Webster's New World Medical Dictionary

hyperexplexia
A rare genetic disorder inherited
in an autosomal dominant manner in which babies
have an exaggerated startle reflex. Symptoms at
birth may include muscle stiffness (hypertonia), an
exaggerated response to being startled, and strong
brain stem reflexes (especially head-retraction
reflex). The startle reflex is sometimes accompa-
nied by sudden stiffness (acute generalized hyperto-
nia), which can cause the affected person to fall to
the ground like a log. Treatment is via medications.
Also known as exaggerated startle disease, hyperek-
plexia, Kok disease, startle disease, and stiff baby
syndrome.
hyperglycemia
Elevated blood glucose (sugar).
Hyperglycemia is often found in diabetes mellitus.
See also 
diabetes mellitus.
hyperhidrosis
A condition characterized by
extreme and excessive sweating. Primary hyper-
hidrosis affects the hands, feet, and armpits and
often has no identifiable cause. If the sweating
occurs as a result of another medical condition, it is
called secondary hyperhidrosis. In secondary
hyperhidrosis, the sweating may be all over the body
or may be localized to one area. A number of med-
ical conditions can cause secondary hyperhidrosis.
hyperkalemia
Elevated potassium in the blood.
Hyperkalemia can be caused by taking excessive
amounts of potassium, by medications, tissue
trauma, and by diseases such as kidney failure.
Hyperkalemia may not produce any symptoms, but
severe hyperkalemia can lead to potentially fatal
arrythmias of the heart.
hyperkeratosis
Thickening of the outer layer of
skin, which is composed of the protein keratin.
Causes include normal wear and tear, inflammation
of the skin, or genetic conditions.
hyperlipidemia
Elevated lipid (fat) levels in the
blood. Hyperlipidemia can be inherited and
increases the risk of disease of the blood vessels
leading to stroke and heart disease.
hypermagnesemia
Excess magnesium in the
blood. Kidney disease is one of the main causes of
hypermagnesemia. Persons with impaired kidney
function should be especially careful about their
magnesium intake because they can accumulate
magnesium, which is dangerous and sometimes
fatal.