Dictionary

multiple gestation A pregnancy in which two or more fetuses are present in the womb.

multiple myeloma A bone marrow cancer that involves a type of white blood cell called a plasma (or myeloma) cell. The tumor cells in myeloma can form a single collection (plasmacytoma) or many tumors (multiple myeloma). Plasma cells are normally part of the immune system; they make antibodies. Because myeloma patients have an excess of…

multiple personality disorder See dissociative disorder.

multiple sclerosis A disease that is characterized by loss of myelin (demyelinization). Abbreviated MS. Myelin, the coating of nerve fibers, is composed of lipids (fats) and protein. It serves as insulation and permits efficient nerve fiber conduction. In MS, demyelinization usually affects white matter in the brain, but sometimes it extends into the gray matter….

mumps An acute viral illness that is caused by a paramyxovirus and that usually presents with inflammation of the salivary glands, particularly the parotid glands. A child with mumps often looks like a chipmunk with a full mouth due to the swelling of the salivary glands near the ears. Mumps can also cause inflammation of…

mumps immunization A vaccination for mumps. Mumps immunization may be given individually, or together with the measles and rubella vaccines, in the MMR immunization, or with the MMR vaccine modified to include a vaccine against varicella (MMRV). See also MMR; MMRV.

mumps in pregnancy Mumps contracted in pregnancy, which can cause early miscarriage or birth defects. The most common birth defect associated with mumps is congenital deafness. Mumps vaccination is not recommended during or shortly before pregnancy because it is a live attenuated vaccine, so carries a risk of causing mumps infection.

Munchhausen by proxy A form of Munchhausen syndrome in which a parent feigns illness in a child. In some cases the parent is simply overanxious or poorly informed. In others, a misdirected desire for attention or psychiatric illness is the cause. In a very few cases, the parent actually causes the child’s illness, as by…

Munchhausen syndrome Recurrent feigning of catastrophic illnesses. Some patients with Munchhausen syndrome actually cause their own illness, as by secretly drinking or injecting substances. Munchhausen syndrome may be caused by a misdirected desire for attention, although in some cases it arises in actual psychiatric illness. It is named for the fictitious Baron Munchhausen, who told…

muscle The tissue of the body that functions primarily as a source of power. There are three types of muscle in the body: Muscle that is responsible for moving extremities and external areas of the body is called skeletal muscle, heart muscle is called cardiac muscle, and muscle in the walls of arteries and the…

muscle, abductor Any muscle that pushes away from the midline of the body. For example, the abductor muscles of the arms allow the arms to be raised from one’s sides. Abductor muscles are opposed by adductor muscles. To keep these similar-sounding terms straight, medical students learn to speak of “A B ductors” versus “A D…

muscle, adductor Any muscle that pulls inward toward the midline of the body. For example, the adductor muscles of the leg serve to pull the legs together. Adductor muscles are opposed by abductor muscles. To keep these similar-sounding terms straight, medical students learn to speak of “A D ductors” versus “A B ductors.”