- What is cystinosis?
- What is cystinosin and why do cells need it?
- What is a lysosome?
- How do people get cystinosis?
- How can cystinosis be treated? Or cured?
- What is a typical day like for someone with cystinosis?
- What is Fanconi Syndrome?
- How many people have cystinosis?
- Who is doing research on a cure for cystinosis?
Cystinosis is a rare metabolic disease characterized by an accumulation of amino acid cystine in organs and tissues, leading to severe organ dysfunction. Cystine accumlates in the cells of the body and in each and every organ because the body is unable to produce cystinosin, a critical transport protein that cleans the cystine out of the lysosome. There are three forms of cystinosis: the infantile (nephropathic) form, the intermediate (adolescent, late-onset) form; and the adult (benign) form.
Cystinosin is a specialized protein that transports cystine out of lysosomes. Cells need the protein cystinosin to control the levels of cystine in cells.
The lysosome is commonly referred to as the cell's recycling centre or the digestive system. The lysosome processes unwanted material into substances that the cell can utilize. Within the lysosome there are transporter proteins that remove matter to be used in other cellular locations. Cystinosin is a specialized transporter protein used to remove cystine from the lysosome.
Lysosomal disorders are triggered when a particular enzyme exists in too small an amount or is missing altogether. When this happens, substances accumulate in the cell. In other words, when the lysosome doesn't function normally, excess products destined for breakdown and recycling are stored in the cell.
Every person contains a gene for cystinosin, composed of two alleles(one from each parent). Cystinosis is called an autosomal recessive genetic disease. That means that both parents carry one abnormal allele (1 in 200 of us carry this abnormal allele) that leads to this condition; as such there is a 1 in 4 chance that their children will be affected by the disease. Assume that "R" is the good allele and "r" is the abnormal allele.
Cystinosis results from a gene mutation that translates into a deficiency of the membrane protein cystinosin. The gene mutation causes a biochemical malfunction that result in the abnormal accumulation of cystine inside the lysosome. This accumulation of cystine causes the cell to signal cell death. The inappropriate cell death is especially apparent in the kidneys, resulting in Fanconi syndrome.
There currently is no cure for cystinosis. Cysteamine (prounced "sis-TEE-a-meen") is the only therapy currently available for cystinosis. The brand name for cysteamine is Cystagon, so sometimes people refer to cysteamine and cystagon interchangeably.
Cysteamine is a drug that has to be taken every 6 hours to be effective. Cysteamine transforms intralysosomal cystine to cysteine, a different amino acid, which is able to leave the cell independently of the defective cystine transporter. However all the cystine still does not leave the cell, which is bad.
At a certain age, those with cystinosis may become very sensitive to light. Cysteamine eye drops are then used to help treat the cystine crystals that form in the corneas of patients with cystinosis.
Cysteamine has also demonstrated potential in clinical studies as a treatment for other metabolic and neurodegenerative diseases, including Huntington Disease and Batten Disease.
While a typical day for someone with this disorder depends on whether they are taking the treatment [some families still do not know there is a treatment, yet other suffers may experience such side effects that make taking the medication unbearable], the extent of the medication that someone may take is dependent upon their requirements a doctor's suggestions.
Generally, the Cysteamine is taken in 6 hour intervals at 6am, noon, 6pm and midnight. The other medications such as potassium Choloride, K-PHOS, Polycitra, iron and and Cysteamine eyedrops may be taken more frequently.
See below for sample medication timetable.
|6 am - Noon||1 pm - 6 pm|
** THESE SUPPLEMENTS REPLACE THE ELECTROLYTES LOST BECAUSE OF THE FANCONI SYNDROME
|7 pm - Midnight|
Fanconi Syndrome is a renal tubular disease. It causes loss of minerals and nutrients in the urine. This is a cause of rickets.
Treatment includes drinking plenty of water and replacement of salts and minerals that are lost. Therefore vitamin D and phosphate must be supplemented to replace the lost nutrients and prevent rickets to keep the bones strong.
Nephropathic cystinosis or infantile cystinosis, which is by far the most common, has been estimated to affect 1 in 100,000 or 200,000 newborns. The incidence is higher in Newfoundland Canada affecting 6 in 100,000 and in Brittany, France where 1 in 26,000 newborns are affected.
There are various parties doing research around the world to support finding a cure for cystinosis. Most of this research is funded privately.
See the research and published studies at the Cystinosis Research Foundation. This group funds quality research world wide and have researchers working in 5 countries to find a cure.