Duchenne Muscular Dystrophy:Glossary of Terms

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Adeno-associated virus (AAV)

A naturally occurring virus that is modified for use in gene therapy to carry new DNA to cells. AAV is not known to cause illness in humans. See Viral vector.

Adverse event

A negative change in health associated with treatment with an approved or investigational therapy.


The basic building blocks of your body’s tissues that carry on the essential functions of life. Cells come in a variety of shapes and sizes depending on the tissue (muscle, skin, liver, etc.) and are specialized to perform a variety of different jobs within the body. Each cell contains its own machinery (called organelles) to do the work needed to keep the cell healthy and functioning properly.

Clinical study

See Clinical trial.

Clinical trial

A scientific study of an investigational product (such as a drug or vaccine) to see whether it is safe and works as intended (efficacy), conducted in people who consent to be in the study. Regulatory agencies like the U.S. Food and Drug Administration (FDA) or European Medicines Agency (EMA) that review and approve new treatments, vaccines, etc. usually require that clinical trials be conducted in a series of phases:

  • Phase I clinical trials study an investigational product in humans for the first time. Typically Phase I clinical trials are small and focus on safety, side effects, dosage and delivery method, although many also test whether the drug may work as intended (efficacy).
  • Phase II clinical trials also study an investigational product’s safety and efficacy in a larger group of participants.
  • Phase III clinical trials typically confirm an investigational product’s efficacy and safety, and sometimes compare it against other therapies, in a large group of patients for a longer period of time.
  • Phase IV clinical trials are done after an investigational product has received approval from a regulatory agency and has been brought to market, further evaluating long term side effects, benefits and potential new uses for other conditions.

The genetic material that is passed from parent to child and provides the “blueprint” for making all the proteins in the body. The instructions in DNA are unique to an individual (except identical twins) and influence characteristics like eye color, height or risk of developing certain diseases.

Duchenne muscular dystrophy (Duchenne)

Duchenne muscular dystrophy is a genetic, muscle-wasting disease predominantly affecting boys with symptoms that usually manifest between three and five years of age. Duchenne is a progressive, irreversible and ultimately fatal disease that affects approximately one in every 3,500 to 5,000 live male births. Duchenne is caused by mutations in the dystrophin gene, which result in the absence or near-absence of dystrophin protein. Without functioning dystrophin and certain associated proteins, muscles suffer excessive damage from normal daily activities and are unable to regenerate, leading to the build-up of fibrotic, or scar, and fat tissue. There is no cure for Duchenne and, for the vast majority of patients, there are no satisfactory symptomatic or disease-modifying treatments.


A protein that is critical for maintaining the health of muscle cells and protecting them from injury when muscles contract and relax. In Duchenne muscular dystrophy, a defect in the gene for dystrophin results in the absence or near-absence of dystrophin protein in muscle.

European Medical Agency (EMA)

A regulatory agency of the European Union (EU). EMA is responsible for the scientific evaluation, supervision and safety monitoring of medicines in the EU. See www.ema.europa.eu for further information.

U.S. Food & Drug Administration (FDA)

A regulatory agency within the U.S. Department of Health and Human Services located in Washington, D.C. One of the FDA’s functions is to protect public health by assuring the safety, effectiveness, quality and security of drugs, vaccines and other biological products, as well as medical devices. See www.fda.gov for further information

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Information in a person’s DNA that provides instructions for making proteins that perform different functions in the cells of the body.

Gene therapy

Gene therapy is an experimental technique that uses genes to treat or prevent disease. The goal of gene therapy is to replace or correct missing or faulty genes. One gene therapy approach is called gene transfer. See Gene Transfer.

Gene transfer

A type of gene therapy in which a new, functional version of a gene is delivered to the body to make up for the faulty one that is causing disease.

Genetic disease

A disease caused by abnormalities in an individual’s genes.

Genetic testing

A type of medical test that identifies unique features of an individual’s genes, particularly those that might be associated with a disease.


A branch of medicine that deals with how we inherit characteristics and diseases.


The whole collection of DNA “blueprints” that provide the instructions for building and maintaining all the parts of the body.

Human body tissue

Different types of material that make up the body’s organs (liver, kidney, heart, etc.) and other parts of the body. Muscle is one type of tissue found throughout the body.

Immune system

A network of cells, tissues and organs that work together to protect the body against infection and illness. The immune system knows what is naturally a part of your body and reacts against anything that is foreign or abnormal, like bacteria, viruses, or cells that have turned into cancer.

Informed consent

The process of giving complete and clear information about a clinical trial to individuals who are thinking about participating, so they understand what is involved, including the potential risks, before they decide to participate.


To get your own unique set of genes from both of your parents.


The process of getting genes that were passed down from your parents.


Being whole and undamaged.

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Microdystrophin gene

An engineered gene that contains the instructions to make a smaller, functional form of dystrophin protein. Microdystrophin gene transfer is currently being researched as a possible gene therapy for Duchenne.

Monogenetic disease

A genetic disease caused by a mutation in one gene (mono means “single”). Diseases caused by just one abnormal gene can be promising targets for gene therapy.

Muscle biopsy

An operation to take out a piece of muscle for medical testing.

Muscular dystrophy

A broad name for all genetic diseases that cause muscle weakness.


A change in the information carried in genes. Some mutations are harmless but some can cause disease.

Nucleus (of the cell)

The part of the cell where the DNA “blueprints” (genes) are stored.


Components that make up the inner machinery of the cell and work together to keep the cell healthy and functioning properly.


Components of a cell that are made using the instructions in DNA and are assembled to build cells and make them work properly.

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RNA is the working copy of the DNA instructions that the body uses to make proteins in the cell. See Transcription and translation.

Skeletal muscle

Muscles that work together with our bones to make our body move and give it strength.


The first step in making a protein; the process of making a working RNA copy of the instructions in the original DNA “blueprint.”


The process of using the working RNA copy of the DNA instructions to build a specific protein.

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Viral vector

A virus that is used to carry and deliver new genes into living cells. See AAV.


A tiny particle made up of proteins and DNA or RNA that infects cells. See AAV.


Males have an X and Y chromosome, and females have two X chromosomes. In an X-linked genetic disease, the abnormal gene is on the X chromosome, so usually males are affected because they have just one X chromosome.