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Cystinosis, One of 7,000
Rare Diseases
By Terri Schleuder
VP of Education & Awareness, Cystinosis Research Network
Statistically, there are over 7,000 rare diseases in the United
States that collectively impact 30,000,000 people. This is the
story about one of them, and an important one for kidney
disease patients as nearly all cystinosis patients lose their
kidney function. Also, recent data suggests a high incidence
of underdiagnosis and carriers among dialysis patients.
Nephropathic Cystinosis is a rare metabolic, genetic disease that
affects about 500 people in the U. S. and about 2,000 worldwide.
Cystinosis occurs in a child when he/she inherits the recessive
gene, identified in the late 1990’s as the CTNS gene, from each
parent. In the general population, only 1 in 200 people carry
this gene -- but if two carriers of the CTNS gene produce a child,
there is a 25% chance that the child will have Cystinosis. This occurs in about 1 of every 250,000 births. It is very rare!
Our family became one of these statistics when our youngest son, Steve, was born in 1988.
The defect that causes Cystinosis is at the cellular level. Cystinosis occurs when an amino acid called cystine gets trapped
inside a part of the cell called the lysosome. Think of it as a
one-way door. The cystine gets into the lysosome, but because
of the defect it cannot get back out. This causes a build-up of
cystine that forms crystals within the cell that damages and
eventually destroys cell function.
Virtually all the cells are impacted in Cystinosis and eventually many organs in the body are damaged. The kidney and
Adults with Cystinosis at the 2015 CRN Family Conference held in Chicago in July.
Steve is seated, the first one on the right.
eye are more severely damaged early on. In the kidney, the
ability to reabsorb water and crucial electrolytes (such as sodium, potassium, bicarbonate and others necessary for normal body functioning) are lost, spilling out into the urine. This
process is called Fanconi Syndrome. Cystinosis is the leading
cause of Fanconi Syndrome in children. In the eye, the cystine
forms crystals in the cornea that cause severe photophobia
(sensitivity to light) and painful corneal ruptures. Left untreated, blindness can result.
Hallmarks of Infantile Nephropathic Cystinosis in the first
year of life are dehydration, polyuria (need to pass a lot of
urine every day) and an unquenchable thirst. Due to the kidneys’ inability to balance calcium and phosphorus, infant’s
bones do not develop normally, resulting in Rickets. Infants
with Cystinosis often have no appetite, though what is consumed is usually salty or spicy. Infants may experience frequent vomiting (2-5 times daily). Children
who appeared normal at birth, stop growing, lose
weight and quickly fall below the 3rd percentile on
growth charts. This is called failure to thrive.
Teens with Cystinosis attending the Global Genes sponsored Teen Adventure as part of the CRN
Family Conference in Chicago. Dr. William Gahl and Dr. Craig Langman are holding the sign.
Our son, Steve, began to show all of these symptoms between 6 and 9 months of age. He progressively got worse as time passed. Repeated trips to
doctors and specialists yielded more questions than
answers. In July 1989, when he was 18 months old,
his weight had dropped to less than 15 lbs. His skin
hung in loose folds. His hair had started to fall out.
His huge blue eyes had big dark circles under them
and his lips and mouth were always dry, no matter
how much water he drank (which was a lot, more
than an adult).