uterus (an invasive mole). A molar preg-
nancy that becomes cancerous is called
a choriocarcinoma.
If the dead embryo and placenta are
not expelled from the uterus after a mis-
carriage, the dead tissue is called a
carneous mole.
moleA type of pigmented naevus. (See
also molar pregnancy.)
moleculeThe smallest complete unit of
a substance that can exist independ-
ently and still retain the characteristic
properties of that substance. Almost all
molecules consist of 2 or more atoms
that are bonded together. Molecules
that consist of only one atom are known
as monatomic molecules.
molluscum contagiosumA harmless
viral infection characterized by shiny,
pearly white papules (tiny lumps) on
the skin surface. Each papule has a cen-
tral depression, and produces a cheesy
fluid when it is squeezed. A crust forms
before healing occurs.
The papules often appear on the geni-
tals, the inside of the thighs, or the face.
Children are more commonly affected
than adults. The infection is transmit-
ted by direct skin contact or during
sexual intercourse; it usually clears up
within a few months, but may last for
up to 18 months.Mongolian blue spotA blue-black
pigmented spot found on the lower
back and buttocks at birth. The spots
are a type of naevusand are caused by a
concentration of melanocytes (pigment-
producing cells). Mongolian blue spots
are commonly found in black or Asian
children, and they usually disappear by
the age of 3–4 years.MongolismAn outdated name for
Down’s syndrome.
moniliasisSee candidiasis.
monitorTo maintain a constant watch
on the condition of a patient. Also, any
device used to carry out monitoring.
monoamine oxidase inhibitorsAlso
known as MAOIs, one of the 3 main
types of antidepressant drug. They work
by preventing the breakdown of certain
neurotransmittersby the enzymemono-
amine oxidase. The increased levels of
neurotransmitters that result are asso-
ciated with improved mood. Common
drugs include phenelzineand isocarbox-
azid. All MAOIs interact with certain
other drugs and foods such as cheese
and red wine; but moclobemideis known
as a reversible MAOI, which makes the
adverse reactions less likely to occur.
monoarthritisInflammation of a single
joint, causing pain and stiffness. Com-
mon causes of monoarthritis include
osteoarthritis, gout, and infection.
monoclonal antibodySee antibody,
monoclonal.
monocyteOne of the main types of
white blood cell. Monocytes are phago-
cytes, and play an important role in the
immune system.
mononucleosis, infectiousAn acute
viral infection characterized by a high
temperature, sore throat, and swollen
lymph nodes, particularly in the neck.
Commonly called glandular fever, it is
caused by the Epstein–Barr virusand
is most common during adolescence or
early adulthood. One common mode of
transmission is thought to be kissing.
In the body, the virus multiplies in the
lymphocytes(also called mononuclear
cells), which develop an atypical appear-
ance. The first symptoms are a fever and
headache, followed by swollen lymph
nodes and a severe sore throat. Rarely,
enlargement of the tonsils may obstruct
breathing. Mild inflammation of the
liver may occur, leading to jaundice.
Diagnosis is often made from the symp-
toms and a blood test. Recovery usually
takes 4–6 weeks, with rest the only
treatment needed. In rare cases, cortico-
steroid drugs are given to reduce severe
inflammation, particularly if breathing
is obstructed. For 2–3 months afterMOLE MONONUCLEOSIS, INFECTIOUSM
MOLLUSCUM CONTAGIOSUM
Pearly white papule