Galactosemia is an inherited disease in which the body is unable to metabolize the simple sugar galactose, which is found primarily in dairy products but is also produced by the body. If left unaddressed, galactose can increase to toxic levels in the body and may lead to damage of the liver, central nervous system, and various other body systems.


Youth gangs are variously defined in the social science and criminal justice literature. They are commonly understood to be a loosely-organized association of socially excluded, alienated, or bigoted individuals acting together within a fluid structure with informal leadership.


Gastroenteritis is an inflammation of the digestive tract, particularly the stomach, and large and small intestines. Viral and bacterial gastroenteritis are intestinal infections associated with symptoms of diarrhea, abdominal cramps, nausea, and vomiting.

Gastroesophageal Reflux Disease

Gastroesophageal reflux disease (GERD) is a gastric disorder which causes stomach acids to back up into the esophagus, the tube leading from the mouth to the stomach. This action causes pain, which is often called heartburn.

Gender Constancy

A child's realization that gender is fixed and does not change over time.

Gender Identity

Gender identity is a person's sense of identification with either the male or female sex, as manifested in appearance, behavior, and other aspects of a person's life.

Gross Motor Skills

Gross motor skills are the abilities required in order to control the large muscles of the body for walking, running, sitting, crawling, and other activities.

Growth Hormone Tests

Growth hormone tests measure the levels of specific hormones that regulate human growth. These hormone levels are measured in blood serum samples obtained by venipuncture.


Handedness is the preferred use of the right hand, the left hand, or one or the other depending on the task.

Hand-Eye Coordination

Hand-eye coordination is the ability of the vision system to coordinate the information received through the eyes to control, guide, and direct the hands in the accomplishment of a given task, such as handwriting or catching a ball. Hand-eye coordination uses the eyes to direct attention and the hands to execute a task.

Hand-Foot-Mouth Disease

Hand-foot-mouth disease is an infection of young children in which characteristic fluid-filled blisters appear on the hands, feet, and inside the mouth.

Head Injury

Head injury is an injury to the scalp, skull, or brain. The most important consequence of head trauma is traumatic brain injury.

Head Start Programs

Head Start is a federally funded preschool program that provides comprehensives services to both low-income children and their families.


A headache involves pain in the head that can arise from many disorders or may be a disorder in and of itself.

Hearing Impairment

Hearing impairment is the temporary or permanent loss of some or all hearing in one or both ears.

Heart Murmurs

A heart murmur is an abnormal swishing or whooshing sound made by blood moving through the heart, heart valves, or blood vessels near the heart during the heartbeat cycle. It is heard through a stethoscope by a physician.

Heat Disorders

Heat disorders are a group of physically related illnesses caused by prolonged exposure to hot temperatures, restricted fluid intake, or failure of temperature regulating mechanisms of the body. Disorders of heat exposure include heat cramps, heat exhaustion, and heat stroke (also called sunstroke).

Heavy Metal Poisoning

Heavy metal poisoning is the toxic accumulation of heavy metals in the soft tissues of the body.

Heimlich Maneuver

The Heimlich maneuver is an emergency technique for removing a foreign object lodged in the airway that is preventing a child or an adult from breathing.


Hemophilia is a coagulation disorder arising from a genetic defect of the X chromosome; the defect can either be inherited or result from spontaneous gene mutation. In each type of hemophilia (hemophilias A, B, and C), a critical coagulation protein is missing, causing individuals to bleed for long periods of time before clotting occurs.

Hemophilus Infections

Hemophilus infections, most of which are due to Haemophilus influenzae infections, are a group of contagious diseases that are caused by a bacterium and affect only humans. Some hemophilus infections are potentially fatal.

Hepatitis A

Hepatitis A is a liver disease caused by the hepatitis A virus (HAV).

Hepatitis B

Hepatitis B is a liver disease caused by the hepatitis B virus (HBV).

Hepatitis B Vaccine

The hepatitis B vaccine (HBV or HepB) is an injection that protects children from contracting hepatitis B, a serious disease caused by the hepatitis B virus.

Hereditary Fructose Intolerance

Hereditary fructose intolerance is a metabolic disorder in which the small intestine cannot process fructose (fruit sugar) into a source of energy because of an enzyme deficiency that prevents fructose absorption.

Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia is a condition characterized by abnormal blood vessels which are delicate and prone to bleeding. Hereditary hemorrhagic telangiectasia is also known as Osler-Weber-Rendu disease.


A hernia is the protrusion of an organ through the structure or muscle that usually contains it.

Herpes Simplex

Herpes is an infection caused by a herpes simplex virus 1 or 2, and it primarily affects the mouth or genital area.

Hib Vaccine

The Hib vaccine is an injection that helps protect children from contracting infections due to Haemophilus influenzae type B (Hib), a bacterium that is capable of causing serious illness and potential death in children under age five.

High-Risk Pregnancy

Although as of 2004 there was no formal or universally accepted definition of a "high-risk" pregnancy, it is generally thought of as one in which the mother or the developing fetus has a condition that places one or both of them at a higher-than-normal-risk for complications, either during the pregnancy (antepartum), during delivery (intrapartum), or following the birth (postpartum).

Hirschsprung's Disease

Hirschsprung's disease, also known as congenital megacolon or aganglionic megacolon, is an abnormality in which certain nerve fibers are absent in segments of the bowel, resulting in severe bowel obstruction.

Histiocytosis X

Histiocytosis X is a generic term that refers to an increase in the number of histiocytes, a type of white blood cell that acts as a scavenger to remove foreign material from the blood and tissues. Research that demonstrated Langerhans cell involvement as well as histiocytes led to a proposal that the term Langerhans cell histiocytosis (LCH) be used in place of histiocytosis X.

HIV Infection and AIDS

Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immune deficiency syndrome (AIDS) by infecting helper T cells of the immune system. The most common serotype, HIV-1, is distributed worldwide, while HIV-2 is primarily confined to West Africa.


Hives is an allergic skin reaction causing localized redness, swelling, and itching.

Home Schooling

Home schooling is the process of educating school-aged children at home rather than at a school. As of the early 2000s, it is perhaps one of the fastest growing trends in education in the United States.

Homosexuality and Bisexuality

Homosexuality is the consistent sexual and emotional attraction, including fantasy, interest, and arousal to a person of the same sex. Bisexuality is the sexual and emotional attraction to members of both sexes.


Patients are admitted to the hospital for a variety of reasons, including scheduled tests, procedures, or surgery; emergency medical treatment; administration of medication; or to stabilize or monitor an existing condition.

Human Bite Infections

Human bite infections are potentially serious injuries that develop when a person's teeth break the skin of the hand or other body part and introduce saliva containing disease organisms below the skin surface.


Hydrocephalus is an abnormal expansion of cavities, called ventricles, within the brain, which is caused by an abnormally large accumulation of cerebrospinal fluid (CSF).


Hyperglycemia is a complex metabolic condition characterized by abnormally high levels of blood sugar (blood glucose) in circulating blood, usually as a result of diabetes mellitus (types 1 and 2), although it can sometimes occur in cystic fibrosis and near-drowning (submersion injury).


Hyperhidrosis is a medical condition characterized by excessive sweating in the armpits, palms, soles of the feet, face, scalp, and/or torso.

Hyper-IgM Syndrome

Hyper-IgM syndrome is a primary immunodeficiency disorder in which the child's body fails to produce certain specific types of antibodies. The term primary means that the disorder is present from birth, in contrast to secondary immunodeficiencies (such as AIDS), which are acquired later in life by previously healthy persons.


Hypertension is high blood pressure. Blood pressure is the force of blood pushing against the walls of arteries.


Hyperthyroidism is the overproduction of thyroid hormones by an overactive thyroid.


Hypoglycemia is a condition characterized by low blood sugar, or abnormally low levels of glucose in the blood.


Hypogonadism is the condition in which the production of sex hormones and germ cells (sperm and eggs) is inadequate.


Hypospadias is a congenital defect of the penis in which the urinary tract opening, or urethral meatus, is abnormally located away from the tip of the penis.


Hypothyroidism, or underactive thyroid, develops when the thyroid gland fails to produce or secrete as much thyroxine (T4) and triiodothyonine (T3) as the body needs. Because these thyroid hormones regulate such essential functions as heart rate, digestion, physical growth, and mental development, an insufficient supply of this hormone can slow metabolic processes, damage organs and tissues in every part of the body, and lead to life-threatening complications.


Hypotonia, or severely decreased muscle tone, is seen primarily in children. Low-toned muscles contract very slowly in response to a stimulus and cannot maintain a contraction for as long as a normal muscle.