

Fever and chills
Headache
Fatigue
Muscle or joint pain
Swollen lymph nodes
Erythema migrans (EM) rash (often called a “bull's-eye” rash)

Untreated Lyme disease can also cause other potentially severe symptoms days to months after a tick bite, such as:

Severe headache
Neck stiffness
Drooping on one or both sides of your face
Severe joint pain and swelling
Muscle, tendon, or bone pain
Irregular heartbeat or heart palpitations
Dizziness
Shortness of breath
Pain, numbness, or tingling in your hands or feet

Lyme disease can be diagnosed through one or more blood tests using a single sample of blood. Your doctor may order these tests if your symptoms and history of possible tick exposure suggest that Lyme disease is possible, according to the CDC.

You may falsely test negative for Lyme disease if you were recently infected, and you may test positive for Lyme disease even after the infection has been treated successfully and you no longer have any symptoms.

An accurate diagnosis of polymyalgia rheumatica may require multiple tests to rule out other conditions, a process that can take some time. The diagnostic process can be even more complicated if you have two (or more) coexisting conditions. But sticking with it is important so that you get the right diagnosis and the right treatment.

If you do have polymyalgia rheumatica, there’s a good chance you’ll feel better quickly once you start taking a low dose of corticosteroids.

The Takeaway

Polymyalgia rheumatica primarily affects older adults. Symptoms include pain and stiffness in the neck, shoulders, or hips. But these symptoms also overlap with other health conditions, like fibromyalgia, rheumatoid arthritis, lupus, polymyositis, and Lyme disease. There’s no definitive testing to diagnose PMR, so it’s important for your doctor to rule out other health conditions to ensure proper treatment.

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The Takeaway