Macrocephaly is a condition in which the head is larger than normal.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a diagnostic imaging procedure that uses radio waves, a magnetic field, and a computer to generate images of the anatomy.


Malnutrition is a condition that develops when the body does not get the proper amount of protein, energy (calories), vitamins, and other nutrients it needs to maintain healthy tissues and organ function.


Malocclusion is the misalignment of the upper and lower teeth when biting or chewing.

Marfan Syndrome

Marfan syndrome is an inherited disorder of the connective tissue that causes abnormalities of a child's eyes, cardiovascular system, and musculoskeletal system. It is named for the French pediatrician, Antoine Marfan (1858-1942), who first described it in 1896.

Massage Therapy

Massage therapy is the scientific manipulation of the soft tissues of the body, consisting primarily of manual (hands-on) techniques such as applying fixed or movable pressure, holding, and moving muscles and body tissues.


Mastoiditis is a bacterial infection of the air cells in the mastoid bone of the skull. Mastoiditis most commonly affects children.


Masturbation is the erotic stimulation of one's own genitals for pleasure.

Maxillofacial Trauma

Maxillofacial trauma refers to any injury to the face or jaw caused by physical force, the presence of foreign objects, animal or human bites, or burns.


Measles is an infection caused by a virus, which causes an illness displaying a characteristic skin rash known as an exanthem. Measles is also sometimes called rubeola, five-day measles, or hard measles.


Meningitis is a serious inflammation of the meninges, the membranes (lining) that surround the brain and spinal cord. It can be of bacterial, viral, or fungal origin.

Meningococcal Meningitis Vaccine

The meningococcal meningitis vaccine is given by injection (shots) to provide immunization against meningococcal disease and meningitis caused by the bacterium Neisseria meningitides.


Meningococcemia is the presence of meningococcus in the bloodstream. Meningococcus, a bacteria formally called Neisseria meningitidis, can be one of the most dramatic and rapidly fatal of all infectious diseases.


Menstruation is the vaginal bleeding that occurs in adolescent girls and women as a result of hormonal changes. It normally happens in a predictable pattern, once a month.

Mental Retardation

Mental retardation is a developmental disability that first appears in children under the age of 18. It is defined as an intellectual functioning level (as measured by standard tests for intelligence quotient) that is well below average and significant limitations in daily living skills (adaptive functioning).


The generic name for the drug Ritalin, the most commonly prescribed medication for treating children with attention-deficit hyperactivity disorder (ADHD).

Mineral Deficiency

Mineral deficiency is a reduced level of any of the minerals essential to human health. An abnormally low mineral concentration is usually defined as a level that may impair a function dependent on that mineral.

Mineral Toxicity

The term mineral toxicity refers to a condition in which the concentration in the body of any one of the minerals necessary for life is abnormally high, and which has an adverse effect on health.


Minerals are inorganic nutrients. That is, they are materials found in foods that are essential for growth and health and do not contain the element carbon.

Minnesota Multiphasic Personality Inventory

The Minnesota Multiphasic Personality Inventory (MMPI-2; MMPI-A) is a written psychological assessment, or test, used to diagnose mental disorders.

Minority Health

Minority health addresses the special medical and health needs associated with specific ethnic and other minority groups.

Mitochondrial Disorders

Mitochondrial disorders, also called mitochondrial cytopathies, are a diverse group of diseases caused by damage to small structures found in human cells that are essential in converting food to energy. The result is decreased energy production and associated symptoms.

MMR Vaccine

MMR vaccine is a combined vaccine to protect children against measles, mumps, and rubella, which are dangerous and potentially deadly diseases. Alternative names are rubella vaccination, mumps vaccination, vaccine-MMR.


A mole (nevus) is a pigmented (colored) spot on the outer layer of the skin (epidermis).

Mood Disorders

Mood disorders are mental disorders characterized by periods of depression, sometimes alternating with periods of elevated mood.

Moral Development

Moral development is the process throught which children develop proper attitudes and behaviors toward other people in society, based on social and cultural norms, rules, and laws.

Motion Sickness

Motion sickness is uncomfortable dizziness, nausea, and vomiting that people experience when their sense of balance and equilibrium is disturbed because their brain cannot make sense of conflicting information about their body's location in space and motion in their environment.

Movement Disorders

Movement disorders are a group of diseases and syndromes affecting the ability to produce and control bodily movements.


Mucopolysaccharidosis (MPS) is a general term for many different related inherited disorders that are caused by the accumulation of mucopolysaccharides in body tissues. This accumulation interferes with the individual's development.

Multicultural Education/Curriculum

Multicultural education describes a system of instruction that attempts to foster cultural pluralism and acknowledges the differences between races and cultures. It addresses the educational needs of a society that contains more than one set of traditions, that is a mixture of many cultures.

Multiple Endocrine Neoplasia Syndromes

The multiple endocrine neoplasia (MEN) syndromes are three related inherited disorders affecting the thyroid and other hormone producing (endocrine) glands of the body. Before the early 2000s, MEN was called familial endocrine adenomatosis.

Multiple Pregnancy

Multiple pregnancy, usually referred to as multiple gestation, is one in which more than one fetus develops simultaneously in the mother's womb.


Mumps is a relatively mild short-term viral infection of the salivary glands that usually occurs during childhood.

Munchausen Syndrome

Munchausen syndrome is a psychiatric disorder that causes an individual to self-inflict injury or illness or to fabricate symptoms of physical or mental illness in order to receive medical care or hospitalization. In a variation of the disorder, Munchausen by proxy (MSBP), an individual, typically a mother, intentionally causes or fabricates illness in a child or other person under her care.

Muscle Spasms and Cramps

Muscle spasms and cramps are spontaneous, often painful muscle contractions.

Muscular Dystrophy

Muscular dystrophy is the name for a group of inherited disorders in which strength and muscle bulk gradually decline. Nine types of muscular dystrophies are generally recognized.


Mutism is a rare childhood condition characterized by a consistent failure to speak in situations where talking is expected.

Myers-Briggs Type Indicator

The Myers-Briggs Type Indicator (MBTI) is a widely used personality inventory, or test, employed in vocational, educational, and psychotherapy settings to evaluate personality type in adolescents and adults age 14 and older.


Myopathies are diseases of skeletal muscle that are not caused by nerve disorders. These diseases cause the skeletal or voluntary muscles to become weak or shrunken (atrophied).


Myopia, or nearsightedness, is a condition in which objects in the distance are blurred either because the eye is too long or too strong. It is the result of both environmental and genetic factors.

Myotonic Dystrophy

Myotonic dystrophy is a progressive disease in which the muscles are weak and slow to relax after contraction.

Myringotomy and Ear Tubes

Myringotomy is a surgical procedure in which a small incision is made in the eardrum (the tympanic membrane), usually in both ears. The word comes from myringa, modern Latin for drum membrane, and tomē, Greek for cutting.