mutismRefusal or inability to speak.
Mutism may occur as a symptom of
profound congenital deafness, severe
manic–depressive illness, catatonic schiz-
ophrenia, or a rare form of conversion
disorder. The term may also apply to a
religious vow of silence.
Elective mutism is a rare childhood
disorder (usually starting before age 5),
in which the child can speak properly
but refuses to do so most of the time.
Akinetic mutism describes a state of
passivity caused by some brain tumours
or by hydrocephalus. People with akin-
etic mutism are incontinent, require
feeding, and respond at most with a
whispered "yes" or "no".
myalgiaMedical term for musclepain.
myalgic encephalomyelitisAlso known
as ME (see chronic fatigue syndrome).
myasthenia gravisA rare disorder in
which the muscles become weak and
tire easily. The muscles of the eyes,
face, throat, and limbs are most com-
monly affected.
Myasthenia gravis is an autoimmune
disorder.In many cases, abnormalities
in the thymus gland are present, and in
some cases a thymomais found. Women
are affected more often than men.
The disease is extremely variable in its
effects. In most cases, it causes droop-
ing eyelids, double vision, a blank facial
expression, and a weak, hoarse, nasal
voice that is hesitant and becomes slur-
red during extended conversation. The
arm and leg muscles may also be affec-
ted. In severe cases, the respiratory
muscles may become weakened, caus-
ing breathing difficulty.
Diagnosis of the condition is often
made by injecting the drug edrophonium
into a vein. This temporarily restores
power to the weak muscles. Blood tests
and EMGare also sometimes used. CT
scanningor MRImay also be performed
to look for a thymoma.
Treatment with drugs that facilitate
transmission of nerve impulses often
restores the patient’s condition to near
normal. In some cases, the condition
often improves, and is sometimes cured
by thymectomy (removal of the thymus
gland). Regular exchanges of the pati-
ent’s plasmafor fresh plasma may becarried out in severe cases. Cortico-
steroid drugsmay be given. In a minority
of patients, paralysisof the throat and
respiratory muscles may lead to death.
mycetomaAn uncommon tropical infec-
tion affecting skin and bone and caused
by fungior by actinomycetes (bacteria
that form long chain-like colonies). It
usually occurs on one limb, producing a
hard swelling and a discharge of pus.
Infections caused by actinomycetes are
treated with antibiotic drugs. Surgical
removal of diseased tissue may be nec-
essary for a fungal infection.
mycologyThe study offungi.
mycoplasmaAny of a group of bacteria
that are the smallest type capable of
free existence. Mycoplasmas are about
the same size as virusesbut, unlike
viruses, they are capable of reproducing
outside living cells. One species,
MYCOPLASMA PNEUMONIAE, causes pri-
mary atypical pneumonia.
mycosisAny disease caused by a fun-
gus. (See fungi; fungal infections.)
mycosis fungoidesA rare type of lym-
phomathat primarily affects the skin of
the buttocks, back, or shoulders. The
cause of mycosis fungoides is unknown.
In its mildest form, it produces a non-
itchy, red, scaly rash, which may spread
slowly or remain unaltered for many
years. In more severe forms, thickened
patches of skin, ulcers, and enlarged
lymph nodesmay develop.
The diagnosis is confirmed with a skin
biopsy. Treatment may include PUVA,
radiotherapy, nitrogen mustard, anti-
cancer drugs, and corticosteroid drugs.
mydriasisDilation (widening) of the
pupil of the eye. It occurs in the dark, if
a person is emotionally aroused, after
the use of certain eye-drops (such as
those containing atropine), and after
consumption of alcohol.
mydriatic drugsA group of drugs
used to treat uveitisand to dilate the
pupil during examination of the inside
of the eye and for surgery. Mydriatics
work by relaxing the circular muscles of
the iris, causing the pupil to dilate.
Common mydriatic drugs include tropi-
camide, cyclopentolate, homatropine,
and phenylephrine. (See also cyclople-
gia; miotic drugs.)MUTISM MYDRIATIC DRUGSM