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$Unique_ID{BRK03876}
$Pretitle{}
$Title{Ichthyosis, X-Linked}
$Subject{Ichthyosis, X-Linked Steroid Sulfatase Deficiency DOC 2 Disorder of
Cornification 2 Ichthyosis Ichthyosis Congenita Ichthyosis Vulgaris }
$Volume{}
$Log{}

Copyright (C) 1988, 1989, 1991, 1992, 1993 National Organization for Rare
Disorders, Inc.

545:
Ichthyosis, X-Linked

** IMPORTANT **
It is possible the main title of the article (X-Linked Ichthyosis) is not
the name you expected.  Please check the SYNONYMS listing on the next page to
find alternate names and disorder subdivisions covered by this article.

Synonyms

     Steroid Sulfatase Deficiency
     DOC 2
     Disorder of Cornification 2

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

     Ichthyosis
     Ichthyosis Congenita
     Ichthyosis Vulgaris

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.


X-Linked Ichthyosis is a genetic skin disorder that affects males.  It is
an inborn error of metabolism characterized by a deficiency of the enzyme
steroid sulfatase.  This enzyme defect leads to several biochemical
alterations in the steroid sex hormone metabolism, including diminished
maternal estrogen production in late pregnancy.  Cholesterol sulfate may
accumulate in the blood and skin.  Normal functioning of sex hormones does
not appear to be affected.  Corneal opacities may be present, but do not
interfere with vision.

Symptoms

Symptoms of X-Linked Ichthyosis usually begin between 1 and 3 weeks of age.
The disorder is characterized by the development of brownish scales
(ichthyosis) that usually adhere tightly to the underlying skin.  Scales are
most prominent on the skin covering muscles, especially areas on one side of
the limbs (extensor muscles).  The scales may spread to the surfaces where
the flexing muscles are located.  However, the skin in the hollow of the
elbows and knees is usually affected less often than the back of the neck,
which is almost always scaly.  The face and scalp are usually free of scales,
but the trunk is often involved.  Palms of the hands and soles of the feet
are almost always spared.

Marked improvement of symptoms often occurs during the summer.

When they are giving birth to a male fetus who has X-Linked Ichthyosis,
women who are carriers of the disorder often experience a delay in labor and
sometimes difficulties with cervical dilatation.  Diminished estrogen
production often develops among female carriers when they are pregnant with a
male fetus who has this disorder.

Clouding of the eye's cornea may occur in about half of the men with X-
Linked Ichthyosis during adulthood.  Failure of the testicles to descend into
the scrotum may occur in approximately 12 to 25% of patients with X-Linked
Ichthyosis.  Additionally, these patients may be at increased risk to
contract malignancies of the testicles.

Causes

X-Linked Ichthyosis is a hereditary disorder transmitted by sex-linked genes.
Symptoms are caused by a deficiency of the enzyme steroid sulfatase.  (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

X-Linked Ichthyosis is a rare disorder affecting one in 2,000 males.  This
means there are 500 cases per million with 62,500 persons affected in the
United States, and occuring in about 1,865 births yearly.  Female carriers
may transmit the disorder without having any symptoms themselves.

Related Disorders

Symptoms of the following disorders may be similar to those of X-Linked
Ichthyosis.  Comparisons can be useful for a differential diagnosis:

"Ichthyoses" or "Disorders of Cornification" are general terms describing
a group of scaly skin disorders.  They are characterized by an abnormal
accumulation of large amounts of dead skin cells (squames) in the top layer
of the skin.  The conversion of an abnormally large number of epidermal cells
into squamous cells is thought to be caused by a defect in the metabolism of
the skin cells known as "corneocytes" or of the fat-rich matrix around these
cells.  The cells can be thought of as bricks, while the matrix would be the
mortar holding these cells together.  (See "Ichthyosis" in the Rare Disease
Database.)

Ichthyosis Congenita (Collodion Baby; Congenital Ichthyosiform
Erythroderma; Xeroderma; Desquamation of Newborn) is an inherited skin
disorder.  It is characterized by generalized, abnormally red, dry and rough
skin, with large, coarse scales.  Itchiness (pruritus) usually also develops.
Skin on the palms of the hands and soles of the feet is abnormally thick.
(For more information, choose "Ichthyosis Congenita" as your search term in
the Rare Disease Database.)

Other forms of Ichthyosis include Sjogren-Larsson Syndrome, Netherton
Syndrome, Ichthyosis Hystrix, Lamellar Ichthyosis, Refsum Syndrome, Darier
Disease, Conradi-Hunermann Syndrome, Chanarin-Dorfman Syndrome, Epidermolytic
Hyperkeratosis, etc.  (Search under each name for more information on that
disorder in the Rare Disease Database.)

Therapies:  Standard

X-Linked Ichthyosis can be diagnosed before birth by taking a few cells from
the fluid in the water sac that surrounds the fetus and testing these for
abnormalities.  This test is called amniocentesis.

X-Linked Ichthyosis is treated by applying skin softening (emollient)
ointments, preferably plain petroleum jelly.  This can be especially
effective after bathing while the skin is still moist.  Salicylic acid gel is
another particularly effective ointment.  The skin should be covered at night
with an airtight, waterproof dressing when this ointment is used.  Lactate
lotion can also be an effective treatment for this disorder.

Therapies:  Investigational

Drugs derived from Vitamin A (retinoids) such as tretinoin, motretinide, and
etretinate are often effective against X-Linked Ichthyosis, but can cause
toxic effects on the bones in some cases.  A synthetic derivative of Vitamin
A, isotretinoin, when taken by pregnant women, can cause severe birth defects
to the fetus.  These Vitamin A compounds have not yet been approved by the
Food and Drug Administration (FDA) for treatment of Ichthyosis.

The National Institute of Arthritis, Musculoskeletal and Skin Diseases is
looking for patients with various kinds of Ichthyosis willing to participate
in research aimed at mapping the genes responsible for their disorder.
Interested persons may contact:

     Dr. Sherri Bale
     National Institute of Arthritis, Musculoskeletal and Skin Diseases
     9000 Rockville Pike
     Bethesda, MD  20892
     [phone]

The orphan product Monolaurin (Glylorin) is being tested for the
treatment of X-Linked Ichthyosis.  The product is manufactured by:

     Cellegy Pharmaceuticals, Inc.
     371 Bel Marin Keys, Suite 210
     Novato, CA  94949

This disease entry is based upon medical information available through
May 1993.  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 X-Linked Recessive Ichthyosis, please contact:

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

     Foundation for Ichthyosis and Related Skin Types, Inc. (F.I.R.S.T.)
     P.O. Box 20921
     Raleigh, NC  27619-0921
     [phone]
     [phone]

     The National Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Information Clearinghouse
     Box AMS
     Bethesda, MD  20892
     [phone]

For genetic information 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

GENETICALLY TRANSMITTED, GENERALIZED DISORDERS OF CORNIFICATION.  THE
ICHTHYOSES:  M.L. Williams, et al.; Dermatol Clin (January 1987:  issue 5(1)).
Pp. 155-178.

THERAPEUTIC ACTIVITY OF LACTATE 12% LOTION IN THE TREATMENT OF
ICHTHYOSIS.  ACTIVE VERSUS VEHICLE AND ACTIVE VERSUS A PETROLEUM CREAM:  M.
Buxman, et al.; Journal Am Acad Dermatol (December 1986:  issue 15(6)).  Pp.
1253-1258.

THE METABOLIC BASIS OF INHERITED DISEASE, 5th ed.:  John B. Stanbury, et
al., eds.; McGraw Hill, 1983.  Pp. 1027-1039.

TOPICAL CHOLESTEROL TREATMENT OF RECESSIVE X-LINKED ICHTHYOSIS:  G
Lykkesfeldt, et al.;  Lancet (December 10, 1983:  issue 2(8363)).  Pp. 1337-
1338.