About Cystinosis

About Cystinosis

About Nephropathic Cystinosis

 

WHAT IS CYSTINOSIS?

Cystinosis is a rare, genetic condition that affects an estimated 2,500 worldwide.

Cystinosis symptoms usually appear within a child’s first year of life.

 

    • In people with cystinosis, cystine (an amino acid) builds up in the body’s cells and the cells are unable to remove it
    • When cystine builds up, it forms cystine crystals within cells that can lead to long- term damage to the body’s organs—including the kidneys, eyes, liver, muscles, pancreas, and brain
    • This damage cannot be reversed, but it can be delayed or reduced

There are 3 forms of cystinosis:

      • Nephropathic (or infantile) cystinosis is the most prevalent and severe form of cystinosis
      • Intermediate (or juvenile) cystinosis is characterized by slower disease progression
      • Nonnephropathic (or ocular) cystinosis affects the eyes but does not present in other body systems

Nephropathic cystinosis presents within a child’s first year.

Signs & Symptoms

Cystinosis is the most common inherited cause of Fanconi syndrome.  Laboratory testing in blood may reveal severe electrolyte abnormalities, including low potassium, low phosphors and low bicarbonate. 

Cystinosis symptoms commonly present in otherwise healthy infants within the first year of life. Parents primarily note frequent wet diapers (polyuria) and persistent thirst (polydipsia, resulting in dehydration) when first describing their child’s symptoms.

Initial cystinosis symptoms are commonly the result of cystine accumulation in the kidney tubules, which results in Fanconi syndrome. Fanconi syndrome involves cellular atrophy of the proximal renal tubules, giving “swan neck” like deformities.

Cystinosis is the most common identifiable cause of renal Fanconi syndrome in children. If untreated, this will lead to end-stage renal disease, requiring a kidney transplant by age 10 years.

Within infants’ first 6-12 months, the eyes are commonly affected and become photosensitive, and the bones can develop rickets.

  • Failure to thrive
  • Dehydration
  • Underweight
  • Soft bones (Rickets)
  • Unquenchable Thirst
  • Sensitivity to light

How cystinosis affects the body

Cystinosis can affect nearly every organ of the body.  Cystinosis treatment can prevent or slow some effects, but existing damage cannot be reversed.

Symptomatic treatment (before kidney failure develops)

It is possible to relieve some of the kidney symptoms by ensuring that you drink an adequate amount of water to replace the excessive fluid loss.

Taking supplements will replace the sodium, bicarbonate, and potassium being leaked by the kidneys. The amount of supplements you take may vary according to your blood results. Vitamin D and phosphorus supplements will heal and prevent bone diseases.

Cystinosis specific treatment

  • There is currently no complete cure for cystinosis. The aim of specific treatment is to reduce the amount of cystine within the cells.
  • Cysteamine is a cystine-depleting drug which reduces the level of cystine within the lysosomes.
  • Cysteamine is most effective when taken four times a day at six-hourly intervals. This medication is a life-long treatment and is taken every day.
  • Cysteamine treatment is very important as it reduces the progression towards kidney failure. It is not an easy medicine as it has a smell that some people find unpleasant and has to be taken regularly in the long term.
  • Cysteamine is still effective even after kidney failure has developed. It prevents other organs in the body being damaged and can prevent further damage to the pancreas and liver.
  • Eye drops containing cysteamine can prevent damage to the eye and can help with photophobia (discomfort in bright light). These need to be applied several times a day to prevent cystine crystals forming.

Treatment monitoring

It is possible to measure the effectiveness of treatment by taking a white blood cell (WBC) cystine level. This is a blood test that allows us to measure the amount of cystine accumulating in the cells and should be checked every 3–4 months.
To prevent damage to your organs, the level should be kept below 1.0. Blood samples should be taken 5–6 hours after taking cysteamine.
It is important to let your healthcare professional know if you are missing any doses of cysteamine.

THE CAUSE OF CYSTINOSIS

Cystinosis is a genetic inherited disease and is not infectious, contagious, or brought on by lifestyle.

We have thousands of genes, each carrying their own set of instructions. When a gene is altered, it can result in a genetic condition or disease. We all have two copies of each gene—one inherited from our mother and one inherited from our father.

Cystinosis is inherited in a way that is called recessive. This means that individuals must inherit two copies of the altered gene to be affected by cystinosis. Individuals who inherit one copy of the altered gene are completely healthy and are known as carriers.

When both parents are carriers of the same altered gene, there are four possible outcomes for each pregnancy (see diagram below).

Each child of parents who both carry the cystinosis gene has a 25% chance of inheriting a changed gene from both parents and being affected by cystinosis.

There is a 50% chance that the child will inherit just one copy of the cystinosis gene. This means they will be healthy carriers like their parents.

There is a 25% chance that the child will inherit both normal copies of the gene and will not have cystinosis or be a carrier of cystinosis.

Now, depending on the CTNS gene mutation, three types of cystinosis can develop that differ in the age of onset and severity of symptoms. They are nephropathic (or infantile), late-onset, and ocular.
In general, humans have two copies of their genes, so both must be damaged for there to be so little cystine transport that cystinosis occurs. That means that a person with cystinosis must receive a mutated CTNS gene from both the mother and father. For each such mating, there's a 25% chance that both parents will pass down their own CTNS mutation to their offspring.
Now, in cystinosis, any one of over 100 mutations can affect the CTNS gene, leading to a defective cystine transporter. Without a working transporter, cystine has no way of leaving the lysosome. So it accumulates, turning into cystine crystals in the process—crystals that slowly damage organs like the kidneys and eyes.

RESOURCES

Having social support may help to improve patient well-being and foster the ongoing ability to manage challenges.

 

Cystinosis Research Network logo

Cystinosis Research Network / www.cystinosis.org

Cystinosis Research Network is dedicated to supporting and advocating for research, providing family assistance, and educating the public and medical community about cystinosis.

Cystinosis Research Foundation logo

Cystinosis Research Foundation / www.cystinosisresearch.org

The Cystinosis Research Foundation is dedicated to finding better treatments and ultimately a cure for cystinosis, and to educating the public and medical community to ensure early diagnosis and proper treatment.

 

National Organization for Rare Diseases logo

The National Organization for Rare Disorders (NORD) / www.rarediseases.org

NORD is a patient advocacy organization dedicated to individuals with rare diseases and the organizations that serve them. NORD, along with its more than 300 patient organization members, is committed to the identification, treatment, and cure of rare disorders through programs of education, advocacy, research, and patient services.

 

Center for Chronic Illness logo

The Center for Chronic Illness / www.thecenterforchronicillness.org

The Center for Chronic Illness sponsors a web-based support group for adults with cystinosis called Living with Cystinosis.

Disclaimer:

The information presented above is intended for general education purposes only, and should not be construed as advising or diagnosis or treatment of this or any other medical condition.