Decompression Sickness

Decompression sickness (DCS) is a condition that occurs when divers come back to the surface too quickly after being deep under water. It is caused by the formation of nitrogen bubbles in the blood stream and, in the worst cases, can cause death.

Depressive Disorders

Depressive disorders are mental illnesses characterized by deep, long-lasting feelings of sadness or despair. The patient may also lose interest in things that were once pleasurable.

Diabetes Mellitus

Diabetes mellitus (pronounced DI-uh-BEE-teez MEH-luh-tuss) is a condition in which the body's cells are no longer able to utilize blood sugar. Blood sugar is the fuel that cells use to make energy.

Down's Syndrome

Down's syndrome is the most common cause of mental retardation (see mental retardation entry) and malformation in newborns. It occurs because of the presence of an extra chromosome.


Dyslexia is a learning disability (see learning disorders entry) characterized by problems with reading, spelling, writing, speaking, or listening. In many cases, dyslexia appears to be hereditary.


An earache is discomfort or pain caused by an infection of the ear. The medical term for an ear infection is otitis (pronounced oh-TI-tuss).


Emphysema is a respiratory disorder characterized by problems in breathing. The disorder is caused by the enlargement of air sacs in the lungs.


Encephalitis (pronounced in-seh-fuh-LIE-tess) is an inflammation of the brain. It may be caused by a number of different factors.


Epilepsy is a seizure disorder. A seizure is an event that involves loss of consciousness and motor (muscular) control.

Flesh-Eating Disease

Flesh-eating disease is more properly called necrotizing fasciitis (pronounced nek-ro-TIZE-ing FASS-ee-i-tiss). The disease is caused by a rare bacterium that destroys tissues lying beneath the skin.

Food Poisoning

Food poisoning is a general term for health problems caused by eating contaminated food. Food may be contaminated by bacteria, viruses, toxins (poisons) from the environment, or toxins within the food itself.

Fractures, Sprains, and Strains

Fractures, sprains, and strains are injuries caused to bones, ligaments, joint capsules, or muscles. A joint capsule consists of all the tissues that hold a joint together.


Frostbite is damage to the skin and other tissue caused by freezing. The term frostnip is sometimes used for a mild form of frostbite.


Glaucoma is a disorder of the eye in which the optic nerve is damaged. The optic nerve carries light messages from the eye to the brain.

Hantavirus Infections

Hantavirus infections are caused by a group of viruses known as hantaviruses. These viruses cause two serious illnesses in humans.

Hay Fever

Hay fever is an inflammation of the nasal passages. It is an allergic reaction to substances present in the air.

Head Injury

Head injury refers to any damage to the scalp, skull, or brain. There are two general categories of head injuries: closed and penetrating.


A headache is a pain in the head. A headache can be caused by some other physical disorder, or it may be a disorder in and of itself.

Hearing Loss

Hearing loss is any reduction in a person's ability to detect sound.

Heart Attack

A heart attack is caused by the death of, or damage to, part of the heart muscle. Heart attacks usually occur because the supply of blood to the heart muscle is greatly reduced or stopped.

Heart Murmur

A heart murmur is an abnormal extra sound made when the heart beats. The sound is produced by blood moving through the heart and its valves.

Heat Disorders

Heat disorders are a group of illnesses caused by prolonged exposure to hot temperatures, restricted fluid intake, or failure of the body's ability to regulate its temperature. The general term used for heat disorders is hyperthermia (pronounced hi-per-THUR-mee-uh).


Hemophilia (pronounced hee-muh-FIH-lee-uh) is a genetic disorder that often results in excessive bleeding. The condition can range from mild to severe.

Hemorrhagic Fevers

Hemorrhagic fevers (pronounced heh-meh-RA-jik) are a group of diseases caused by viruses. They occur throughout the world, but are most common in tropical areas.


Hepatitis is an inflammation of the liver. At least six forms of hepatitis are now recognized.


Hernia is a general term for a bulge or protrusion of an organ through a part of the body in which it is usually contained.

Herpes Infections

Herpes infections are a group of diseases caused by a herpes virus. There are eight different herpes viruses that can infect humans.

Hodgkin's Disease

Hodgkin's disease is a cancer of the lymphatic (pronounced lim-FAT-ic) system. The lymphatic system consists of blood vessels, tissues, and other structures that carry lymph (pronounced limf) through the body.


Hypertension is the medical name for high blood pressure.


Hypoglycemia (pronounced HI-po-gli-seem-ee-ah) means low blood sugar. The main fuel used by cells to produce energy is a type of sugar called glucose.


Hypothermia (pronounced hi-po-ther-mee-ah) occurs when the body temperature falls below 95°F (35°C). The condition is often fatal.

The Content is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of Content found on the Website.