Learn the terms and definitions helpful to know when thinking about myositis, diagnosis, complications and treatment.

Alternative therapy

Any therapy used in place of or in addition to conventional or more traditional treatments. (See complementary therapy.)

Amyopathic dermatomyositis

Dermatomyositis that involves the skin only without muscle symptoms.


A protein produced by the body that acts against an antigen (a substance foreign to the body, such as germs) in an immune response. In a typical immune response, immune cells identify antigens as invaders and stimulate the formation of antibodies to react with the foreign cells and make them harmless.


A foreign protein that stimulates an immune response in the body. An immune response is the body’s reaction to a foreign substance in order to keep it from harming the body.

Anti-Jo-1 antibody

A myositis-specific autoantibody that is associated with antisynthetase syndrome.


A type of medicine that acts against diseases with inflammation or pain in muscles or joints. Also called disease-modifying antirheumatic drugs (DMARDs). Methotrexate and hydroxychloroquine (Plaquenil) are antirheumatic drugs.

Antisynthetase syndrome

A rare condition involving the presence of antisynthetase autoantibodies in the blood and associated with interstitial lung disease, dermatomyositis, polymyositis, and other autoimmune diseases.


Inflammation or swelling of the joints.


Inhaling or breathing in food or other substances into the larynx below the vocal chords toward your lungs. This can lead to aspiration pneumonia, an often serious infection in the lungs caused by these bits of inhaled substances.


A protein produced by the immune system that is directed against one or more of a person’s own proteins.

Autoimmune disease

A disease in which the body’s immune system, which normally fights off infections and foreign substances, is misdirected and mistakenly attacks its own healthy tissues causing inflammation. In myositis, the immune system attacks otherwise healthy muscles and blood vessels.

Biologics (biologic response modifiers)

Pharmaceutical compounds derived from natural, living sources, in contrast to most drugs that are chemically synthesized. Biologics include vaccines, blood and blood components (such as IVIg), gene therapies, monoclonal antibodies, and other products.


A test in which a small piece of muscle, skin, or other tissue is removed to view under the microscope, looking for abnormalities that may help in diagnosing a condition.


Hard, often painful lumps of calcium that form under the skin’s surface, especially in dermatomyositis.


Clouding of the lens of the eye that blocks light and distorts vision. Cataracts can be a side effect of prednisone and other medicines used to treat myositis. Regular eye exams are encouraged.

Complementary therapy

Any therapy used in addition to treatment prescribed by your physician. Complementary approaches to health may include exercise, yoga, hypnosis, movement therapies, meditation, acupuncture, dietary supplements, other botanical products, homeopathy, special diets, and more.


A permanent shortening of a muscle or tendon, causing a joint to remain bent. Range-of-motion exercises may be prescribed to help prevent or improve contractures.

Conventional therapy

Traditional treatments that are most commonly prescribed by physicians. For many people with myositis, for example, conventional therapy includes prednisone and/or other immunosuppressant medications.

Corticosteroids (steroids)

Medications aimed at slowing the immune system, reducing inflammation, and relieving swelling, itching, and discomfort. Prednisone and Solu-Medrol are corticosteroid medications.

Disease activity

What is currently and actively going on with the disease, such as muscle weakness and skin rash. (See disease damage.)

Disease damage

Long-term effects or changes caused by the disease or medication side effects and not by current disease activity. (See disease activity.)

Disease-modifying antirheumatic drugs (DMARDs)

A category of drugs used to treat rheumatic diseases to slow the progression of the disease.


Located away from the center of the body, such as muscles in the fingers, hands, and feet. (See also proximal.)


Difficulty swallowing.


Problems with the voice, often resulting in weaker or hoarse vocal sounds.


The effectiveness of a particular therapy in treating the disease or condition for which it is being tested or prescribed.

Electromyogram (EMG)

A diagnostic test to evaluate and record the electrical activity produced by skeletal muscles.

First-line treatment or therapy

Medication considered the first or best choice for treating a certain condition.


Return of past symptoms or increase in current symptoms after a period of remission or slower disease activity. This may occur when tapering medication too quickly or overexerting oneself through exercise or stress. People with dermatomyositis may also notice flares with sun exposure.

Generic drug

A medication created to be equivalent to a brand-name drug. Generics usually cost less than their brand-name counterparts.

Gottron’s sign (Gottron’s papules)

Red, sometimes scaly, eruptions on the knuckles, elbows, and knees. Gottron’s papules are a characteristic skin symptom of dermatomyositis.

Heliotrope rash

Blue-purple discoloration on the upper eyelids with swelling. Heliotrope rash is a characteristic skin symptom of dermatomyositis.


Of unknown cause. Idiopathic inflammatory myopathy (IIM) is the broader medical term used to describe all forms of autoimmune myositis.

Immune response

The body’s response to the presence of a foreign substance in order to keep it from harming the body. Inflammation or swelling is one type of immune response.

Immune system

A network of cells, tissues, and organs that work together to defend the human body against attacks by harmful foreign invaders, such as bacteria, parasites, fungi, and viruses that can cause infections.

Immunoglobulin (gamma globulin or immune globulin)

A substance made from human plasma obtained from donated blood that contains antibodies and is used to treat certain diseases, including some forms of myositis. Immune globulin can be given intravenously (IVIg) or subcutaneously (SCIg).

Immunosuppressant (immune suppressant)

A drug that suppresses or reduces the strength of the body’s immune response. Immune suppressant drugs are often used to treat autoimmune disorders such as myositis.


Part of the immune system’s natural response to heal an injury or fight an infection. Typical signs of inflammation include heat, pain, redness, swelling, and loss of function.

Integrative therapy

An approach to healing that uses both conventional medical treatments and complementary methods in a coordinated way.

Interstitial lung disease (ILD)

A group of lung diseases causing scarring and thickening of the tissues around the air sacs of the lungs. Except in IBM, ILD is the most common and serious complication of IIMs.


A method for giving medication or fluids through a needle directly into the vein.


A disorder that causes problems in the way the body uses and stores fat. This can be associated with JDM.


Affecting only a part of the body where a treatment is applied, as opposed to the whole body. Local treatments include creams applied to a DM skin rash.


A white blood cell that is a part of the immune response.

Magnetic resonance imaging (MRI)

A medical imaging test used to form pictures of the organs and processes in the body in both health and disease. MRI is used to detect inflammation in muscles in myositis.

Maintenance dose

The smallest amount of medication a person needs to keep symptoms from returning or worsening.

Malar rash

A butterfly-shaped rash on the cheeks and bridge of the nose often seen in dermatomyositis.

Manual muscle testing (MMT)

Test of a person’s muscle strength or ability of the muscle to move a part of the body against resistance. When a doctor or therapist tests muscle strength in individual muscles, the results can show which muscles are weak and the pattern of the weakness. MMT is often performed throughout the disease course to follow the patient’s progress over time.

Mechanic’s hands

Roughened and cracked skin on the sides of the fingers and palms, resulting in irregular, dirty-appearing lines that resemble those of a manual laborer. Mechanic’s hands are a characteristic skin symptom of antisynthetase syndrome.

Mixed connective tissue disease (MCTD)

An autoimmune disorder in which there are signs and symptoms of multiple connective tissue diseases, such as lupus, scleroderma, and polymyositis.

Monoclonal antibody medications

Compounds that use natural immune system functions to target certain cells in the body to treat disease. These compounds are called biologics (rather than drugs) and have names that end in -mab, such as rituximab and tocilizumab.

Muscle enzymes

Proteins found mostly in muscle tissue cells. When muscle cells are injured (as they are through the inflammation of myositis), the cells break open and leak enzymes into the bloodstream. Blood tests are used to measure the levels of these enzymes in the blood to help doctors determine what may be happening and also how well you are responding to treatment.

Myositis-associated autoantibodies (MAA)

Proteins found in the blood of myositis patients as well as in the blood of patients with other autoimmune diseases. These autoantibodies are not specific to myositis, but they can help guide treatment and understand the likely course of the disease. (See myositis-specific autoantibodies.)

Myositis-specific autoantibodies (MSA)

Proteins found only in the blood of myositis patients, therefore these autoantibodies are specific to myositis. Anti-Jo-1 and anti-SRP are myositis-specific autoantibodies. Because they are unique to myositis, finding one of these autoantibodies in the blood is diagnostic for myositis. The specific type of MSA also helps guide treatment and understand the likely course of the disease. (See myositis-associated autoantibodies.)

Occupational therapy (OT)

Therapy designed to restore or maintain a patient’s ability to perform tasks used in daily living, often through developing ways to modify or adapt activities.


A condition in which bone mineral density is lower than normal. It may be a precursor to osteoporosis.


A disease characterized by decreased bone density, resulting in thinning of bone tissue and decreased mechanical strength.

Overlap syndrome

An disease in which a person has symptoms of two or more autoimmune conditions. The patient’s symptoms must meet the diagnostic criteria of all of the diseases to be considered overlap. Some common diseases that overlap with myositis are rheumatoid arthritis, lupus, scleroderma, and Sjogren’s disease.

Physical therapy (physiotherapy or PT)

Treatment of a disease through physical activity with goals of restoring and/or maintaining functional activities.

Prospective study

A type of research that follows a group of patients over time, looking for outcomes, such as the development of disease, that occur during the study period and can be associated with suspected risk or protection factor(s). (See retrospective study.)


Located toward the center of the body, such as muscles of the neck, shoulders, upper arms, and upper legs. (See distal.)

Range-of-motion (ROM)

The full amount of movement at each joint. ROM exercises focus on maintaining flexibility and movement in the joints.

Raynaud’s phenomenon (Raynaud’s syndrome)

A condition in which spasms of the arteries cause episodes of reduced blood flow, typically involving the fingers and toes. The episodes last several minutes to several hours and cause the affected part to feel numb and cold and to turn white and then blue. Raynaud’s is a characteristic symptom of antisynthetase syndrome.


Resistant or unresponsive to treatment.


Return of symptoms after a period of remission or stable disease activity.


A state or period during which a patient shows no symptoms of disease after being off all medications.

Retrospective study

A type of research that gathers data from the past on a group of patients to identify exposures to suspected risk or protection factors in relation to a certain outcome, such as disease susceptibility or medication effectiveness.

Rheumatic disease

An umbrella term used to describe chronic conditions affecting the joints and/or connective tissue. Rheumatology is the medical specialty concerned with the study, diagnosis, and treatment of rheumatic diseases. Myositis is considered a rheumatic disease.

Rimmed vacuoles

Small areas of membrane encased deterioration in the muscle cells in inclusion body myositis and other muscle disorders.

Second-line treatment or therapy

Medication chosen after a patient fails to respond to the first medication given or when side effects from the first medication are too great. Methotrexate is often a second-line treatment for myositis after initial treatment with prednisone.

Shawl sign

A widespread, flat, red rash that appears on the upper back, shoulders, and back of the neck.

Side affect

An unwanted reaction to a medicine. For example, weight gain is a common side effect of corticosteroids.


Objective evidence or finding of a disease that can be seen and understood by a doctor.

Silent aspiration

Occurs when foods or liquids are breathed into the lungs but do not produce the typical reaction of coughing. With silent aspiration, patients do not realize they are breathing in particles of food or liquids.

Steroid myopathy (type 2 muscle fiber atrophy)

Muscle weakness caused by damage to muscle fibers either by excessive intake of corticosteroid medication or hormonal abnormalities.


Subjective evidence or personal findings of a disease as experienced and recognized by the patient.


Treatment that affects the body as a whole, such as medications taken orally or intravenously.


The process of gradually lowering the dosage of medication to reach a maintenance dose or to stop the medication completely. Corticosteroids, in particular, require a tapering schedule to allow the body to adjust to the lower dosage.


Break in the skin or mucous membrane.


Inflammation of the blood vessels causing restricted blood flow. Vasculitis is believed to be the underlying cause of dermatomyositis.