Ectopic. Occuring in the wrong place in the body, such as the development of an impregnated egg outside the cavity of the uterus; or, a cardiac beat originating elsewhere other than at the sinoatrial node.

EDS. Acronym for excessive daytime sleepiness.

EKG or ECG. Electrocardiogram, a test that prints out a graphic record of a person’s heart beat.

Endocrine system. The body system that secretes hormones that allow the body perform many of its functions.

Epidemiology. The study of the distribution of health-related states (for a specific disease, like myotonic dystrophy) or events in specified populations.

Esophagus. The portion of the digestive canal between the pharynx and stomach.

Expansion. On FAQ's page, referring to enlargement of the myotonic dystrophy genetic mutation, or abnormality, as it passes to offspring; also refers to the enlargement of mutations within a given organ or system over the life of an affected individual (see somatic mosaicism); happens often in myotonic dystrophy.