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Polymyositis

Table of Contents

Polymyositis

PM

Polymyositis is a type of inflammatory myopathy, which refers to a group of muscle diseases characterized by chronic muscle inflammation and weakness. The disease is more common among women and among black individuals. Learn about causes, symptoms and treatment options.

The three major types of muscle tissue are cardiac, skeletal, and smooth

Image by TheVisualMD

Summary

Polymyositis

Image by Jensflorian

Polymyositis

Polymyositis: Inflammatory infiltrates in a muscle biopsy. Holes in the muscle cell vacuoles, deposits of abnormal proteins within the cells and in filamentous inclusions (hence the name inclusion body myositis} are clearly visible in the cellular interstitial space.

Image by Jensflorian

What Is Polymyositis?

Polymyositis is one of a group of rare diseases called the inflammatory myopathies that involve chronic (long-standing) muscle inflammation and weakness, and in some cases, pain. Myopathy is a general term used to describe a number of conditions affecting the muscles. All myopathies can cause muscle weakness. Both children and adults can be affected.

Polymyositis affects skeletal muscles (the type involved in body movement) on both sides of the body. It is rarely seen in people younger than age 20. Generally, the onset occurs between age 30 and 60. Untreated progressive muscle weakness may lead to difficulty doing the following actions:

Swallowing
Speaking
Rising from a sitting position
Climbing stairs
Lifting objects
Reaching overhead

Some people with polymyositis also may develop:

Arthritis
Shortness of breath
Heart arrhythmias (irregular heartbeats)
Congestive heart failure (when the heart is no longer able to pump out enough oxygen-rich blood)

In some cases of polymyositis, the distal muscles, which are the muscles away from the center of the body, such as those in the forearms and around the ankles and wrists, may be affected as the disease progresses. The disorder also may be associated with collagen-vascular or autoimmune diseases such as lupus, in which the body's immune response system that normally defends against infection and disease attacks its own muscle fibers, blood vessels, connective tissue, organs, or joints.

Source: National Institute of Neurological Disorders and Stroke (NINDS)

Additional Materials (3)

Polymyositis Overview : Johns Hopkins Myositis Center

Video by Johns Hopkins Rheumatology/YouTube

Polymyositis and Inclusion Body Myositis (IBM)

Video by Learning in 10/YouTube

3 Scientific Reasons Why Your Back Hurts

Video by Seeker/YouTube

3:56

Polymyositis Overview : Johns Hopkins Myositis Center

Johns Hopkins Rheumatology/YouTube

7:59

Polymyositis and Inclusion Body Myositis (IBM)

Learning in 10/YouTube

5:13

3 Scientific Reasons Why Your Back Hurts

Seeker/YouTube

Causes

Idiopathic - Unknown

Image by PaliGraficas/Pixabay

Idiopathic - Unknown

Image by PaliGraficas/Pixabay

What Causes Polymyositis?

For some people, symptoms of polymyositis may be associated with connective tissue disorders, viral infections such as HIV-AIDS, other autoimmune diseases, or diseases that affect the ability to breathe. This means that individuals who have any of these diseases are at a higher risk to develop polymyositis.

Source: Genetic and Rare Diseases (GARD) Information Center

Inheritance

Mutation

Image by National Human Genome Research Institute (NHGRI)

Mutation

A mutation is a change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection. Germline mutations (that occur in eggs and sperm) can be passed on to offspring, while somatic mutations (that occur in body cells) are not passed on.

Image by National Human Genome Research Institute (NHGRI)

How Is Polymyositis Inherited?

Changes (mutations) in a specific gene are not known to cause polymyositis. In general, autoimmune diseases are thought to be caused by a combination of genetic and environmental factors. In some cases, multiple people in the same family may be affected by an autoimmune disease. Therefore, it is possible for people with polymyositis to have other family members affected by the disease or by other autoimmune diseases.

Source: Genetic and Rare Diseases (GARD) Information Center

Symptoms

Muscle atrophy

Image by CNX Openstax

Muscle atrophy

Muscle mass is reduced as muscles atrophy with disuse.

Image by CNX Openstax

What Are the Signs and Symptoms of Polymyositis?

Other symptoms of polymyositis include arthritis, shortness of breath, difficulty swallowing and speaking, mild joint or muscle tenderness, fatigue, and heart arrhythmias. People with polymyositis may have an increased risk to develop cancer.

Source: Genetic and Rare Diseases (GARD) Information Center

Additional Materials (1)

Polymyositis Signs & Symptoms : Johns Hopkins Myositis Center

Video by Johns Hopkins Rheumatology/YouTube

2:55

Polymyositis Signs & Symptoms : Johns Hopkins Myositis Center

Johns Hopkins Rheumatology/YouTube

Diagnosis

Electromyography

Image by BruceBlaus

Electromyography

An illustration of an electromyogram procedure.

Image by BruceBlaus

How Is Polymyositis Diagnosed?

Blood tests to measure the levels of certain muscle enzymes, such as creatine kinase and aldolase
Blood tests to detect specific autoantibodies that cause the autoimmune response associated with polymyositis
Electromyography to check the health of the muscles and the nerves that control them
Imaging studies such as MRI scan or muscle ultrasound to detect muscle inflammation
A muscle biopsy to diagnose muscle abnormalities such as inflammation, damage, or infection

Source: Genetic and Rare Diseases (GARD) Information Center

Additional Materials (2)

Needle EMG of paravertebral muscles(2J009)

The needle EMG of paravertebral muscles

Image by Kychot/Wikimedia

Polymyositis Diagnosis : Johns Hopkins Myositis Center

Video by Johns Hopkins Rheumatology/YouTube

Needle EMG of paravertebral muscles(2J009)

Kychot/Wikimedia

2:09

Polymyositis Diagnosis : Johns Hopkins Myositis Center

Johns Hopkins Rheumatology/YouTube

Creatine Kinase (CK) Blood Test

Creatine Kinase (CK) Blood Test

Also called: Creatine Kinase, Total CK, Creatine Phosphokinase, CPK

This test measures the amount of creatine kinase (CK) in a sample of your blood. CK is an enzyme that helps in producing energy from muscles. High CK levels may be a sign of damage or disease in your muscles, heart, or brain.

Creatine Kinase (CK) Blood Test

Also called: Creatine Kinase, Total CK, Creatine Phosphokinase, CPK

This test measures the amount of creatine kinase (CK) in a sample of your blood. CK is an enzyme that helps in producing energy from muscles. High CK levels may be a sign of damage or disease in your muscles, heart, or brain.

{"label":"Creatine kinase reference range","scale":"lin","step":0.1,"hideunits":false,"items":[{"flag":"abnormal","label":{"short":"Low","long":"Low","orientation":"horizontal"},"values":{"min":0,"max":24},"text":"Low CK levels often result from an individual having low muscle mass or body weight. People who have been confined to bed rest for extended periods of time will display abnormally low CK levels. A low CK level could be the result of alcoholic liver disease or a connective tissue disease.","conditions":["Alcoholic liver disease","Cachexia","Connective tissue disease","Kidney disease","Extreme weight loss","Lupus","Malnutrition","Myasthenia gravis","Muscular dystrophy","Rheumatoid arthritis","Sj\u00f6gren syndrome"]},{"flag":"normal","label":{"short":"Normal","long":"Normal","orientation":"horizontal"},"values":{"min":24,"max":204},"text":"CK levels are a reflection of total muscle mass. The normal range for total CK varies by age and gender. Race is also known to affect CK levels. Black people have naturally higher levels of CK. Some people with a muscular build also have higher levels of CK. Women generally have lower CK levels than men, because they typically have less muscle mass. Additionally, a pregnant woman will display lower CK levels than a non-pregnant woman.","conditions":[]},{"flag":"abnormal","label":{"short":"High","long":"High","orientation":"horizontal"},"values":{"min":204,"max":500},"text":"A high CK result generally means you have some type of muscle damage. High CK is found after trauma, surgery, and exercise. You may have more than one CK test to see if your levels go up or down. CK levels that stay high or increase may mean that muscle damage is continuing to happen. Further testing may be necessary to determine the type of muscles affected.","conditions":["Brain injury","Stroke","Heart attack","Seizures","Muscle disorder","Myopathy","Dermatomyositis","Polymyositis","Rhabdomyolysis","Electric shock","Myocarditis","Pulmonary infarction","Malignant hyperthermia","Hypothyroidism","Hyperthyroidism"]}],"units":[{"printSymbol":"U\/L","code":"U\/L","name":"enzyme unit per liter"}],"value":114,"disclaimer":"Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are \"within normal limits.\""}[{"abnormal":0},{"normal":0},{"abnormal":0}]
Use the slider below to see how your results affect your health.
U/L
24
204
Your result is Normal.
CK levels are a reflection of total muscle mass. The normal range for total CK varies by age and gender. Race is also known to affect CK levels. Black people have naturally higher levels of CK. Some people with a muscular build also have higher levels of CK. Women generally have lower CK levels than men, because they typically have less muscle mass. Additionally, a pregnant woman will display lower CK levels than a non-pregnant woman.
Related conditions
A CK test is most often used to help diagnose and monitor:
- Muscle injuries, including injuries from accidents, serious burns, or extreme exercise.
- Muscle diseases, including:
  Muscular dystrophy, a group of inherited muscle diseases that weaken muscles over time.
  Rhabdomyolysis, or "rhabdo," a rapid breakdown of muscle tissue which releases proteins and electrolytes into the blood. This uncommon condition can damage the heart and lead to sudden kidney failure. Rhabdo has many causes, including serious injuries, working in very hot places, overusing muscles, and certain medicines and medical conditions that affect the muscles.
  Myositis, a group of rare diseases that involve long-term muscle inflammation (swelling), weakness, and sometimes pain.
In certain cases, a CK test may be used to help diagnose a heart attack. Another blood test, called a troponin test is used more often. That's because troponin testing is better at finding damage to the heart muscle from a heart attack.
If you've had a stroke, a CK test may be done to find out how severe it was. The test may also help predict the chance that you may have another stroke.
You may need a CK test if you have symptoms of a muscular disorder. These include:
- Muscle pain and/or cramps
- Muscle weakness
- Balance problems and/or falling a lot
- Numbness or tingling
- Dark colored urine (pee)
- Swollen legs or feet
You may also need this test if you:
- Have had an injury that crushed or tore your muscles
- Have had serious burns
- Take certain medicines that may cause muscle damage, such as statins to lower blood cholesterol
- Have had a stroke or traumatic brain injury (TBI)
Normal CK levels for you will depend on:
- Your age, sex, and race
- How much muscle you have
- How physically active you are
If your CK level is higher than normal, it usually means you have some type of muscle damage. CK levels may not reach their highest until up to two days after certain injuries. So, you may have more than one CK test to see if your levels go up or down. CK levels that stay high or increase may mean that muscle damage is continuing to happen.
But a CK test result can't show where the damage is or what's causing it. Your provider will consider your symptoms and medical history to understand what your test results mean.
If the source of high or increasing CK levels isn't clear, you may need a more specific type of CK test to find out if the CK is coming from your muscles, heart, or brain. This more specific test is called a CK isoenzymes test.
To diagnose the condition causing high CK levels, you may need other types of tests, too. The tests you have will depend on which types of CK enzymes are high as well as your symptoms and medical history.
If you have questions about any of your test results or diagnosis, talk with your provider.
1. Creatine Kinase: MedlinePlus Medical Test [accessed on Jan 27, 2024]
2. Creatine phosphokinase test: MedlinePlus Medical Encyclopedia [accessed on Jan 27, 2024]
3. Creatine Kinase (Blood) - Health Encyclopedia - University of Rochester Medical Center [accessed on Jan 27, 2024]
4. HealthMatters.io LLC. Creatine kinase - Lab Results explained | HealthMatters.io [accessed on Jan 27, 2024]
5. Creatine kinase (CK) Test - Bay Biosciences, LLC.. Oct 19, 2022 [accessed on Jan 27, 2024]

Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

Additional Materials (16)

This browser does not support the video element.

Blockage Leads to Heart Attack

Risk factors increase the likelihood that you'll develop cardiovascular disease, and the more risk factors you have, the greater your chances of developing it. Fortunately, most of these risk factors are within your control, like high cholesterol and high blood pressure levels, being overweight, smoking, lack of exercise, overconsumption of alcohol, unmanaged diabetes, and stress. Factors you can't control include genetics and aging.

Video by TheVisualMD

This browser does not support the video element.

Women's Cardiovascular Health

Watch Dr. Mehmet Oz and other renowned cardiologists as they talk about this major killer, known in the medical world as a "myocardial infarction." Step inside the human body in a way that lets you completely understand what a heart attack is all bout, how and why they happen, what to do in the event of a heart attack, and how you can take steps to avoiding one.

Video by TheVisualMD

Heart attack (myocardial infarction) warning signs in women.

Image by U.S. Department of Health and Human Services Office on Women's Health

Myocardial Infarction (Heart Attack)

An illustration depicting a heart attack and chest pain.

Image by BruceBlaus

Myocardial infarction

Inferior wall infarction, short axis echocardiography view

Image by Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist

Myocardial infarction - Post-infarction ventricular septal defect

Post-infarction ventricular septal defect, short axis echocardiography view

Image by Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist

Myocardial infarction - Post-infarction ventricular septal defect

Post-infarction echocardiographic views of ventricular septal defect

Image by Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist

Heart Attack Symptoms

Symptoms of a heart attack are often more severe and longer-lasting than those of angina. Heart attacks can occur at any time or place, when you're resting or when you're in motion. Heart attacks can strike without warning, but there may be signs and symptoms, like angina, in advance.

Image by TheVisualMD

Heart Attack Symptoms

Symptoms of a heart attack are often more severe and longer-lasting than those of angina. Heart attacks can occur at any time or place, when you're resting or when you're in motion. Heart attacks can strike without warning, but there may be signs and symptoms, like angina, in advance.

Image by TheVisualMD

What Is a Heart Attack?

Sometimes the surface of a plaque in a coronary artery ruptures. The rupture releases substances that make platelets stickier, encouraging clots to form on the surface of the plaque. The clot can block the flow of blood through the already-narrowed artery entirely. Without blood, heart muscle tissue starts to die in what's termed a myocardial infarction- a heart attack.

Image by TheVisualMD

Lipoprotein (a) or Lp(a), Heart Attack

LDL, HDL and total cholesterol have become standard biomarkers for heart disease. And yet half of all people who suffer heart attacks have normal cholesterol levels. For that reason, researchers have looked for other biomarkers that might help identify people at risk for cardiovascular disease. Lp(a) is a lipoprotein that closely resembles LDL, and like LDL, elevated levels of Lp(a) are associated with a higher risk of heart disease. Unlike LDL, however, Lp(a) levels are believed to be largely genetic.

Image by TheVisualMD

Cholesterol, Low-Density Lipoprotein (LDL), Heart Disease, Heart Attack

There are two main types of cholesterol particles found in the bloodstream: HDL (high-density lipoprotein, or \"good\" cholesterol); and LDL (low-density lipoprotein, or \"bad\" cholesterol). LDL often leads to the formation of plaque deposits that can clog arteries and increase the risk of heart disease. Each year 1.2 million people have a heart attack (for nearly half of them, it's not their first). More than 600,000 individuals die from heart disease each year, making it the leading cause of death for both men and women.

Image by TheVisualMD

Heart Attack Caused by Ischemia

Thromboembolisms can cause heart attacks. A clot may lodge in one of the heart's coronary arteries (the arteries that supply the heart muscle tissue with blood) and block blood flow. The tissue becomes starved of oxygen (a condition called ischemia) and is damaged or dies.

Image by TheVisualMD

Lipoprotein (a) or Lp(a), Cardiovascular Disease

In order for fats to travel freely in the bloodstream, they must be packaged as lipoproteins. The two main types are HDL (high-density lipoprotein, or \"good\" cholesterol) and LDL (low-density lipoprotein, or \"bad\" cholesterol). There are other lipoproteins, however. Lipoprotein (a), or Lp(a), is one that resembles LDL and, like LDL, elevated levels of Lp(a) are associated with a higher risk of cardiovascular disease. Unlike LDL, however, Lp(a) levels are believed to be largely genetic.

Image by TheVisualMD

Heart attack (myocardial infarct) diagnosis | NCLEX-RN | Khan Academy

Video by khanacademymedicine/YouTube

What causes a heart attack?

Video by multiedmedical/YouTube

0:23

Blockage Leads to Heart Attack

TheVisualMD

2:56

Women's Cardiovascular Health

TheVisualMD

Heart attack (myocardial infarction) warning signs in women.

U.S. Department of Health and Human Services Office on Women's Health

Myocardial Infarction (Heart Attack)

BruceBlaus

Myocardial infarction

Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist

Myocardial infarction - Post-infarction ventricular septal defect

Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist

Myocardial infarction - Post-infarction ventricular septal defect

Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist

Heart Attack Symptoms

TheVisualMD

Heart Attack Symptoms

TheVisualMD

What Is a Heart Attack?

TheVisualMD

Lipoprotein (a) or Lp(a), Heart Attack

TheVisualMD

Cholesterol, Low-Density Lipoprotein (LDL), Heart Disease, Heart Attack

TheVisualMD

Heart Attack Caused by Ischemia

TheVisualMD

Lipoprotein (a) or Lp(a), Cardiovascular Disease

TheVisualMD

10:45

Heart attack (myocardial infarct) diagnosis | NCLEX-RN | Khan Academy

khanacademymedicine/YouTube

2:54

What causes a heart attack?

multiedmedical/YouTube

Aldolase Test

Aldolase Test

Also called: ALS

Aldolase is a protein that can be mostly found in muscle tissue. An aldolase test is sometimes ordered along with other tests to help diagnose and monitor muscle and liver damage.

Aldolase Test

Also called: ALS

Aldolase is a protein that can be mostly found in muscle tissue. An aldolase test is sometimes ordered along with other tests to help diagnose and monitor muscle and liver damage.

{"label":"Aldolase Reference Range","scale":"lin","step":0.1,"hideunits":false,"units":[{"printSymbol":"U\/L","code":"U\/L","name":"enzyme unit per liter"}],"items":[{"flag":"abnormal","label":{"short":"Low","long":"Low","orientation":"horizontal"},"values":{"min":0,"max":1},"text":"Decreased levels of aldolase can be related to a low muscle mass.","conditions":["Fructose intolerance","Muscle-wasting disease","Late-stage muscular dystrophy"]},{"flag":"normal","label":{"short":"Normal","long":"Normal","orientation":"horizontal"},"values":{"min":1,"max":7.5},"text":"Normal results may slightly vary based on the laboratory and the method used.","conditions":[]},{"flag":"abnormal","label":{"short":"High","long":"High","orientation":"horizontal"},"values":{"min":7.5,"max":20},"text":"Increased aldolase levels usually indicate muscle or liver damage. ","conditions":["Muscle damage","Muscle diseases","Muscular dystrophy","Dermatomyositis","Heart attack","Liver diseases","Hepatitis","Mononucleosis","Prostate cancer","Pancreatic cancer","Liver cancer","Gangrene"]}],"value":4.3}[{"abnormal":0},{"normal":0},{"abnormal":0}]
Use the slider below to see how your results affect your health.
U/L
1
7.5
Your result is Normal.
Normal results may slightly vary based on the laboratory and the method used.
Related conditions
Normal aldolase values can range from 1.0 to 7.5 units per liter (0.02 to 0.13 microkat/L). However, normal reference ranges may vary slightly among different laboratories.
Low aldolase levels can be related to a low muscular mass.
High aldolase levels may be due to:
- Muscle damage
- Muscle diseases, such as muscular dystrophy or dermatomyositis, among others.
- Heart attack
- Liver diseases
- Hepatitis (liver inflammation)
- Mononucleosis (which is an infection caused by a virus)
- Prostate, pancreatic, or liver cancer
- Gangrene (tissue death)
1. Aldolase blood test: MedlinePlus Medical Encyclopedia [accessed on Sep 29, 2018]
2. ALS - Clinical: Aldolase, Serum [accessed on Sep 29, 2018]
3. Aldolase [accessed on Sep 29, 2018]
4. 002030: Aldolase | LabCorp [accessed on Sep 29, 2018]
5. Aldolase Test: Purpose, Procedure, and Results [accessed on Sep 29, 2018]

Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

Additional Materials (2)

3D visualization reconstructed from scanned human data of an oblique lateral view of digestive organs

3D visualization reconstructed from scanned human data of an oblique lateral view of digestive organs. The sphincters of the stomach are highlighted. The digestive system is comprised of an alimentary canal and accessory organs; together they break down complex food stuffs into the simple structures the body can use, absorb the nutrients into the blood stream, and eliminate the leftover waste. Food passes from the esophagus to the stomach through the cardiac sphincter, which prevents chyme from returning back to the esophagus. After chemical and mechanical digestion in the stomach, the chyme moves on to the first part of the small intestine (the duodenum) through the pyloric sphincter, which controls the rate of stomach emptying.

Image by TheVisualMD

Male Abdomen with Visible Digestive Organ

3D visualiztion reconstructed from scanned human data of an oblique lateral view of digestive organs. The sphincters of the stomach are highlighted. The digestive system is comprised of an alimentary canal and accessory organs; together they break down complex food stuffs into the simple structures the body can use, absorb the nutrients into the blood stream, and eliminate the leftover waste. Food passes from the esophagus to the stomach through the cardiac sphincter, which prevents chyme from returning back to the esophagus. After chemical and mechanical digestion in the stomach, the chyme moves on to the first part of the small intestine (the duodenum) through the pyloric sphincter, which controls the rate of stomach emptying.

Image by TheVisualMD

3D visualization reconstructed from scanned human data of an oblique lateral view of digestive organs

TheVisualMD

Male Abdomen with Visible Digestive Organ

TheVisualMD

Electromyography (EMG) and Nerve Conduction Studies

Electromyography (EMG) and Nerve Conduction Studies

Also called: Electrodiagnostic study, Electrodiagnosis, EDX

Electromyography (EMG) and nerve conduction studies are tests that measure the electrical activity of muscles and nerves. They are used to find out if you have a disorder of your muscles, nerves, or both.

Electromyography (EMG) and Nerve Conduction Studies

Also called: Electrodiagnostic study, Electrodiagnosis, EDX

Electromyography (EMG) and nerve conduction studies are tests that measure the electrical activity of muscles and nerves. They are used to find out if you have a disorder of your muscles, nerves, or both.

Electromyography (EMG) and nerve conduction studies are tests that measure the electrical activity of muscles and nerves. Nerves send out electrical signals to make your muscles react in certain ways. As your muscles react, they give off these signals, which can then be measured.
- An EMG test looks at the electrical signals your muscles make when they are at rest and when they are being used.
- A nerve conduction study measures how fast and how well the body's electrical signals travel down your nerves.
EMG tests and nerve conduction studies can both help find out if you have a disorder of your muscles, nerves, or both. These tests can be done separately, but they are usually done at the same time.
You may need these tests if you have symptoms of a muscle or nerve disorder. These symptoms include:
- Muscle weakness
- Tingling or numbness in arms, legs, hands, feet, and/or face
- Muscle cramps, spasms, and/or twitching
- Paralysis of any muscles
For an EMG test:
- You will sit or lie down on a table or bed.
- Your provider will clean the skin over the muscle being tested.
- Your provider will place a needle electrode into the muscle. You may have slight pain or discomfort when the electrode is inserted.
- The machine will record the muscle activity while your muscle is at rest.
- Then you will be asked to tighten (contract) the muscle slowly and steadily.
- The electrode may be moved to record activity in different muscles.
- The electrical activity is recorded and shown on a video screen. The activity is displayed as wavy and spiky lines. The activity may also be recorded and sent to an audio speaker. You may hear popping sounds when you contract your muscle.
For a nerve conduction study:
- You will sit or lie down on a table or bed.
- Your provider will attach one or more electrodes to a certain nerve or nerves using tape or a paste. The electrodes, called stimulating electrodes, deliver a mild electrical pulse.
- Your provider will attach different types of electrodes to the muscle or muscles controlled by those nerves. These electrodes will record the responses to the electrical stimulation from the nerve.
- Your provider will send a small pulse of electricity through the stimulating electrodes to stimulate the nerve to send a signal to the muscle.
- This may cause a mild tingling feeling.
- Your provider will record the time it takes for your muscle to respond to the nerve signal.
- The speed of the response is called the conduction velocity.
If you are having both tests, the nerve conduction study will be done first.
If your results were not normal, it can indicate a variety of different conditions. Depending on which muscles or nerves are affected, it may mean one of the following:
- Carpal tunnel syndrome, a condition that affects nerves in the hand and arm. It's usually not serious, but can be painful.
- Herniated disc, a condition that happens when a part of your spine, called a disc, is damaged. This puts pressure on the spine, causing pain and numbness
- Guillain-Barré syndrome, an autoimmune disorder that affects the nerves. It can lead to numbness, tingling, and paralysis. Most people recover from the disorder after treatment
- Myasthenia gravis, a rare disorder that causes muscle fatigue and weakness.
- Muscular dystrophy, an inherited disease that seriously affects muscle structure and function.
- Charcot-Marie-Tooth disease, an inherited disorder that causes nerve damage, mostly in the arms and legs.
- Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. This is a progressive, ultimately fatal, disorder that attacks nerve cells in your brain and spinal cord. It affects all the muscles you use to move, speak, eat, and breathe.
If you have questions about your results, talk to your health care provider.

Additional Materials (7)

Schematic diagram of normal sinus rhythm for a human heart as seen on ECG.

Schematic representation of normal ECG trace (sinus rhythm) with waves, segments, and intervals labeled. The QT interval is marked by blue stripe at bottom.

Image by Created by Agateller (Anthony Atkielski), converted to svg by atom.

Limb leads

Limb leads, standard placement of the limb leads for electrocardiography.

Image by !Original: MoodyGrooveVector: Twisp This SVG diagram includes elements that have been taken or adapted from this diagram: Wikicouple.svg. /Wikimedia

Precordial leads in ECG

Placement of the precordial leads in electrocardiography.

Image by Mikael Häggström/Wikimedia

Limb leads of EKG

Derivation of the limb leads

Image by Npatchett/Wikimedia

Spatial orientation of EKG leads

Spatial orientation of EKG leads

Image by Npatchett

Animation of ECG Limb Leads and Electrical Conduction Through the Heart

This is a 30-frame animation of how the electrical conduction through the heart creates a normal ECG for all 3 limb leads.

Image by 10ebyu10e/Wikimedia

Willem Einthoven ECG

In contrast to what the name of this file may suggest, this picture does not represent the ECG machine built by Willem Einthoven and his team. It shows an early commercial ECG machine, built in 1911 by the Cambridge Scientific Instrument Company (Christoph Zywietz, A Brief History of Electrocardiography - Progress through Technology; S. L. Barron, The development of the electrocardiograph in Great Britain, British Medical Journal 1:720, 25 March 1950) to measure the human electrocardiogram according to the standards developed by Einthoven.

Image by /Wikimedia

Schematic diagram of normal sinus rhythm for a human heart as seen on ECG.

Created by Agateller (Anthony Atkielski), converted to svg by atom.

Limb leads

!Original: MoodyGrooveVector: Twisp This SVG diagram includes elements that have been taken or adapted from this diagram: Wikicouple.svg. /Wikimedia

Precordial leads in ECG

Mikael Häggström/Wikimedia

Limb leads of EKG

Npatchett/Wikimedia

Spatial orientation of EKG leads

Npatchett

Animation of ECG Limb Leads and Electrical Conduction Through the Heart

10ebyu10e/Wikimedia

Willem Einthoven ECG

/Wikimedia

Treatment

Dexamethasone is a class of corticosteroids

Image by Mx. Granger/Wikimedia

Dexamethasone is a class of corticosteroids

Five dexamethasone tablets, 4mg each.

Image by Mx. Granger/Wikimedia

How Might Polymyositis Be Treated?

The treatment of polymyositis is based on the signs and symptoms present in each person. Although there is currently no cure, symptoms of the disease may be managed with the following:

Medications such as corticosteroids, corticosteroid-sparing agents, or immunosuppressive drugs
Physical therapy to improve muscle strength and flexibility
Speech therapy to address difficulties with swallowing and speech
Intravenous immunoglobulin: an infusion of healthy antibodies that are given to block damaging autoantibodies that attack the muscle

Source: Genetic and Rare Diseases (GARD) Information Center

Additional Materials (1)

Polymyositis Treatment : Johns Hopkins Myositis Center

Video by Johns Hopkins Rheumatology/YouTube

5:43

Polymyositis Treatment : Johns Hopkins Myositis Center

Johns Hopkins Rheumatology/YouTube

Prognosis

Treatment and Prognosis varies depending on the type of condition and the age of symptom onset.

Image by 4144132

Treatment and Prognosis varies depending on the type of condition and the age of symptom onset.

Prognosis varies depending on the type of MND and the age of symptom onset.

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What Is the Long-Term Outlook for People with Polymyositis?

If the treatment for polymyositis is not effective, affected individuals may develop significant disability. In rare cases, people with severe and progressive muscle weakness may develop respiratory failure or pneumonia. Difficulty swallowing may cause weight loss and malnutrition. Individuals with polymyositis may be more likely to develop other autoimmune diseases, cancer, or osteoporosis.

Source: Genetic and Rare Diseases (GARD) Information Center

Additional Materials (1)

Living with Polymyositis : Johns Hopkins Myositis Center

Video by Johns Hopkins Rheumatology/YouTube

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Living with Polymyositis : Johns Hopkins Myositis Center

Johns Hopkins Rheumatology/YouTube

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Polymyositis

Polymyositis is a type of inflammatory myopathy, which refers to a group of muscle diseases characterized by chronic muscle inflammation and weakness. The disease is more common among women and among black individuals. Learn about causes, symptoms and treatment options.

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