Webster's New World Medical Dictionary

humorism
See 
humoralism.
Hunter syndrome
A genetic metabolic disorder
that arises from deficiency of the enzyme iduronate
sulfatase, resulting in tissue deposits of molecules
called mucopolysaccharides. Hunter syndrome is
inherited as an X-linked recessive trait. The charac-
teristic features of Hunter syndrome include
dwarfism, bone deformities, a thickened, coarse
face, hepatosplenomegaly (enlargement of the liver
and spleen) from mucopolysaccharide deposits,
cardiovascular disorders from mucopolysaccharide
deposits, and deafness. There are two forms of
Hunter syndrome: a severe form that causes pro-
gressive mental retardation, physical disability, and
death before age 20 in most cases; and a mild form
in which patients survive to adulthood, are able to
reproduce, and have intellect that is impaired mini-
mally, if at all. The gene for the enzyme iduronate
sulfatase (deficient in Hunter’s syndrome) is on the
X chromosome. Also known as mucopolysacchari-
dosis II.
Huntington’s chorea
See 
Huntington’s
disease.
Huntington’s disease
A genetic degenerative
disorder of the brain cells characterized by pro-
gressive mental and physical deterioration that
leads to death. Abbreviated HD. Although HD is usu-
ally an adult-onset disorder, it can affect children as
well. The average survival time is 15 to 18 years
after the onset of symptoms. Mood disturbance is
usually the first symptom seen, with bipolar disor-
der–like mood swings that may include mania,
depression, extreme irritability or angry outbursts,
and psychosis. Other symptoms include chorea
(restless, wiggling, turning movements), muscle
stiffness and slowness of movement, and difficulties
with memory and other cognitive processes. HD is
inherited in an autosomal dominant manner. The
HD gene is on chromosome 4. Diagnosis is made
via molecular genetic testing. At this time there is no
cure for HD, although medication may be used to
control symptoms of the illness, such as mood
swings and chorea. See also 
chorea.
Hurler syndrome
An inherited error of metabo-
lism characterized by deficiency of the enzyme
alpha-L-iduronidase, which normally breaks down
molecules called mucopolysaccharides. Without the
activity of this enzyme, mucopolysaccharides accu-
mulate abnormally in the tissues of the body. There
are two clinical subtypes of disease due to defi-
ciency of alpha-L-iduronidase: Hurler syndrome
and Scheie syndrome. Hurler syndrome patients
have progressive mental degeneration, a broad
forehead with heavy eyebrows, enlarged and
deformed skull, small stature, corneal opacities,
hepatosplenomegaly (enlargement of the liver and
spleen), valvular heart defects, thick skin, joint con-
tractures, and hernias. Hurler syndrome is inherited
in an autosomal recessive manner. The gene that
codes for alpha-L-iduronidase is on chromosome 4.
Enzyme replacement therapy helps the body make
alpha-L-iduronidase and can alleviate many of the
symptoms, but enzyme replacement therapy has not
been shown to affect the mental damage. Bone mar-
row transplantation may slow the progression of
Hurler syndrome and may prevent mental retarda-
tion if done at an early age. Also known as
mucopolysaccharidosis type I.