Brochure
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Facts About Cystinosis
- What is Cystinosis?
- Cystinosis is a metabolic disease characterized by an abnormal
accumulation of the amino acid cystine in various organs of the body such as
the kidney, eye, muscle, pancreas, and brain. Different organs are affected at
different ages.
- Is it Inherited?
- The disease is inherited in an autosomal recessive fashion, meaning
that each parent of a child with cystinosis carries one defective gene and one
normal gene. The parents never have any signs of the disease.
- What Causes Cystinosis?
- The cystine content of cystinotic cells averages 50-100 times the
normal value. The cause is a defect in the transport of cystine out of a cell
compartment called the lysososme, in which cystine accumulates. Because of
cystine's low solubility, this amino acid forms crystals within the lysosomes
of cells, and this is probably what destroys the cells.
- What are the symptoms?
- There are three clinical forms of cystinosis. Infantile (or
nephropathic) cystinosis; late-onset cystinosis; and benign cystinosis. The
latter form does not produce kidney damage. Infantile and late-onset cystinosis
differ in the age of appearance of the first symptoms and in the rapidity of
the clinical course. Infantile cystinosis is usually diagnosed between 6 and 18
months of age with symptoms of excessive thirst and urination, failure to
thrive, rickets, and episodes of dehydration. These findings are caused by a
disorder called renal tubular reabsorb nutrients and minerals. As a
consequence, these important molecules are lost in the urine. Children with
cystinosis also have crystals in their eyes (after one year of age) and an
increased level of cystine in their white blood cells. Without specific
treatment, children with cystinosis develop end-stage renal failure, i.e., lose
their kidney function, at approximately 9 years of age.
- If cystinosis patients receive a kidney transplant and reach
adulthood, their new kidney will not be affected by the disease. However,
without cysteamine treatment (see below), they can develop complications in
other organs due to the continued accumulation of cystine throughout the body.
These complications can include muscle wasting, difficulty swallowing,
diabetes, hypothyroidism, and blindness. Not all older patients develop these
problems, however.
- Can Cystinosis Be Treated?
- The symptomatic treatment of the Fanconi syndrome is
essential. The urinary losses of water, salts, bicarbonate, and minerals must
be replaced. Most children receive a solution of sodium and potassium citrate,
as well as phosphate. Some also receive extra vitamin D.
- The aim of specific treatment for cystinosis is to
reduce cystine accumulation within the cells. This goal is achieved by
cysteamine treatment, which has proven effective in delaying or preventing
renal failure. Cysteamine also improves growth of cystinosis children. The Food
and Drug Administration (FDA) has approved a capsule form of cysteamine called
CYSTAGON
.
- Kidney transplantation has proven very helpful in patients with
cystinosis, and cysteamine therapy should be considered to try to prevent the
late complications of the disease (see above).
- For both young children with cystinosis and older patients with a
kidney transplant, cysteamine eyedrops may be available to remove the corneal
cystine crystals. However, these are not yet approved by the FDA.
- Is Prenatal Detection Available?
- Today, prenatal diagnosis is available for families known to be at
risk for having a child with cystinosis. Chorionic villus sampling is performed
at 8-9 weeks of gestation; amniocentesis can be performed at 14-16 weeks of
gestation.
- What are Possible Future
Developments?
- Much remains to be learned about cystinosis. Investigators are trying
to identify the abnormal gene which causes this condition. Other investigators
are trying to determine the best therapies for each complication. Some
questions which remain include:
- Will children with cysteamine from infancy be spared all of
the later complications of cystinosis?
- Will they avoid kidney transplantation entirely?
- Will cysteamine benefit patients who begin therapy after
receiving a kidney tranplant?
- Can cysteamine eye drops be approved by the Food and Drug
Administration?
- Will scientists discover the precise mechanism by which the
cystinosis gene product rids lysosomes of cystine?
William A. Gahl, M.D., Ph.D.
National Institutes of
Health
Bethesda, Maryland
1998 Revision
-
How Can You Help?
-
- With your tax-deductible contribution.
- Become a volunteer and use your talents to further the goals of
the Foundation.
- Become a member of the
Cystinosis Foundation
Send your donations or requests for further information
to:
CYSTINOSIS FOUNDATION
604 Vernon Street
Oakland, CA
94610
What is the Cystinosis
Foundation?
The CYSTINOSIS FOUNDATION is an all volunteer, non-profit organization
dedicated to providing services for those suffering from cystinosis by:
- Parental Support - Parents are given information and referrals,
receive Newsletters and are invited to Foundation
sponsored Conferences.
- Education - The medical profession and the general public are
educated about this rare disease through receptions at medical meetings, the
media and distribution of literature.
- Research Support - The Foundation raises funds to promote research on
causes and treatments of cystinosis.
- Affiliations - The Foundation is a member of the National Organization of Rare Disorders (NORD), which
furthers the cause of those with rare diseases and the Alliance of Genetic
Support Groups.
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Information presented in this brochure is intended
for general
education purposes only, and
should not be construed as advising or
diagnosis or
treatment of this or any other medicla condition.