Health Library

Macroamylasemia is the presence of an abnormal substance called macroamylase in the blood.

Macroglobulinemia of Waldenstrom is a cancer of the B lymphocytes (a type of white blood cell). It is associated with the overproduction of proteins called IgM .

Macroglossia is a disorder in which the tongue is larger than normal.

Macrosomia describes an unusually large body size. It is often used to describe an oversized fetus.

The macula lutea is the yellow oval spot at the center of the (back of the eye). It is responsible for sharp, detailed central vision (also called visual acuity).

Macular degeneration is an eye disorder that slowly destroys sharp, central vision. This makes it difficult to see fine details and read. The disease is most common in people over age 60, which is why it is often called age-related macular degeneration.

A macule is a flat, distinct, colored area of skin that is usually less than 10 millimeters wide, and does not include a change in skin texture or thickness.

Magnesium is an essential mineral for human nutrition.

Magnetic resonance angiography is an exam of the blood vessels. Unlike traditional that involves placing a tube (catheter) into the body, MRA is considered noninvasive.

may be described as feeling sad, blue, unhappy, miserable, or down in the dumps. Most of us feel this way at one time or another for short periods. True clinical depression is a mood disorder in which feelings of sadness, loss, anger, or frustration interfere with everyday life for a long period of ...

Major depression with psychotic features is a condition in which a person experiences depression along with reduced contact with reality (psychosis). This can take the form of false beliefs (delusions) or seeing or hearing something that isn’t really there (hallucinations). See also:

Malabsorption is difficulty absorbing nutrients from food.

Malaise is a generalized feeling of discomfort, illness, or lack of well-being.

Malaria is a parasitic disease that involves high fevers, shaking chills, flu-like symptoms, and anemia.

Malathion is a type of insecticide, a product used to kill or control bugs. Poisoning may occur if you swallow malathion, handle the product without gloves, or fail to wash hands soon after exposure. Significant amounts are absorbed through the skin unless proper precautions are taken. This is for ...

Male pattern baldness is the most common type of hair loss in men. It usually follows a typical pattern of receding hairline and hair thinning on the crown, and is caused by hormones and genetic predisposition.

The term “malignancy” refers to cancerous cells that have the ability to spread to other sites in the body (metastasize) or to invade and destroy tissues. Malignant cells tend to have fast, uncontrolled growth due to changes in their genetic makeup. Malignant cells that are resistant ...

Malignant hypertension is a sudden and rapid development of extremely high blood pressure. The lower (diastolic) blood pressure reading, which is normally around 80 mmHg, is often above 130 mmHg.

Malignant hyperthermia is an inherited disease that causes a rapid rise in body temperature () and severe muscle contractions when the affected person receives general . This condition is not the same as hyperthermia that is due to medical emergencies such as or infection.

Malignant otitis externa is a disorder involving inflammation and damage of the bones and cartilage at the base of the skull.

Malignant teratoma is a type of cancer made of that contain one or more of the three layers of cells found in a developing baby (embryo). These layers are callled ectoderms, mesoderms, and endoderms.

A Mallory-Weiss tear occurs in the of the lower part of the esophagus or upper part of the stomach, near where they join. The tear may bleed.

Malnutrition is the condition that occurs when your body does not get enough nutrients.

Malocclusion means the teeth are not aligned properly.

A mammogram is an picture of the breasts. It is used to find tumors and to help tell the difference between noncancerous () and cancerous (malignant) disease.

Maple syrup urine disease (MSUD) is a disorder passed down through families in which the body cannot break down certain parts of proteins. Urine in persons with this condition can smell like maple syrup.

Marfan syndrome is a disorder of connective tissue, the tissue that strengthens the body’s structures. Disorders of connective tissue affect the skeletal system, cardiovascular system, eyes, and skin.

(“pot”) intoxication is the euphoria, relaxation, and sometimes undesirable side effects that can occur when people use marijuana. Marijuana is the most commonly used illegal drug in the United States. The drug is usually smoked, but is sometimes eaten. Today, there are more than 12 ...

Marine animal stings or bites refer to poisonous bites or stings from any form of sea life, including jellyfish.

A mastectomy is surgery to remove the entire breast. It is usually done to treat .

A mastoidectomy is surgery to remove cells in the hollow, air-filled spaces in the skull behind the ear. These cells are called mastoid air cells.

Mastoiditis is an infection of the mastoid bone of the skull. The mastoid is located just behind the outside ear.

Maternal deprivation syndrome is a form of that is caused by neglect (intentional or unintentional).

Mathematics disorder is a condition in which a child’s math ability is far below normal for their age, intelligence, and education.

McArdle syndrome is the inability to break down glycogen. Glycogen is an important source of energy that is stored in muscle tissue.

McCune-Albright syndrome is a genetic disease that affects the bones and color (pigmentation) of the skin.

Measles is a very contagious (easily spread) illness caused by a virus.

Meatal stenosis is a narrowing of the opening of the urethra, the tube through which urine leaves the body.

A mechanical ventilator is a machine that assists breathing. This article discusses the use of mechanical ventilators in infants. WHY IS A MECHANICAL VENTILATOR USED? A ventilator is used to provide breathing support for ill or immature babies. Sick or babies often have breathing problems, and ...

A Meckel’s diverticulum is a pouch on the wall of the lower part of the intestine that is present at birth (congenital). The diverticulum may contain tissue that is identical to tissue of the stomach or pancreas.

Meckel’s diverticulectomy is surgery to remove an abnormal pouch on the lining of the small intestine (bowel). This pouch is called a .

Meclofenamate (Meclomen) is a nonsteroidal anti-inflammatory drug (NSAID) used to treat arthritis. Meclofenamate occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. This is for information only and not for use in the treatment or ...

Meconium aspiration syndrome is a serious condition in which a newborn breathes a mixture of and amniotic fluid into the lungs around the time of delivery.

Medial means toward the middle or center. It is the opposite of . The term is used to describe general positions of body parts. For example, the chest is medial to the arm. Your health care provider may use this term to clearly explain the relationship between things found during a physical exam.

Medial collateral ligament (MCL) injury is an injury to the ligament on the inner part of the knee. This ligament keeps your shin bone (tibia) in place. It can be a stretch, partial tear, or complete tear of the ligament.

Mediastinal tumors are growths that form in the middle of the chest area, which separates the lungs.

Mediastinitis is swelling and irritation (inflammation) of the area between the lungs (mediastinum). This area contains the heart, large blood vessels, windpipe (trachea), esophagus, thymus gland, lymph nodes, and connective tissues.

Mediastinoscopy with is a procedure in which a lighted instrument (mediastinoscope) is inserted in the space in the chest between the lungs (mediastinum), and tissue is taken (biopsy) from any unusual growth or lymph nodes.

Medullary carcinoma of the thyroid is cancer of the thyroid gland that starts in cells that release a hormone called calcitonin. Such cells are called “C” cells.

Medullary cystic kidney disease (MCKD) is a hereditary disorder in which cysts in the center of each kidney cause the kidneys to gradually lose their ability to work.

Megaloblastic anemia is a blood disorder in which there is with larger-than-normal red blood cells. Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues.

Meibomianitis is an inflammation of the meibomian glands, a group of oil-secreting (sebaceous) glands in the eyelids. These glands have tiny openings to release oils onto the surface of the cornea.

Melanoma is the most dangerous type of skin cancer. It is the leading cause of death from skin disease. It involves cells called melanocytes, which produce a skin pigment called melanin. Melanin is responsible for skin and hair color. Melanoma can also involve the colored part of the eye. For ...

Melanoma of the eye is cancer that occurs in various parts of the eye.

Melasma is a dark skin discoloration that appears on sun-exposed areas of the face.

Membranoproliferative glomerulonephritis is a kidney disorder that involves inflammation and changes in the microscopic structure of kidney cells. It leads to disrupted kidney function.

Membranous nephropathy is a kidney disorder which involves changes and inflammation of the structures inside the kidney that help filter waste and fluids. The inflammation leads to problems with kidney function.

Memory loss (amnesia) is unusual forgetfulness. It may refer to not being able to remember new events, not being able to recall one or more memories of the past, or both.

Meniere’s disease is an inner ear disorder that affects balance and hearing. See also:

Meningitis is a bacterial infection of the membranes covering the brain and spinal cord (meninges). See also:

Cryptococcal is a fungal infection of the membranes covering the brain and spinal cord (meninges). See also:

Gram-negative is an infection of the membranes covering the brain and spinal cord (meninges) from bacteria that turn pink when exposed to a special stain (Gram-negative bacteria). See also:

Haemophilus influenzae meningitis is a bacterial infection of the membranes covering the brain and spinal cord (meninges). See also:

Meningococcal meningitis is an infection that results in swelling and irritation (inflammation) of the membranes covering the brain and spinal cord. See also:

Pneumococcal meningitis is an infection that causes swelling and irritation (inflammation) of the membranes covering the brain and spinal cord (meninges). See also:

Staphylococcal is a bacterial infection of the membranes covering the brain and spinal cord (meninges). See also:

Tuberculous meningitis is an infection of the membranes covering the brain and spinal cord (meninges). See also:

Meningocele repair (also known as myelomeningocele repair) is surgery to repair birth defects of the spine and spinal membranes. Meningocele and myelomeningocele are types of .

Meningococcemia is an and potentially life-threatening infection of the bloodstream. See also:

Meniscal allograft transplantation is a type of surgery in which a new meniscus, a cartilage ring in the knee, is placed into your knee. The new meniscus is taken from a person who has died (cadaver).

Meniscus tears refer to a tear in the shock-absorbing cartilage (meniscus) of the knee.

Menkes syndrome is an in which cells in the body cannot absorb enough copper.

Menopause is the transition period in a woman’s life when her ovaries stop producing eggs, her body produces less estrogen and progesterone, and menstruation becomes less frequent, eventually stopping altogether.

Absent menstruation means no menstrual flow, or period. Absent menstruation may be: Primary — no menstruation by age 16 Secondary — menstruation begins at the appropriate age, but later stops for more than 3 cycles or 6 months Absent menstruation is called amenorrhea.

Mental retardation is a condition diagnosed before age 18 that includes below-average general intellectual function, and a lack of the skills necessary for daily living.

Menthol is used as a flavoring agent for candy and other products. This article discusses menthol poisoning from swallowing pure menthol. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local ...

Meperidine hydrochloride is a painkiller. Meperidine hydrochloride occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. This is for information only and not for use in the treatment or management of an actual poison exposure. If ...

Meprobamate is a drug used to treat anxiety. Meprobamate occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an ...

Mebromin is a germ-killing (antiseptic) liquid. Mebromin occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this substance. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an ...

Mercuric chloride is a very poisonous form of mercury. It is a type of mercury salt. There are different types of mercury poisonings. This article discusses poisoning from swallowing mercuric chloride. See also: (general overview) This is for information only and not for use in the treatment or ...

Mercuric oxide is a form of mercury. It is a type of mercury salt. There are different types of mercury poisonings. This article discusses poisoning from swallowing mercuric oxide. See also: (general overview) This is for information only and not for use in the treatment or management of an actual ...

This article discusses poisoning from mercury. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local emergency number (such as 911) or the National Poison Control Center at 1-800-222-1222.

Merthiolate is a mercury-containing substance that was once widely used as germ-killer and a preservative in many different products, including vaccines. Merthiolate poisoning occurs when large amounts of the substance are swallowed or come in contact with your skin. Poisoning may also occur if ...

Mesenteric angiography is a test used to examine the blood vessels that supply the small and large intestines. Angiography is an imaging test that uses x-rays and a special dye to see inside the arteries. Arteries are blood vessels that carry blood away from the heart.

Mesenteric artery ischemia occurs when there is a narrowing or blockage of one or more of the three mesenteric arteries, the major arteries that supply the small and large intestines.

Mesenteric venous thrombosis is a in one or more of the major veins that drain blood from the intestine.

Benign mesothelioma is a noncancerous of the lining of the lung and chest cavity, an area called the pleura. See also:

Malignant mesothelioma is an uncommon cancerous of the lining of the lung and chest cavity (pleura) or lining of the abdomen (peritoneum) that is typically due to long-term asbestos exposure.

Metabolic acidosis is a condition in which there is too much acid in the body fluids.

Metabolic neuropathies are nerve disorders that occur with diseases that disrupt the chemical processes in the body. See also: ;

Metabolic syndrome is a name for a group of risk factors that occur together and increase the risk for , , and .

Metabolism refers to all the physical and chemical processes in the body that convert or use energy, such as: Breathing Circulating blood Controlling body temperature Contracting muscles Digesting food and nutrients Eliminating waste through urine and feces Functioning of the brain and nerves

A metabolite is any substance produced during (digestion or other bodily chemical processes). In terms of medications, a metabolite usually refers to the product that remains after the drug is broken down (metabolized) by the body.

Metachromatic leukodystrophy (MLD) is a genetic disorder that affects nerves, muscles, other organs, and behavior. It slowly gets worse over time.

Metal cleaners are very strong chemical products that contain acids. This article discusses poisoning from swallowing or breathing in such products. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call ...

Metal polishes are used to clean all metals, brass, copper, or silver. This article discusses the harmful effects from swallowing metal polish. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your ...

Metastasis is the movement or spreading of cancer cells from one organ or tissue to another. Cancer cells usually spread through the bloodstream or the .

A metastatic is cancer that started in another part of the body and spread to the brain.

Metastatic cancer to the lung is cancer that starts somewhere else in the body and spreads to the lungs. See also:

Metastatic pleural tumor is a type of that has spread from another organ to the thin membrane (pleura) surrounding the lungs.

Metatarsus adductus is a foot deformity. The bones in the front half of the foot bend or turn in toward the body.

Methadone is a very strong painkiller. It is also used to treat addiction. Methadone occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. Methadone overdose can also occur if a person takes methadone with certain painkillers, such ...

Methanol is a non-drinking type of alcohol used for industrial and automotive purposes. This article discusses poisoning from an overdose of methanol. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call ...

Methanol is a nondrinking, toxic type of alcohol used for industrial and automotive purposes. It is not found in alcoholic beverages. It is sometimes called “wood alcohol.” A test can be done to measure the amount of methanol in your blood. See also:

Methapyrilene hydrochloride is an uncommon antihistamine found in cold or flu medicines. Methapyrilene hydrochloride overdose occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this medication. This is for information only and not for use in the ...

Methemoglobinemia is a blood disorder in which an abnormal amount of builds up in the blood. Hemoglobin is the oxygen-carrying molecule found in red blood cells. In some cases of methemoglobinemia, the hemoglobin is unable to carry oxygen effectively to body tissues.

Methemoglobinemia is a blood disorder in which the body cannot reuse after it is damaged. Hemoglobin is the oxygen-carrying molecule found in red blood cells. In some cases of methemoglobinemia, the hemoglobin is unable to effectively carry oxygen to body tissues. Acquired methemoglobinemia ...

Methyl salicylate is a wintergreen-scented chemical found in many over-the-counter products, including muscle ache creams. Methyl salicylate occurs when someone accidentally or intentionally takes more than the normal or recommended amount of a product containing this substance. This is for ...

The methylene blue test is used to determine the type of the blood disorder, .

Methylmalonic acid is a substance produced when proteins (amino acids) in the body break down. A test can be done to measure the amount of methylmalonic acid in your blood.

Methylmalonic acidemia is a disorder, passed down through families, in which the body cannot break down certain proteins and fats. The result is a build up of a substance called methylmalonic acid in the blood. It is considered an inborn error of metabolism.

Methylmercury poisoning is brain and nervous system damage from the chemical methylmercury.

A metopic ridge is an abnormal shape of the skull. The ridge can be seen on the forehead.

An MIBG scintiscan is an imaging test that uses a radioactive substance (called a tracer) and a special scanner to find or confirm the presence of and neuroblastoma, which are tumors of specific types of nervous tissue. See also:

This test looks for a protein called albumin in a urine sample. See also:

Microcephaly is a condition in which a person’s head is significantly smaller than normal for their age and sex, based on standardized charts. Head size is measured as the distance around the top of the head.

Micrognathia is a term that describes an abnormally small lower jaw.

A migraine is a common type of headache that may occur with symptoms such as nausea, vomiting, or sensitivity to light. In many people, a throbbing pain is felt only on one side of the head. Some people who get migraines have warning symptoms, called an aura, before the actual headache begins. An ...

Mildew removers are common household cleaners. Swallowing, breathing in the product, or spraying it in the eyes can be potentially dangerous. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your ...

Milia are tiny white bumps or small cysts on the skin.

Milk-alkali syndrome is an acquired condition in which there are high levels of calcium () and a shift in the body’s acid/base balance towards alkaline (metabolic ).

Millipedes are worm-like bugs called arthropods. Certain types of millipedes release a harmful substance (toxin) if they are threatened or if you handle them roughly. Millipedes can squirt toxin several inches. This is for information only and not for use in the treatment or management of an ...

Mineral metabolism disorders are abnormal levels of minerals — either too much or too little — in the blood. Minerals are very important for the human body. They have various roles in metabolism and body functions. They are essential for the proper function of cells, tissues, and ...

Mineral oil is a liquid oil produced from petroleum. Mineral oil overdose occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this substance. This is for information only and not for use in the treatment or management of an actual poison exposure. ...

This article discusses the harmful effects from swallowing or breathing in mineral spirits. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local emergency number (such as 911) or the National ...

Minimal change disease is a kidney disorder that can lead to , although the nephrons of the kidney look normal under a regular microscope.

A miscarriage is the spontaneous loss of a fetus before the 20th week of pregnancy. (Pregnancy losses after the 20th week are called preterm deliveries.) A miscarriage may also be called a “spontaneous abortion.” This refers to naturally occurring events, not medical abortions or . ...

A threatened miscarriage is a condition that suggests a might take place before the 20th week of pregnancy.

Mistletoe is an evergreen plant with white berries. Mistletoe poisoning occurs when someone eats any part of this plant. Poisoning can also occur if you drink tea created from the plant or its berries. This is for information only and not for use in the treatment or management of an actual poison ...

Acute mitral regurgitation is a disorder in which the heart’s mitral valve suddenly does not close properly, causing blood to flow backward (leak) into the upper heart chamber when the left lower heart chamber contracts. See also:

Chronic mitral regurgitation is a long-term disorder in which the heart’s mitral valve does not close properly, causing blood to flow backward (leak) into the upper heart chamber when the left lower heart chamber contracts. The condition is progressive, which means it gradually gets worse. ...

Mitral stenosis is a heart valve disorder that involves the mitral valve. This valve separates the upper and lower chambers on the left side of the heart. Stenosis refers to a condition in which the valve does not open fully, restricting blood flow.

Mitral valve prolapse is a heart problem in which the valve that separates the upper and lower chambers of the left side of the heart does not close properly.

Mitral valve surgery is surgery to either repair or replace the mitral valve in your heart. Blood that comes from the lungs enters the left atrium of the heart and crosses into the left ventricle. The mitral valve between these two chambers makes sure that the blood keeps moving forward. when the ...

Mitral valve surgery is surgery that can either repair or replace the mitral valve in your heart. Blood that flows between different chambers of your heart must flow through a valve. One such valve is called the mitral valve. It opens up enough so blood can flow from one chamber of your heart ...

Mittelschmerz is one-sided, lower abdominal pain that occurs in women at or around the time of an egg is released from the ovaries (ovulation).

Mixed tension migraine is a headache with features of both tension and migraine headaches. See also:

The MMR vaccine is a “3-in-1” vaccine that protects against , , and — all of which are potentially serious diseases of childhood.

Molluscum contagiosum is a viral skin infection that causes raised, pearl-like or on the skin.

Mongolian spots are flat, blue, or blue-gray skin markings that commonly appear at birth or shortly thereafter. See also:

Mononeuritis multiplex is a nervous system disorder that involves damage to at least two separate nerve areas.

Mononeuropathy is damage to a single nerve or nerve group, which results in , sensation, or other function of that nerve.

Mononucleosis is a viral infection causing fever, sore throat, and swollen lymph glands, especially in the neck. See also: (acute CMV infection)

The mononucleosis spot test looks for two in the blood that indicate infection with the Epstein-Barr virus (EBV).

Morning sickness is that can actually occur at any time of the day during pregnancy. See also:

Moro reflex is type of involuntary response that is present at birth. It normally disappears after 3 or 4 months. See also:

Morphine is a very strong painkiller. Morphine overdose occurs when a person intentionally or accidentally takes too much of the medicine. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local ...

Morquio syndrome is an inherited disease of metabolism in which the body is missing or doesn’t have enough of a substance needed to break down long chains of sugar molecules called glycosaminoglycans (formerly called mucopolysaccharides). The syndrome belongs to a group of diseases called ...

Morton’s neuroma is a thickening of nerve tissue between the toes. It commonly affects the nerve that travels between the third and fourth toes. See also:

Mosaicism is a condition in which cells within the same person have a different genetic makeup. This condition can affect any type of cell, including: Blood cells Egg and sperm cells (gametes) Skin cells

Different types of sores can appear anywhere in the mouth, including the inner cheeks, gums, tongue, lips, or palate.

Mouth are sores or open lesions in the mouth. See also:

Mouthwash occurs when someone accidentally or intentionally takes more than the normal or recommended amount of this substance. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local emergency ...

Uncontrollable movements are slow, twisting, continuous, and involuntary movements of the arms, legs, face, neck, or other parts of the body. See also:

Uncontrolled or slow movement is defined as a problem with muscle tone, usually in large muscle groups, that leads to slow involuntary contractions of the head, limbs, trunk, or neck. See also: Tremor

Uncoordinated movement is muscle control problem or an inability to finely coordinate movements, which results in a jerky, unsteady, to-and-fro motion of the middle of the body (trunk) and (walking style). The condition is called ataxia.

Jerky body movements is a condition in which uncontrolled, purposeless, rapid motions interrupt normal movement or posture.

Magnetic resonance imaging (MRI) is a noninvasive method to take pictures of the body. Unlike and computed tomographic () scans, which use radiation, MRI uses powerful magnets and radio waves. Signals from the magnetic field bounce off your body and are sent to a computer, where they are turned ...

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial infection that is highly resistant to some antibiotics.

Mucopolysaccharides are long chains of sugar molecules that are found throughout the body, often in mucus and in fluid around the joints. They are more commonly called glycosaminoglycans.

Mucormycosis is a fungal infection of the sinuses, brain, or lungs that occurs mostly in people with weakened immune systems.

Mucosa is moist tissue that lines certain parts of the inside of your body, including your nose, mouth, lungs, and the urinary and digestive tracts. Glands in the mucosa release a thick fluid called mucus.

A mucous is a painless, thin sac on the inner surface of the lips. It contains clear fluid.

Multi-infarct dementia (MID) is a form of dementia caused by a series of small . Dementia is a loss of brain function that occurs with certain diseases. It affects memory, thinking, language, judgment, and behavior.

Multifocal atrial tachycardia is a that occurs when too many signals (electrical impulses) are sent from the upper heart to the lower heart.

Multiple endocrine neoplasia (MEN) type I is an inherited disorder in which one or more of the endocrine glands are overactive or form a tumor. Endocrine glands most commonly involved include: Pancreas Parathyroid Pituitary

Multiple endocrine neoplasia, type II (MEN II) is an inherited disorder in which one or more of the endocrine glands are overactive or form a tumor. Endocrine glands most commonly involved include: Adrenal (about half the time) Parathyroid (20% of the time) Thyroid (almost all of the time) See also:

Multiple lentigines syndrome is an inherited disorder identified by an increased number of lentigines (freckle-like spots).

Multiple myeloma is of the plasma cells in bone marrow.

Multiple sclerosis is an that affects the brain and spinal cord ().

Multiple system atrophy (MSA) is a rare condition that causes symptoms similar to . However, patients with MSA have more widespread damage to the part of the nervous system that controls important functions such as heart rate, blood pressure, and sweating.

Multiple vitamin occurs when someone accidentally or intentionally takes more than the normal or recommended amount of multivitamin supplements. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your ...

Mumps is a contagious disease that leads to painful swelling of the salivary glands. The salivary glands produce saliva, a liquid that moistens food and helps you chew and swallow. See also:

Munchausen syndrome by proxy is a form of in which a parent induces real or apparent symptoms of a disease in a child.

Muscle aches and pains are common and can involve more than one muscle. Muscle pain also can involve ligaments, tendons, and fascia, the soft tissues that connect muscles, bones, and organs. See also:

Muscle atrophy is the wasting or loss of tissue.

A muscle biopsy is the removal of a small piece of muscle tissue for examination.

Muscle cramps are involuntary and often painful movements (contractions) of the muscles. The most commonly involved muscle groups are: Back of the lower leg/calf (gastrocnemius) Back of the thigh (hamstrings) Front of the thigh (quadriceps) Cramps in the feet, hands, arms, abdomen, and along the ...

Muscle function loss is when a muscle doesn’t work or move normally. The medical term for complete loss of muscle function is paralysis.

Muscle twitches are fine movements of a small area of muscle.

Muscular dystrophy is a group of inherited disorders that involve and loss of muscle tissue, which get worse over time.

Myasthenia gravis is a neuromuscular disorder. Neuromuscular disorders involve the muscles and the nerves that control them.

Mycobacterial culture is a test to look for tuberculosis or a related organism in the body. It can be done on tissue taken from the bone marrow, liver, or lungs. See also: Atypical mycobacterial infection

Mycoplasma pneumonia is an infection of the lungs from the bacteria Mycoplasma pneumoniae (M. pneumoniae). See also:

Myelin is an insulating layer that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. The purpose of the myelin sheath is to allow rapid and efficient transmission of impulses along the nerve cells. If the myelin is damaged, the impulses ...

Myelofibrosis is a disorder of the bone marrow, in which the marrow is replaced by scar (fibrous) tissue.

Myelomeningocele is a birth defect in which the backbone and spinal canal do not close before birth. The condition is a type of spina bifida.

Myocardial biopsy is the removal of a small piece of heart muscle for examination.

Myocardial contusion is a “bruise” of the heart .

Myocarditis is inflammation of the heart muscle. See also:

Pediatric myocarditis is inflammation and weakness of the heart muscle in an infant or young child.

Serum myoglobin is a test that measures the amount of myoglobin in the blood. Myoglobin is a protein in heart and skeletal muscles. When you exercise, your muscles use up any available oxygen. Myoglobin has oxygen attached to it, which provides extra oxygen for the muscle to maintain a high level ...

Urine myoglobin is a test to detect the presence of myoglobin in a sample of urine. Myoglobin is a protein in heart and skeletal muscles. When a muscle is exercised, it uses up available oxygen. Myoglobin has oxygen attached to it, which provides extra oxygen for the muscle to maintain a high ...

Myopathic changes are weakness or biopsy results that suggest a muscle disorder, such as .

Myositis is an inflammation or swelling of the muscles, often caused by injury, infection, or an . See also:

Myotonia congenita is an inherited condition that affects muscle relaxation. It is congenital, meaning that it is present from birth.

Myristica oil is a clear liquid that smells like the spice nutmeg. Myristica oil poisoning occurs when someone swallows this substance. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local ...