Marfan syndrome is an inherited disorder of the connective tissue that causes abnormalities of the patient's eyes, cardiovascular system, and musculoskeletal system. It is named for the French pediatrician, Antoine Marfan (1858–1942), who first described it in 1896. Marfan syndrome is sometimes called arachnodactyly, which means "spider-like fingers" in Greek, since one…
Marijuana (marihuana) Cannabis sativa L., also known as Indian hemp, is a member of the Cannabaceae or hemp family, thought to have originated in the mountainous districts of India, north of the Himalayan mountains. Two related species of cannabis are C. ruderalis, and C. indica, a variety known as Indian hemp. Indian hemp grows to a height of about 4 ft (1.2 m) and the seed coats have a marbled a…
Marriage counseling is a type of psychotherapy for a married couple or established partners that tries to resolve problems in the relationship. Typically, two people attend counseling sessions together to discuss specific issues. Marriage counseling is based on research that shows that individuals and their problems are best handled within the context of their relationships. Marriage counselors ar…
The Marshall-Marchetti-Krantz procedure surgically reinforces the bladder neck in order to prevent unintentional urine loss. The Marshall-Marchetti-Krantz procedure is performed to correct stress incontinence in women, a common result of childbirth and/or menopause. Incontinence also occurs when an individual involuntarily loses urine after pressure is placed on the abdomen (like during exercise, …
Massage therapy is the scientific manipulation of the soft tissues of the body for the purpose of normalizing those tissues and consists of manual techniques that include applying fixed or movable pressure, holding, and/or causing movement of or to the body. Generally, massage is known to affect the circulation of blood and the flow of blood and lymph, reduce muscular tension or flaccidity, affect…
Mastectomy is the surgical removal of the breast for the treatment or prevention of breast cancer. Mastectomy is performed as a surgical treatment for breast cancer. The severity of a breast cancer is evaluated according to a complex system called staging. This takes into account the size of the tumor and whether it has spread to the lymph nodes, adjacent tissues, and/or distant parts of the body.…
Mastitis is an infection of the breast. It usually only occurs in women who are breastfeeding their babies. Breastfeeding is the act of allowing a baby to suckle at the breast, in order to drink the mother's milk. In the process, unaccustomed to the vigorous pull and tug of the infant's suck, the nipples may become sore, cracked, or slightly abraded. This creates a tiny opening in th…
Mastocytosis is a disease characterized by the presence of too many mast cells in various organs and tissues. The body has a variety of free-roaming cell populations that function as immunogenic agents. Most immunogenic cells fall into the category of white blood cells, but some remain in tissues and are not found in the blood. Mast cells are such a group. Mast cells are found primarily in the ski…
Mastoidectomy is a surgical procedure to remove an infected portion of the bone behind the ear when medical treatment is not effective. This surgery is rarely needed today because of the widespread use of antibiotics. Mastoidectomy is performed to remove infected air cells within the mastoid bone caused by mastoiditis, ear infection, or an inflammatory disease of the middle ear (cholesteatoma). Th…
Mastoiditis is an infection of the spaces within the mastoid bone. It is almost always associated with otitis media, an infection of the middle ear. In the most serious cases, the bone itself becomes infected. The mastoid is a part of the side (temporal bone) of the skull. It can be felt as a bony bump just behind and slightly above the level of the earlobe. The mastoid has been described as resem…
Maxillofacial trauma refers to any injury to the face or jaw caused by physical force, foreign objects,or burns. Maxillofacial trauma includes injuries to any of the bony or fleshy structures of the face. Any part of the face may be affected. Teeth may be knocked out or loosened. The eyes and their muscles, nerves, and blood vessels may be injured as well as the eye socket (orbit), which can be fr…
Measles is an infection, caused by a virus, which causes an illness displaying a characteristic skin rash. Measles is also sometimes called rubeola, 5-day measles, or hard measles. Measles infections appear all over the world. Prior to the current effective immunization program, large-scale measles outbreaks occurred on a two to three-year cycle, usually in the winter and spring. Smaller outbreaks…
Meckel's diverticulum is a congenital pouch (diverticulum) approximately two inches in length and located at the lower (distal) end of the small intestine. It was named for Johann F. Meckel, a German anatomist who first described the structure. The diverticulum is most easily described as a blind pouch that is a remnant of the omphalomesenteric duct or yolk sac that nourished the early embr…
Mediastinoscopy is a surgical procedure that allows physicians to view areas of the mediastinum, the cavity behind the breastbone that lies between the lungs. The organs in the mediastinum include the heart and its vessels, the lymph nodes, trachea, esophagus, and thymus. Mediastinoscopy is most commonly used to detect or stage cancer. It is also ordered to detect infection, and to confirm diagnos…
Meditation is a practice of concentrated focus upon a sound, object, visualization, the breath, movement, or attention itself in order to increase awareness of the present moment, reduce stress, promote relaxation, and enhance personal and spiritual growth. Meditation benefits people with or without acute medical illness or stress. People who meditate regularly have been shown to feel less anxiety…
Medullary sponge kidney is a congenital defect of the kidneys where the kidneys fill with pools of urine. One of every 100 to 200 people have some form of this disease. The kidneys filter urine from the blood and direct it down tiny collecting tubes toward the ureters (ducts that carry urine from the kidney to the bladder). These tiny tubes gradually join together until they reach the renal pelvis…
Melioidosis is an infectious disease of humans and animals caused by a gram-negative bacillus found in soil and water. It has both acute and chronic forms. Melioidosis, which is sometimes called Pseudomonas pseudomallei infection, is endemic (occurring naturally and consistently) in Southeast Asia, Australia, and parts of Africa. It was rare in the United States prior to recent immigration from So…
Meniere's disease is a condition characterized by recurring vertigo (dizziness), hearing loss, and tinnitus (a roaring, buzzing or ringing sound in the ears). Meniere's disease was named for the French physician Prosper Meniere who first described the illness in 1861. It is an abnormality within the inner ear. A fluid called endolymph moves in the membranous labyrinth or semicircular…
Meningitis is a potentially fatal inflammation of the meninges, the thin, membranous covering of the brain and the spinal cord. Meningitis is most commonly caused by infection (by bacteria, viruses, or fungi), although it can also be caused by bleeding into the meninges, cancer, diseases of the immune system, and an inflammatory response to certain types of chemotherapy or other chemical agents. T…
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. A close-up image of a person's hand with meningococcemia. This disease is caused by the presence of meningococcus (Neisseria meningitidis) in the bloodstream. The organism can …
Menopause represents the end of menstruation. While technically it refers to the final period, it is not an abrupt event, but a gradual process. Menopause is not a disease that needs to be cured, but a natural life-stage transition. However, women have to make important decisions about "treatment," including the use of hormone replacement therapy (HRT). Many women have irregular peri…
Men's health is concerned with identifying, preventing, and treating conditions that are most common or specific to men. Men live on average seven years less than women; life expectancy in the United States is 72 years for men and 79 years for women. The reasons for this discrepancy are not completely understood. Men may have some genetic predisposition for lower life expectancy, as women t…
Anything that interferes with the normal menstrual cycle, causing pain, unusually heavy or light bleeding, or missed periods. Typically, a woman of childbearing age should menstruate every 28 days or so unless she's pregnant or moving into menopause. But numerous things can wrong with the normal menstrual cycle, some the result of physical causes, others emotional. These include amenorrhea,…
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). Mental retardation occurs in 2.5-3% of the general population. About 6-7.5 million menta…
A mental status examination (MSE) is an assessment of a patient's level of cognitive (knowledge-related) ability, appearance, emotional mood, and speech and thought patterns at the time of evaluation. It is one part of a full neurologic (nervous system) examination and includes the examiner's observations about the patient's attitude and cooperativeness as well as the patient&…
Metabolic acidosis is a pH imbalance in which the body has accumulated too much acid and does not have enough bicarbonate to effectively neutralize the effects of the acid. Metabolic acidosis, as a disruption of the body's acid/base balance, can be a mild symptom brought on by a lack of insulin, a starvation diet, or a gastrointestinal disorder like vomiting and diarrhea. Metabolic acidosis…
Metabolic alkalosis is a pH imbalance in which the body has accumulated too much of an alkaline substance, such as bicarbonate, and does not have enough acid to effectively neutralize the effects of the alkali. Metabolic alkalosis, as a disturbance of the body's acid/base balance, can be a mild condition, brought on by vomiting, the use of steroids or diuretic drugs, or the overuse of antac…
Methadone is a powerful narcotic drug in the same class as heroin. This class is known as the opioids. Methadone, formerly known as dolophine, is a psychoactive drug, meaning that it affects the mind or behavior. It belongs to the class of opioids, drugs that share some of the analgesic properties, and mimic the action of some of the body's naturally occurring chemicals called peptides, suc…
When excessive hemoglobin in the blood is converted to another chemical that cannot deliver oxygen to tissues, called methemoglobin. The molecule hemoglobin in the blood is responsible for binding oxygen to give to the body. When hemoglobin is oxidized to methemoglobin its structure changes and it is no longer able to bind oxygen. Hemoglobin is constantly under oxidizing stresses: however, normall…
Anophthalmia is the complete absence of an eye. Microphthalmia is an eye that has an abnormal smallness. Anophthalmia is caused by a defect in embryonic development. The total absence of an eye is extremely rare and often a clinical sign associated with a broad range of genetic disorders or, more commonly, a sporadic mutation. Sporadic transmission occurs in the affected individual due to a geneti…
Mifepristone is a pill that can be taken as an alternative to a surgical abortion. This medication is best-suited for ending early pregnancies. Women who are more than seven weeks pregnant (or 49 days since their last menstrual period) should not take mifepristone. Other reasons to avoid mifepristone include: use of an intrauterine device (IUD), ectopic pregnancy, use of blood thinners, bleeding d…
Migraine is a type of headache marked by severe head pain lasting several hours or more. Migraine is an intense, often debilitating type of headache. Migraines affect as many as 24 million people in the United States, and are responsible for billions of dollars in lost work, poor job performance, and direct medical costs. Approximately 18% of women and 6% of men experience at least one migraine at…
The term mineral deficiency means a condition where the concentration of any one of the minerals essential to human health is abnormally low in the body. In some cases, an abnormally low mineral concentration is defined as that which leads to an impairment in a function dependent on the mineral. In other cases, the convention may be to define an abnormally low mineral concentration as a level lowe…
The term mineral toxicity means a condition where the concentration in the body of any one of the minerals is abnormally high, and where there is an adverse effect on health. In general, mineral toxicity results when there is an accidental consumption of too much of any mineral, as with drinking ocean water (sodium toxicity) or with over-exposure to industrial pollutants, household chemicals, or c…
The minerals (inorganic nutrients) that are relevant to human nutrition include water, sodium, potassium, chloride, calcium, phosphate, sulfate, magnesium, iron, copper, zinc, manganese, iodine, selenium, and molybdenum. Cobalt is a required mineral for human health, but it is supplied by vitamin B12. Cobalt appears to have no other function, aside from being part of this vitamin. There is some ev…
The Minnesota Multiphasic Personality Inventory (MMPI-2; MMPI-A) is a written psychological assessment, or test, used to diagnose mental disorders. The MMPI is used to screen for personality and psychosocial disorders in adults and adolescents. It is also frequently administered as part of a neuropsychological test battery to evaluate cognitive functioning. The MMPI should be administered, scored,…
Minority health addresses the special medical and/or health needs associated with specific ethnic groups. The United States, as well as many other countries, experiences cultural diversity. This poses specific health issues that are specific to ethnic groups. Additionally, the propensity for certain diseases or illnesses is of concern in certain minority groups. These specific health issues includ…
Minoxidil is a drug available in two forms to treat different conditions. Oral minoxidil is used to treat high blood pressure and the topical solution form is used to treat hair loss and baldness. Minoxidil was the first drug approved by the FDA for the treatment of androgenetic alopecia (hair loss). Before that, minoxidil had been used as a vasodilator drug prescribed as oral tablet to treat high…
Miscarriage means loss of an embryo or fetus before the 20th week of pregnancy. Most miscarriages occur during the first 14 weeks of pregnancy. The medical term for miscarriage is spontaneous abortion. Miscarriages are very common. Approximately 20% of pregnancies (one in five) end in miscarriage. The most common cause is a genetic abnormality of the fetus. Not all women realize that they are misc…
Mitral valve insufficiency is a term used when the valve between the upper left chamber of the heart (atrium) and the lower left chamber (ventricle) doesn't close well enough to prevent back flow of blood when the ventricle contracts. Mitral valve insufficiency is also known as mitral valve regurgitation or mitral valve incompetence. Normally, blood enters the left atrium of the heart from …
Mitral valve prolapse (MVP) is a ballooning of the support structures of the mitral heart valve into the left upper collection chamber of the heart. Other names for MVP include floppy valve and Barlow's syndrome. The mitral valve is located on the left side of the heart between the top chamber (left atrium) and the bottom chamber (left ventricle). The valve opens and closes according to the…
The term stenosis means an abnormal narrowing of an opening. Mitral valve stenosis refers to a condition in the heart in which one of the valve openings has become narrow and restricts the flow of blood from the upper left chamber (left atrium) to the lower left chamber (left ventricle). In the heart, the valve that regulates the flow of blood between the left atrium and the left ventricle is call…
A mole (nevus) is a pigmented (colored) spot on the outer layer of the skin (epidermis). Moles can be round, oval, flat, or raised. They can occur singly or in clusters on any part of the body. Most moles are brown, but colors can range from pinkish flesh tones to yellow, dark blue, or black. Everyone has at least a few moles. They generally appear by the time a person is 20 and look, at first, li…
Certain African squirrels and primates carry a virus that causes monkeypox in humans. This virus is related to the smallpox virus, but it usually produces a less severe illness with fewer fatalities. However, symptoms are similar: fever, pus-filled blisters all over the body, and respiratory problems. Most monkeypox cases have been diagnosed in remote areas of central and west Africa. Contact with…
Monoamine oxidase inhibitors (MAO inhibitors) are medicines that relieve certain types of mental depression. MAO inhibitors are a type of antidepressant and are used to treat mental depression. Like other antidepressant drugs, MAO inhibitors help reduce the extreme sadness, hopelessness, and lack of interest in life that are typical in people with depression. MAO inhibitors are especially useful i…
Mood disorders are mental disorders characterized by periods of depression, sometimes alternating with periods of elevated mood. While many people go through sad or elated moods from time to time, people with mood disorders suffer from severe or prolonged mood states that disrupt their daily functioning. Among the general mood disorders classified in the fourth edition (1994) of the Diagnostic and…
Motion sickness is the uncomfortable dizziness, nausea, and vomiting that people experience when their sense of balance and equilibrium is disturbed by constant motion. Riding in a car, aboard a ship or boat, or riding on a swing all cause stimulation of the vestibular system and visual stimulation that often leads to discomfort. While motion sickness can be bothersome, it is not a serious illness…
Movement disorders are a group of diseases and syndromes affecting the ability to produce and control movement. Though it seems simple and effortless, normal movement in fact requires an astonishingly complex system of control. Disruption of any portion of this system can cause a person to produce movements that are too weak, too forceful, too uncoordinated, or too poorly controlled for the task a…
Movement therapy refers to a broad range of Eastern and Western movement approaches used to promote physical, mental, emotional, and spiritual well-being. The physical benefits of movement therapy include greater ease and range of movement, increased balance, strength and flexibility, improved muscle tone and coordination, joint resiliency, cardiovascular conditioning, enhanced athletic performanc…
Mucopolysaccharidosis (MPS) is a general term for a number of inherited diseases that are caused by the accumulation of mucopolysaccharides, resulting in problems with an individual's development. With each condition, mucopolysaccharides accumulate in the cells and tissues of the body because of a deficiency of a specific enzyme. The specific enzyme that is deficient or absent is what disti…
Mucormycosis is a rare but often fatal disease caused by certain fungi. It is sometimes called zygomycosis or phycomycosis. Mucormycosis is an opportunistic infection that typically develops in patients with weakened immune systems, diabetes, kidney failure, organ transplants, or chemotherapy. In the United States, mucormycosis is most likely to develop in the patient's nasal area or in the…
The multiple-gated acquisition (MUGA) scan is a non-invasive nuclear test that uses a radioactive isotope called technetium to evaluate the functioning of the heart's ventricles. The MUGA scan is performed to determine if the heart's left and right ventricles are functioning properly and to diagnose abnormalities in the heart wall. It can be ordered in the following patients: Pregnan…
Multiple chemical sensitivity, also known as MCS syndrome or simply MCS, is a disorder in which a person develops symptoms from exposure to chemicals in the environment. With each incidence of exposure, lower levels of the chemical will trigger a reaction and the person becomes increasingly vulnerable to reactions triggered by other chemicals. Multiple chemical sensitivity typically begins with on…
The multiple endocrine neoplasia (MEN) syndromes are three related disorders affecting the thyroid and other hormonal (endocrine) glands of the body. MEN has previously been known as familial endocrine adenomatosis. The three forms of MEN are MEN1 (Wermer's syndrome), MEN2A (Sipple syndrome), and MEN2B (previously known as MEN3). Each is an autosomal dominant genetic condition which predisp…
Multiple myeloma is a cancer in which antibodyproducing plasma cells grow in an uncontrolled and invasive (malignant) manner. Multiple myeloma, also known as plasma cell myeloma, is the second-most common cancer of the blood. It is the most common type of plasma cell neoplasm. Multiple myeloma accounts for approximately 1% of all cancers and 2% of all deaths from cancer. Multiple myeloma is a dise…
Multiple personality disorder, or MPD, is a mental disturbance classified as one of the dissociative disorders in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). It has been renamed dissociative identity disorder (DID). MPD or DID is defined as a condition in which "two or more distinct identities or personality states" alternate in controlli…
Multiple pregnancy is a pregnancy where more than one fetus develops simultaneously in the womb. Twins happen naturally about one in every 100 births. There are two types of twinning—identical and fraternal. Identical twins represent the splitting of a single fertilized zygote (union of two gametes or male/female sex cells that produce a developing fetus) into two separate individuals. They…
Multiple sclerosis (MS) is a chronic autoimmune disorder affecting movement, sensation, and bodily functions. It is caused by destruction of the myelin insulation covering nerve fibers (neurons) in the central nervous system (brain and spinal cord). MS is a nerve disorder caused by destruction of the insulating layer surrounding neurons in the brain and spinal cord. This insulation, called myelin,…
Mumps is a relatively mild, short-term viral infection of the salivary glands that usually occurs during childhood. Typically, mumps is characterized by a painful swelling of both cheek areas, although the person could have swelling on one side or no perceivable swelling at all. The salivary glands are also called the parotid glands, therefore, mumps is sometimes referred to as an inflammation of …
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. Munc…