What Is Cystinosis

Cystinosis is a rare, genetic disease, which is diagnosed early in childhood, usually before the age of two. It is autosomal recessive, which means that it is inherited when a child receives two copies of an abnormal gene, one copy from each parent. Because the parents each have only one abnormal gene, they are not affected.

It is estimated that cystinosis occurs in somewhere between 1 in 100,000 to 1 in 200,000 live births. There are 2 or 3 new cases of cystinosis diagnosed each year in the UK.

The problem in cystinosis is an increase in many parts of the body of a natural chemical, an amino acid called cystine. This build up causes cystine crystals to form in many organs of the body.  These crystals form firstly in the kidneys and the eyes, and later in the muscles, pancreas, thyroid gland and white blood cells.

There are three different types of cystinosis:
1. Nephropathic infantile cystinosis which starts by affecting the kidneys in babies and children under the age of 2 (90-95% of all cases)
2. Nephropathic juvenile cystinosis which starts by affecting the kidneys in young children (3-5% of all cases)
3. Ocular cystinosis which affects the eyes and does not cause problems until later in life (the rarest form with only 1-2% of all cases)


The Clinical Picture

As well as problems with the kidneys and the eyes, later it can affect the pancreas (causing diabetes), lead to an underactive thyroid, and cause muscle wasting.  There are other organs and systems which can sometimes be involved. The symptoms and their severity will vary from person to person, but below you will find some of the more common issues:
Following an event free pregnancy and birth families notice that their young infant experiences excessive thirst and urination, as well as vomiting, difficulty feeding and poor growth (this is often described as failure to thrive).  The GP will refer to a paediatrician, who sends the family to a kidney doctor ( a nephrologist), who suspects a Fanconi Syndrome.  The Fanconi Syndrome means the kidneys do not properly absorb vitamins, various salts and minerals.  This often leads to a diagnosis of cystinosis.

Without specific treatment, most children with cystinosis will later develop kidney failure before the age of ten requiring dialysis or a kidney transplant.
The build-up of crystals can make the eyes sore, sensitive to light and gives the feeling that grit or dust has got into the eyes.  Vision can become blurred or hazy.
Muscles and Bones:
The kidney problem (Fanconi Syndrome) can cause a softening or weakening of the bones, otherwise known as rickets.

Accumulation of cystine can also cause weakness and wasting of the muscles.  When this happens in the throat, there can be swallowing and feeding difficulties, and in the chest, the lungs can be affected causing breathing difficulty.

Despite these many problems, a better understanding of cystinosis and earlier treatment mean that organ damage can be significantly reduced and people with cystinosis can enjoy a longer, fuller life.


How is Cystinosis Treated?

In the UK, there are a number of doctors who know how to diagnose and look after people with cystinosis.  Sometimes, people with cystinosis may have to travel a long way to see an expert.  A nephrologist oversees most of the treatments, but several other medical specialists can be involved as well, such as eye doctors (ophthalmologists), doctors who specialise in the brain (neurologists), those who know about growth, thyroid and diabetes (endocrinologists), clinical geneticists, as well as specialist nurses.  Whilst visiting hospitals for appointments with doctors, people with cystinosis will need regular blood tests to check on the response to treatment.

There are many symptomatic treatments for people with cystinosis that help problems with the kidneys, bones, growth and muscles.  People generally have to take several different medicines, including those to treat their kidney problems (electrolytes, vitamins) and to improve growth (including growth hormone).

Since the 1990’s, a medicine called cysteamine has been used to lower cystine levels within the cells of the body and so reduce the organ damage this causes.  Cysteamine has proven to be effective in delaying or preventing kidney failure, and also improves the growth of children with cystinosis. Cysteamine is a lifelong treatment. There are two formulations of cysteamine capsules available in the UK, as well as cysteamine eye drops that help to dissolve cystine crystals in the cornea of the eye.

People living with cystinosis should discuss all these treatment options with their expert doctor.

The Cystinosis Foundation UK is pleased to give help, information and support to anyone living with or caring for people with cystinosis in the UK.

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