CD-ROM Today 1996 January/CD-ROM Today 1996 January.iso/dp/0382/03827.txt

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$Unique_ID{BRK03827}
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$Title{Holoprosencephaly}
$Subject{Holoprosencephaly Holoprosencephaly Sequence HS Alobar
Holoprosencephaly Familial Alobar Holoprosencephaly Lobar Holoprosencephaly
Semilobar Holoprosencephaly Holoprosencephaly Malformation Complex
Arhinencephaly Cleft Lip Cleft Palate }
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Copyright (C) 1991 National Organization for Rare Disorders, Inc.

791:
Holoprosencephaly

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

Synonyms

     Holoprosencephaly Sequence
     HS
     Alobar Holoprosencephaly
     Familial Alobar Holoprosencephaly
     Lobar Holoprosencephaly
     Semilobar Holoprosencephaly
     Holoprosencephaly Malformation Complex
     Arhinencephaly

Information on the following disease can be found in the Related
Disorders section of this report:

     Cleft Lip and Cleft Palate

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.

Holoprosencephaly is the failure of the prosenceplon section of the
forebrain (the part of the brain in the fetus that evolves into parts of the
adult brain) to develop.  This causes defects in the development of the
middle of the face and in brain structure and function.  Closely set eyes
(hypotelorism), missing front teeth (incisors), and an abnormally small head
(microcephaly) may occur.  Rarely, severely affected infants are born with
cyclopia (the eyes fused into one) and a deformed or absent nose.

Symptoms

Holoprosencephaly is a malformation sequence that can be mild or severe.
Many severely affected children are stillborn or die within a few days.  Some
mildly affected children may live for months or years.

Individuals affected mildly with Holoprosencephaly may have closely set
eyes (hypotelorism), missing front teeth (incisors), and an abnormally small
head (microcephaly).  Cleft lip and/or palate may also occur.  Mental
retardation also occurs.

Rarely, the most severely affected individuals may have cebocephaly or
cyclopia.  Cebocephalic individuals have a deformed or absent nose, and
either closely set eyes or cyclopia.  Cyclopia is the most severe and rarest
finding in Holoprosencephaly and is characterized by the fusion of the eyes
together.

Holoprosencephaly may also affect other systems in the body, including
absence of the pituitary gland.  An abnormally low concentration of glucose
(sugar) in the blood (hypoglycemia) may then occur.  Interruption of normal
breathing (apnea) and seizure disorders may also be present.  Males may have
an abnormally small penis (micropenis).

Causes

The exact cause of Holoprosencephaly is not known.  This birth defect occurs
alone in the majority of cases; however, certain chromosomal abnormalities
including Trisomy 13, 18p- and 13q- Syndromes, and Meckel-Gruber Syndrome,
should be considered.  A higher incidence of Holoprosencephaly has been
reported in children of diabetic mothers.  Cytomegalovirus (CMV) infection in
the fetus has also been associated with Holoprosencephaly.  Several reported
cases have involved parents who were related to each other.  Finally,
Holoprosencephaly can be inherited.  However, there is disagreement as to
whether it is transmitted through autosomal dominant or autosomal recessive
genes.  (For more information on these disorders, choose "Trisomy 13", "18p",
"13q", "Meckel-Gruber" or "Cytomegalovirus" as your search terms in the Rare
Disease Database).

Human traits, including the classic genetic diseases, are the product of
the interaction of two genes, one received from the father and one from the
mother.

In dominant disorders a single copy of the disease gene (received from
either the mother or father) will be expressed "dominating" the other normal
gene and resulting in appearance of the disease.  The risk of transmitting
the disorder from affected parent to offspring is fifty percent for each
pregnancy regardless of the sex of the resulting child.

In recessive disorders, the condition does not appear unless a person
inherits the same defective gene for the same trait from each parent.  If one
receives one normal gene and one gene for the disease, the person will be a
carrier for the disease, but usually will show no symptoms.  The risk of
transmitting the disease to the children of a couple, both of whom are
carriers for a recessive disorder, is twenty-five percent.  Fifty percent of
their children will be carriers, but healthy as described above.  Twenty-five
percent of their children will receive both normal genes, one from each
parent, and will be genetically normal.

Affected Population

Holoprosencephaly is a very rare disorder affecting males and females in
equal numbers before birth.  The incidence of Holoprosencephalic children
with normal chromosomes has been estimated at between 1 in 16,000 and 1 in
53,394 live births.

Related Disorders

Holoprosencephaly usually includes mental retardation and cleft lip or
palate.  There are many birth defects in which mental retardation is a
symptom.  (For more information, choose "Mental Retardation" as your search
term in the Rare Disease Database).

Cleft lip and cleft palate are among the most common birth defects found
in newborn infants.  A cleft occurs when the roof of the mouth is not
completely closed at birth.  This opening or fissure is due to a failure of
the upper jaw bones (maxillae) to properly fuse together during development
of the embryo.  This deformity may affect the entire roof of the mouth
(palate), the lip, or both.  The severity of the cleft may range from a
barely visible notch to complete non-closure and deformity of the lip and
palate.  It may be inherited as an autosomal dominant trait, it can be a
symptom of other birth defects, or it may involve a complex genetic pattern
not understood as of yet.  (For more information on this disorder, choose
"Cleft" as your search term in the Rare Disease Database).

Therapies:  Standard

The presence of Holoprosencephaly can be detected prenatally through
ultrasound.  Prenatal chromosomal examination of subsequent pregnancies may
be indicated.  Computerized tomography may be used to determine the severity
of the Holoprosencephaly.

Pediatricians, dentists, special education teachers, surgeons, speech
pathologists, psychologists and others must systematically and
comprehensively plan the child's treatment for Holoprosencephaly.  Plastic
reconstructive surgery of the face may be considered in some cases.

Genetic counseling may be of benefit for patients and their families.
Family members of children with Holoprosencephaly should be carefully
examined for mild symptoms such as a single front tooth (incisor) instead of
two, and closely-set eyes (hypotelorism).  Other treatment is symptomatic and
supportive.

Therapies:  Investigational

This disease entry is based upon medical information available through March
1991.  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 Holoprosencephaly, please contact:

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

     National Institute of Child Health & Human Development (NICHHD)
     9000 Rockville Pike
     Bethesda, MD  20892
     [phone]

     Fighters for Encephaly Defects Support Group
     3032 Brereton Ave.
     Pittsburgh, PA  15219
     [phone]

     Society for the Rehabilitation of the Facially Disfigured
     550 First Ave.
     New York, NY  10016
     [phone]

     Association For Retarded Citizens of U.S.
     P.O. Box 6109
     Arlington, TX  76005
     [phone]
     1-800-433-5255

For genetic information and genetic counseling referrals:

     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

SMITH'S RECOGNIZABLE PATTERNS OF HUMAN MALFORMATION, 4th ed.:  Kenneth L.
Jones;  W.B. Saunders Co., 1988.  Pp.546-7.

MENDELIAN INHERITANCE IN MAN, 8th ed.:  Victor A. McKusick; Johns Hopkins
University Press, 1986.  Pp. 987.

SONOGRAPHY OF FACIAL FEATURES OF ALOBAR AND SEMILOBAR HOLOPROSENCEPHALY:
J.P. McGahan, et al.;  AJR Am J Roentgenol (January, 1990, issue 154(1)).
Pp. 143-8.

HOLOPROSENCEPHALY:  A DEVELOPMENTAL FIELD DEFECT:  V.P. Johnson;  Am J
Genet (October, 1989, issue 34(2)).  Pp. 258-64.