Re: What is cystonosis?

Hi Amy,
There's a really good reason why you couldn't find anything on Cystinosis
-- in the United States only 400 people are affected, making it one of the
most rare genetic diseases out there!  It is inherited in an autosomal
recessive pattern, and the gene responsible is found on chromosome 17.

Cystinosis is actually more commonly known as one of the causes of Renal
Fanconi Syndrome, which is a collection of symptoms involving impaired
kidney function including polyuria (excessive urination), polydipsia
(excessive thirst), and hypokalemia (abnormally low levels of potassium in
the blood).  Individuals with Cystinosis also suffer from retarded growth
and poor appetite, as well as abnormal sensitivity to light and loss of
color in the retina of the eyes.

 The specific defect associated with Cystinosis is a mutation in the gene
that codes for the lysosomal cystine transporter. Cystine is an amino acid
found in many proteins. Lysosomes, which are membrane bound particles
within cells, aid in intracellular digestive function.  Cystinosis is
characterized by the accumulation of cystine in the lysosomes of tissues
throughout the body, which can cause certain organs, the kidneys in
particular, to malfunction.  If left untreated, the disease may lead to
kidney failure by 10 years of age.  The eye problems associated with
Cystinosis are caused by crystallization of cystine in the cornea of the
eyes.

Three forms of Cystinosis are recognized. Infantile Nephropathic
Cystinosis is the most severe form of the disease, and symptoms appear as
early as 6 to 12 months after birth. In people with Intermediate
Cystinosis or Juvenile (Adolescent) Cystinosis, kidney and eye symptoms
typically become apparent during the teenage years or early adulthood.  A
form of the disease known as Benign or Adult Cystinosis is associated more
with corneal problems than with kidney malfunction.

Treatments of the disease are really quite diverse.  To combat the
excessive loss of salts in urine, electrolyte replacement therapy is given
(sodium and potassium salts).  Patients also drink large amounts of water
to prevent dehydration.  A more direct therapy is to treat with
aminothiols (specifically a drug called Cystagon), which deplete the
lysosomes of cystine.  Cystinosis patients can also become hypothyroid
(their thyroid glands are not active enough) so they are given hormone
replacement therapy.  Because children with cystinosis are often very much
shorter than other children their age, they are also commonly placed on
growth hormone therapy as well.

So you now know a lot more than most people do about this disease; even
most of the doctors I know had no idea what cystinosis is.  That was a
great question -- keep them coming!

:)Carolyn