Rare diseases are not so rare, because they affect approximately 4 million people in Germany alone and 30 million in the European Union. A disease is considered rare if it does not affect more than five in 10,000 people. Many of these diseases are genetic, starting after birth or in early childhood, and most cannot be cured. The lifespan and quality of life of the patients are mostly reduced. Around 7,000 to 8,000 diseases are currently known as rare or so called „orphan diseases”.
Cystinosis is a very rare condition. Around 80 to 135 patients are estimated to be affected in Germany. The estimated prevalence is one patient per 150,000-200,000 newborns.
There are three types of this disease:
- Infantile nephropathic cystinosis – the most common and most severe form which accounts for 95% of the cases
- Juvenile cystinosis – which starts later and is not as difficult
- Ocular cystinosis – which is limited to the eyes only.
This disease is a lysosomal metabolic disorder. Lysosomes are cell organelles that digest and remove foreign material. Cystine is an amino acid. In cystinosis, cystine cannot be removed from the lysosomes, which leads to an accumulation first, then to a loss of the lysosome and subsequently to the whole cell. This process takes place in almost all body cells, which explains why almost all organs are affected by this disease. The kidney is the most severely affected organ, but also the eyes, muscles, bones, endocrine organs (e.g. the thyroid gland), the central nervous system, etc. are affected. The disease lasts for life, it is incurable.
It is an autosomal recessive disorder in which both the mother and the father carry the afflicted gene (CTNS gene) on a chromosome (chromosome region 17p13). The parents are (heterozygous) gene carriers and therefore healthy. The disease only develops if both dysfunctional genes are transmitted to the child. The likelihood that the child is homozygous, that is to say that both sick genes are inherited from the parents, lays at 25%.
Therapy / survival
The most severely affected organ is the kidney. No therapy was available until the early 1980s. Until then, children usually died of terminal renal failure by the age of 10. In 1985, cysteamine was introduced as the only drug for this disease to date. A big disadvantage of this medication is that it is a sulfur compound, which is responsible for an unpleasant smell of the patient. This therapy must be taken lifelong.
Thanks to the option of kidney replacement therapy in the form of dialysis or kidney transplantation and drug therapy, patients can survive today.
The disease begins during pregnancy, although the babies initially show no abnormalities after birth.
A serious loss of salt and electrolyte develops between the age of 12 to 24 months, leading to weight and growth disorders. When diagnosed, most children are already so sick that they need a gastrointestinal probe for nutrition and growth hormones later on.
In addition to the kidney, the eyes are affected by cystine crystal deposits in the cornea. To avoid this, the patient must apply cysteamine eye drops 4-6 times daily to remove the crystals from the cornea.
Also typical for the disease is the involvement of the muscles, which leads to muscle atrophy (decrease in muscles) and hypotrophy (muscle weakness). The decline in the muscles can be seen early in the ball of the thumb (thenar hypotrophy). Everyday life can be significantly more difficult due to muscle weakness, e.g. bottles and yoghurt glasses can no longer be opened. The disease and the involvement of other organs such as the thyroid gland (hypothyroidism), the bones etc. are shown under medical information.
The point in time that dialysis is mandatory depends on the time of the diagnosis. The later the patient is diagnosed, the sooner he will need kidney replacement therapy. So far, the diagnosis cannot be made within the framework of the established newborn screening, which is why we have launched a model project.
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