CD-ROM Today 1996 January/CD-ROM Today 1996 January.iso/dp/0412/04126.txt

Text File | 1994-01-17 | 10KB | 236 lines

$Unique_ID{BRK04126}
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$Title{Porphyria Cutanea Tarda}
$Subject{Porphyria Cutanea Tarda PCT Porphyria Cutanea Tarda Symptomatica
Porphyria}
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Copyright (C) 1987, 1988, 1990 National Organization for Rare Disorders, Inc.

321:
Porphyria Cutanea Tarda

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

Synonyms

     PCT
     Porphyria Cutanea Tarda Symptomatica
     Porphyria

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.


Porphyria Cutanea Tarda (PCT) is the most common of the porphyrias.  It
results from a deficiency of the enzyme uroporphyrinogen decarboxylase
(URO-D).  The disorder can be caused by either inherited or acquired factors.
PCT is one of the "hepatic" porphyrias, and large amounts of porphyrins can
build up in the liver when the disease is active.  When inherited, the enzyme
deficiency is inherited as an autosomal dominant trait.  In most individuals
with the inherited enzyme deficiency, the disease remains latent and may never
be symptomatic.

The porphyrias are a group of at least seven disorders.  The common
feature in all porphyrias is the excess accumulation in the body of
"porphyrins" or "porphyrin precursors."  These are natural chemicals that
normally do not accumulate in the body.  Precisely which one of these
porphyrin chemicals builds up depends upon the type of porphyria that a
patient has.

Porphyrias can also be classified into two groups:  the "hepatic" and
"erythropoietic" types.  Porphyrins and related substances originate in
excess amounts from the liver in the hepatic types, and mostly from the bone
marrow in the erythropoietic types.

The porphyrias with skin manifestations are sometimes called "cutaneous
porphyrias."  The "acute porphyrias" are characterized by sudden attacks of
pain and other neurological manifestations.  These "acute" symptoms can be
both rapidly appearing and severe.  An individual may be considered in a
"latent" condition if he or she has the characteristic enzyme deficiency but
has never developed symptoms.  There can be a wide spectrum of severity
between the "latent" and "active" cases of any particular type or porphyria.

The symptoms and treatments of the different types of porphyrias are not
the same.  For more information on the other forms of this disorder, choose
"porphyria" as your search term in the Rare Disease Database.

Symptoms

The symptoms of Porphyria Cutanea Tarda are usually confined to the skin.
Blistering after exposure to sunlight and/or minor trauma may occur on the
hands, face and other sun-exposed areas.  Increased hair growth, and
darkening and thickening of the skin may also occur.  Neurological and
abdominal symptoms are not characteristic of PCT.  Liver function
abnormalities are common but are often mild.

Porphyria Cutanea Tarda is the only type of porphyria that can be either
acquired or inherited.  All other types of porphyria are caused by genetic
factors.

The terms "porphyrin" and "porphyria" are derived from the Greek word
"porphyrus," meaning purple.  Urine from some porphyria patients may be
reddish in color due to the presence of excess porphyrins and related
substances, and the urine may darken after being exposed to the light.

The symptoms of porphyria generally arise from effects on the nervous
system and/or the skin.  Sometimes, the effects on the nervous system are not
clear, and proper diagnosis is delayed.  Skin manifestations can include
burning, blistering and scarring of sun-exposed areas.

Causes

Porphyria Cutanea Tarda (PCT) results from a deficiency of the enzyme
uroporphyrinogen decarboxylase (URO-D) which can be caused by either
inherited or acquired factors.  A nutritional disorder may also be a
contributing factor in PCT.

Environmental factors may include drugs, chemicals, diet and sun
exposure.  Depending on the type of porphyria, these factors can greatly
influence the severity of symptoms.

Because all porphyrias are uncommon, it is very unlikely that more than
one type will occur in the same family, or that someone with one type of
porphyria will go on to develop another.

Affected Population

Porphyria Cutanea Tarda is more common in males, and usually occurs late in
life.  It is also found with unusually high prevalence in the Bantu people of
southern Africa who also tend to have nutritional cirrhosis of the liver.

Related Disorders

The Porphyrias are a group of related disorders.  For more information on
each of the following types of the disease, choose "porphyria" as your search
term in the Rare Disease Database.

ALA-D Porphyria is a recently-described form of acute porphyria inherited
as an autosomal recessive trait.  It is apparently extremely rare.  There is
a deficiency of the enzyme delta-aminolevulinic acid dehydratase (ALA-D) and
increased excretion of ALA in the urine of patients with this type of
porphyria.

Acute Intermittent Porphyria is a dominant hereditary disorder.  A
usually latent form of porphyria, it may be provoked into active disease by
the administration of certain drugs, notably barbiturates, sulfonamides, and
estrogen compounds.

Congenital Erythropoietic Porphyria (CEP) is a hereditary disorder due to
an inborn error of metabolism, and manifested in infancy.  Faulty conversion
of the enzyme PBG to uroporphyrinogen in erythroid cells of bone marrow, and
red blood cells leads to this form of porphyria.  Increased porphyrins also
may be found in plasma, urine, feces, teeth and bones.

Hereditary Coproporphyria (HCP) is a latent type of porphyria similar to
Acute Intermittent Porphyria, although usually less severe.  This disorder is
due to an enzyme deficiency.  Some patients may develop skin
photosensitivity.  Attacks are usually precipitated by exposure to drugs such
as barbiturates, tranquilizers, anticonvulsants, and estrogens.

Variegate Porphyria (VP) is a hereditary type of porphyria due to an
inborn error of metabolism.  Precipitating or aggravating factors may include
exposure to barbiturates, sulfonamides, general anesthetics, excessive
amounts of ethanol, and estrogens.

Erythropoietic Protoporphyria (EPP) is a hereditary type of porphyria
marked by an accumulation of protoporphyrin in the bone marrow, red blood
cells and sometimes the liver.  Excess protoporphyrin is excreted by the
liver into the bile, which in turn enters the intestine and is excreted in
the feces.  There are no urinary abnormalities.  The diagnosis is established
by finding increased protoporphyrin in red blood cells, plasma and feces.

Therapies:  Standard

The orphan drug Hematin (an intravenous drug) is very potent in suppressing
acute attacks of the disease.  It is usually given only after a trial of
glucose therapy.  Attention should be given to salt and water balance during
treatment.

Many types of drugs such as aspirin and certain antibiotics are believed
to be safe in patients with some types of porphyria.  Recommendations about
drugs for certain types of porphyrias are based on experience with the
porphyria patients in whom attacks have been caused by drugs and by tests in
animals.  Since many commonly used drugs have not been tested, they should be
avoided if at all possible.  If a question of drug safety arises, a physician
or medical center specializing in porphyria should be contact.  A list of
these institutions may be procured from the American Porphyria Foundation.

Pregnancy is tolerated much better than was formerly believed.  Many
patients have a few reservations about family planning.  For those who do,
genetic counseling may be useful.

Wearing a Medic Alert bracelet is advisable in patients who have had
attacks, but is probably not warranted in most latent cases.

Therapies:  Investigational

New treatments for several types of porphyria are under investigation.  For
the most updated information on research, please contact the organizations
listed in the Resources section.

Dr. Anderson at the University of Texas Medical Branch, Department of
Preventive Medicine, Route J09, Galveston, TX 7550 has received a grant from
the FDA for investigation of the orphan drug Erythropoietin in the treatment
of Porphyria Cutanea Tarda in patients on long-term hemodialysis.

This disease entry is based upon medical information available through
March 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 Porphyria Cutanea Tarda, please contact:

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

     American Porphyria Foundation
     P.O. Box 22712
     Houston, TX  77227
     [phone]

     Porphyria Support Group
     4 Eve Road
     Leytonstone, London, England
     E11 3JE
     Tel:  [phone]

     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

American Porphyria Foundation brochure, "Common Questions About Porphyria."