Webster's New World Medical Dictionary

acute HIV infection
See 
HIV infection, acute.
acute idiopathic polyneuritis
See 
Guillain-
Barre syndrome.
acute illness
A disease with an abrupt onset and,
usually, a short course.
acute leukemia
Cancer of the blood cells that
characteristically comes on suddenly and, if not
treated, progresses quickly. In acute leukemia, the
leukemic cells are not able to mature properly.
acute membranous gingivitis
A progressive
and painful infection of the mouth and throat due to
the spread of infection from the gums. Symptoms
include ulceration, swelling, and sloughing off of
dead tissue from the mouth and throat. Certain
germs (including fusiform bacteria and spiro-
chetes) have been thought to be involved, but the
actual cause is not yet known. Like most other
poorly understood diseases, acute membranous
gingivitis goes by many other names, including
acute necrotizing ulcerative gingivitis, fusospirillary
gingivitis, fusospirillosis, fusospirochetal gingivitis,
necrotizing gingivitis, phagedenic gingivitis, trench
mouth, ulcerative gingivitis, ulcerative stomatitis,
Vincent angina, Vincent gingivitis, Vincent infection,
and Vincent stomatitis.
acute mountain sickness
The physical effect of
being in a high-altitude environment. Abbreviated
AMS, it is common at altitudes above 2,440
meters (approximately 8,000 feet). Three-fourths of
people have mild symptoms of AMS at altitudes over
3,048 meters (approximately 10,000 feet).
Occurrence depends on the altitude, rate of ascent,
and individual susceptibility. Symptoms begin 12 to
24 hours after arrival at a new altitude and include
headache, dizziness, fatigue, shortness of breath,
loss of appetite, nausea, disturbed sleep, and gen-
eral malaise. These symptoms tend to worsen at
night, when the respiratory drive is decreased.
Symptoms should subside within 2 to 4 days,
and can be treated by using pain medications such
as aspirin. Acetazolamide (brand name: Diamox)
can also be used to minimize symptoms and may be
taken as a preventive measure. Moderate AMS has
the same symptoms as AMS, but the headaches can-
not be relieved with medication, and both breathing
and coordinated movements become difficult. The
only remedies are advanced medications and
descent to lower altitudes. Severe AMS causes great
shortness of breath at rest, inability to walk,
decreased mental status, and fluid buildup in the
lungs. Severe AMS requires immediate descent to
lower altitudes: 610 to 1,220 meters (approxi-
mately 2,000 to 4,000 feet). See also 
acclimati-
zation to altitude.