What is Cystinosis?

Cystinosis is a rare, genetic metabolic condition that affects every cell in the body

How rare is it? It is estimated that only about 500 people in the United States and 2,000 people worldwide are currently diagnosed with cystinosis.1 The condition is so rare that most people have never heard of it. In the past, some people with cystinosis never got the chance to meet another person with the condition, and families never met other families. Now there are support groups and organizations to help raise awareness and connect people.

What does genetic mean? This means it’s in your DNA. The genes from your parents combined in a way that made cystinosis happen. It’s no one’s fault. You didn’t do anything to “catch” cystinosis. It also means that cystinosis isn’t contagious.2 You can learn more about the genetics of cystinosis here.

What does metabolic mean? Metabolism is the chemical process by which a living organism stores and uses energy in order to stay alive.3

On a basic level, cystinosis prevents a normal cell process from occurring.2,4

  • When cells function normally, the amino acid called cystine is continuously flushed from cells.
  • In a person with cystinosis, cystine builds up to toxic levels, which can be dangerous to every cell and organ in the body, especially the kidneys and eyes.

Cystinosis: The disease in detail

Cystinosis is characterized by the continuous accumulation of a particular amino acid—cystine—in the body’s cells. Without treatment, cystine accumulation can occur in virtually all tissues and organs.5 If left untreated for too long, cystine accumulation can become toxic and may cause irreversible tissue and organ damage. Doctors and scientists do not completely understand the complex mechanisms in the body that cause accumulated cystine to do such damage to tissues and organs.2,5-8

Active treatment can make all the difference. Without treatment, the presence of excess cystine in cells all over the body leads to cell death, which is called apoptosis. Under normal circumstances, apoptosis is a healthy part of development and growth—for example, when your body sheds dead skin cells to make room for new ones. However, when excess cystine reaches toxic levels, cells die when they’re not supposed to, and normal bodily processes are affected.3,9

While the effects of cystine accumulation do not seem to be reversible, they can be prevented with long-term cystine-depleting therapy.7 Learn more on the Treatments page.

A look inside the cell

Everything that happens in the body starts in your cells. Cells are like tiny factories that create and use energy to power your muscles, nerves, organs, and everything else in your body.4

As small as they are, cells contain even smaller units (called organelles) that carry out important functions. One of those organelles is the lysosome. Think of it as a cell’s recycling center—where powerful enzymes break down proteins and other cellular matter.4

Proteins are broken down into different amino acids in the lysosome. Then specific transporters move the amino acids out of the lysosome. One of those amino acids is cystine. In a normal lysosome, cystine is transported out of the lysosome naturally.

Normal lysosome

In people with cystinosis, lysine and other amino acids are able to pass through the lysosomal membrane, but cystine is not. The transporter for cystine does not work. As a result, cystine gets trapped in the lysosome, where it builds up rapidly in just hours. The cystine forms crystals that can cause serious irreversible damage to the cells, including cell death. (This is why cystinosis is called a lysosomal storage disorder.)1,2
normal-lysosome

Cell damaged with cystinosis

Fortunately, researchers have found that by moving cystine out of the lysosome, cystine accumulation can be kept under control.2

cell-damaged

The 3 types of cystinosis

Your experience with cystinosis will be unique. Symptoms may vary in severity and the disease will progress at different rates for each person. There are three distinct types of cystinosis:

  • Nephropathic or classic infantile cystinosis is the most severe and common form of the disease, accounting for approximately 95% of cystinosis cases. “Infantile” refers to the time of onset, when symptoms typically appear, but the disease lasts a lifetime. The word “nephropathic” means it is a disease of the kidney, but if left untreated the disease can affect every cell and multiple organs.2,5
  • A person with intermediate cystinosis will start experiencing symptoms in adolescence.2,7
  • Non-nephropathic or ocular cystinosis is characterized by crystal formation in the cornea and photophobia, which is sensitivity to light. The kidney and other body systems are not affected.2,7

References

  1. Cystinosis Research Foundation. “About cystinosis.” Available at http://www.cystinosisresearch.org/About-Cystinosis/. Accessed August 20, 2015.
  2. Gahl WA, Thoene JG, Schneider JA. Cystinosis. N Engl J Med. 2002;347(2):111-121.
  3. Dictionary.com. Available at http://dictionary.reference.com/browse/metabolism. Accessed August 20, 2015.
  4. US National Library of Medicine. Genetics Home Reference. Available at http://ghr.nlm.nih.gov/handbook/basics/cell. Accessed August 20, 2015.
  5. Nesterova G, Gahl WA. Cystinosis: The evolution of a treatable disease. Pediatr Nephrol. 2013;28:51-59.
  6. Brodin-Sartorius A, Tète M-J, Niaudet P, et al. Cysteamine therapy delays the progression of nephropathic cystinosis in late adolescents and adults. Kidney Int. 2012;81:179-189.
  7. Gahl WA, Balog JZ, Kleta R. Nephropathic cystinosis in adults: Natural history and effects of oral cysteamine therapy. Ann Intern Med. 2007;147:242-250.
  8. Levtchenko EN, van Dael CM, de Graaf-Hess AC, et al. Strict cysteamine dose regimen is required to prevent nocturnal cystine accumulation in cystinosis. Pediatr Nephrol. 2006;21:110-113.
  9. Goodyer, Paul. The history of cystinosis: Lessons for clinical management. Int J Nephrol. 2011:1-7. Available at http://www.hindawi.com/journals/ijn/2011/929456/. Accessed August 20, 2015.