CD-ROM Today 1996 January/CD-ROM Today 1996 January.iso/dp/0383/03831.txt

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$Unique_ID{BRK03831}
$Pretitle{}
$Title{Hunter Syndrome}
$Subject{Hunter Syndrome Mucopolysaccharidosis Type II MPS II MPS Disorder MPS
IIA MPS IIB}
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Copyright (C) 1986, 1987, 1988, 1990 National Organization for Rare
Disorders, Inc.

282:
Hunter Syndrome

** IMPORTANT **
It is possible the main title of the article (Hunter Syndrome) is not the
name you expected.  Please check the SYNONYMS listing to find the alternate
names and disorder subdivisions covered by this article.

Synonyms

     Mucopolysaccharidosis Type II
     MPS II
     MPS Disorder

DISORDER SUBDIVISIONS

     MPS IIA
     MPS IIB

General Discussion

** REMINDER **
The information contained in the Rare Disease Database is provided for
educational purposes only.  It should not be used for diagnostic or treatment
purposes.  If you wish to obtain more information about this disorder, please
contact your personal physician and/or the agencies listed in the "Resources"
section of this report.


Mucopolysaccharidoses (MPS Disorders) are a group of rare genetic
disorders caused by the deficiency of one of ten specific lysosomal enzymes
resulting in an inability to metabolize complex carbohydrates
(mucopolysaccharides) into simpler molecules.  The accumulation of these
large, undegraded mucopolysaccharides in the cells of the body causes a
number of physical symptoms and abnormalities.

The most prevalent form of MPS Type II is called Hunter Syndrome.  The
disorder can be manifested in a mild or a severe form.

Symptoms

Two types of Hunter syndrome (MPS II) have been recognized, mild and severe,
both with the same enzymatic deficiency, iduronate sulfatase.  The severe
form of Hunter syndrome has features similar to Hurler syndrome except for
the lack of corneal clouding and slower progression of physical involvement
and mental retardation.

In the severe form of this disorder, physical and mental development reach a
peak at 2-4 years of age with subsequent deterioration.  Recurrent urinary and
upper respiratory infections, a chronic runny nose, liver enlargement, joint
stiffness and growth failure commonly occur with the severe from of Hunter
syndrome.  Coarsening of the facial features with thickening of the nostrils,
lips and tongue usually occur between 2 and 4 years of age.  Hydrocephalus is
commonly found in this form of Hunter syndrome after 4 years of age.  (For
more information, choose "hydrocephalus" as your search term in the Rare
Disease Database.)  Thick skin, short neck, widely spaced teeth, and hearing
loss of varying degree are also commonly present.  Nodular skin lesions on the
arm or the posterior chest wall, extra-high arched feet (pes cavus) and
diarrhea also may occur.

In the mild form of Hunter syndrome, mental function is usually normal
and physical deterioration is greatly reduced compared to the severe form.
Complications of the mild form of the disorder may include heart, coronary
and valvular disease, hearing impairment, reduced circulation in the hands
due to compression of veins in the wrist (carpal tunnel syndrome), and joint
stiffness which can result in loss of hand function.

Causes

Hunter Syndrome is an x-linked recessive hereditary disorder, in which a
deficiency in the enzyme odirpmate sulfatase causes the physical and mental
deterioration.  (Human traits including the classic genetic diseases, are the
product of the interaction of two genes for that condition, one received from
the father and one from the mother.  X-linked recessive disorders are
conditions which are coded on the X chromosome.  Females have two X
chromosomes, but males have one X chromosome and one Y chromosome.  Therefore
in females, disease traits on the X chromosome can be masked by the normal
gene on the other X chromosome.  Since males have only one X chromosome, if
they inherit a gene for a disease present on the X, it will be expressed.
Men with X-linked disorders transmit the gene to all their daughters, who are
carriers, but never to their sons.  Women who are carriers of an X-linked
disorder have a fifty percent risk of transmitting the carrier condition to
their daughters, and a fifty percent risk of transmitting the disease to
their sons.)

Affected Population

Hunter Syndrome affects only males, with symptoms becoming apparent at
approximately 2-4 years of age.  The disorder occurs in 1 out of 100,000 live
births.

Related Disorders

There are many types of Mucopolysaccharidoses.  (For more information, choose
"MPS Disorder" as your search term in the Rare Disease Database.)

DiFerrante syndrome (Mucopolysaccharidosis VIII) is a disorder described
in a single patient with clinical and biochemical features of Morquio and
Sanfilippo syndromes.  The disorder had been reported to be due to a
deficiency of glucosamine-6-sulfate sulfatase.  Subsequently, this disorder
was called MPS VIII (DiFerrante syndrome).  Dr. DiFerrante later found that
the enzyme was normal in his patient, and the disorder had been misdiagnosed.
Therefore, DiFerrante syndrome is not a valid medical disorder.

The Mucolipidoses are a family of similar disorders, producing symptoms
very much like those of the Mucopolysaccharidoses.

I-cell disease, or Mucolipidosis Type II, resembles Hurler syndrome and
the two disorders are very difficult to distinguish.  I-cell disease has
similar physical and mental deterioration as MPS I, but usually occurs
earlier and is more severe.  I-cell disease is characterized by diffused
deficiency of lysosomal enzymes within the cell and is not associated with
excretion of mucopolysaccharides in the urine.  (For more information, choose
"I-Cell Disease" as your search term in the Rare Disease Database.)

Pseudo-Hurler Polydystrophy (Mucolipidosis III) is also transmitted by
autosomal inheritance, but it is characterized by a deficiency of multiple
lysosomal enzymes needed to break down mucopolysaccharides.  ML III affects
males more often than females, and can be identified by such symptoms as
claw-like hands, somewhat coarse facial features, dwarfism and pain in the
hands.  Intelligence tends to be normal in most patients, but mild mental
retardation is possible.

Ganglioside Sialidase Deficiency (Mucolipidosis IV) is a disorder of unknown
cause characterized by early clouding of the cornea, mild to moderate mental
retardation and enlargement of spleen and liver.

(For more information on the Mucolipidoses, choose "ML Disorder" as your
search term in the Rare Disease Database.)

Therapies:  Standard

Treatment of Hunter Syndrome is symptomatic and supportive.  Hernias and
joint contractures may be corrected by surgery.  Surgical implantation of a
ventricular shunt may be used to treat possible hydrocephalus.  Hearing
devices may be prescribed to treat hearing loss.  Physical therapy, medical
and genetic counseling services may be helpful to patients and families.
Prenatal diagnosis is now possible for this disorder.

Therapies:  Investigational

Since prenatal diagnosis is now possible through amniocentesis and sampling
of a tissue layer in the embryo (chorionic villus sampling), new treatments
aimed at checking early development of Hunter Syndrome are now under study.
One method involves replacing defective enzymes via enzyme replacement
therapy and/or bone marrow transplants.  Scientific study of gene replacement
in animal models raises the hope that gene replacement may someday be made
available to people with genetic disorders such as Hunter Syndrome.

The Mayo Clinic is investigating the use of Alpha Interferon as a
treatment for Hunter Syndrome.  For more information, physicians can contact:

     Morie A. Gertz, M.D.
     Dept. of Hematology & Internal Medicine
     Mayo Clinic
     Rochester, MN  55905
     [phone]

This disease entry is based upon medical information available through
January 1990.  Since NORD's resources are limited, it is not possible to keep
every entry in the Rare Disease Database completely current and accurate.
Please check with the agencies listed in the Resources section for the most
current information about this disorder.

Resources

For more information on Hunter Syndrome, please contact:

     National Organization for Rare Disorders (NORD)
     P.O. Box 8923
     New Fairfield, CT  06812-1783
     [phone]

     National MPS Society
     17 Kramer Street
     Hicksville, NY  11801
     [phone]

     MPS (Mucopolysaccharidoses) Research Funding Center, Inc.
     1215 Maxfield Road
     Hartland, MI  48029
     [phone]

     Society of Mucopolysaccharide Diseases, Inc.
     382 Parkway Blvd.
     Flin Flon, Manitoba, Canada R8A OK4

     Society of MPS Diseases
     30 Westwood Drive
     Little Chalfont, Bucks, England

     National Digestive Diseases Information Clearinghouse
     Box NDDIC
     Bethesda, MD  20892
     [phone]

For information on genetics and genetic counseling referrals, please
contact:

     March of Dimes Birth Defects Foundation
     1275 Mamaroneck Avenue
     White Plains, NY  10605
     [phone]

     Alliance of Genetic Support Groups
     35 Wisconsin Circle, Suite 440
     Chevy Chase, MD  20815
     (800) 336-GENE
     [phone]

References

MPS Society Brochure

MPS Research Funding Center Bulletin

BIRTH DEFECTS COMPENDIUM, 2nd ed.:  Daniel Bergsma, ed; March of Dimes,
1979.  Pp. 730.

MENDELIAN INHERITANCE IN MAN, 6th ed.:  Victor A. McKusick; Johns Hopkins
University Press. 1983. Pp. 836.