CYSTINOSIS

Genetic information and gene affected
Cystinosis is a rare genetic metabolic disease that causes cystine, an amino acid, to accumulate in lysosomes of various organs of the body such as the kidneys, liver, eyes, muscles, pancreas, brain, and white blood cells. Although cystinosis primarily affects children, a form of the disease also occurs in adults. In cystinosis, the cystine content of cells increases to an average of 50 to 100 times its normal value. This increase is caused by an abnormality in the transport of cystine out of a sac-like compartment of the cell called the lysosome. Because of cystine's low solubility in water, this amino acid forms crystals that accumulate within the lysosomes of cells. The accumulation of cystine is believed to destroy the cells. The chromosome location gene is located on the short (p) arm of chromosome 17 at position 13.
Diagnosis
Cystinosis may be diagnosed prenatally by examining cystine levels in chorionic villi (obtained by chorionic villus sampling, usually done at 10–12 weeks gestation). Chorionic villus sampling is tissue sample of tiny pieces of placental tissue obtained by inserting a thin needle or narrow tube into the uterus and is performed at 10–12 weeks of gestation. The values in a fetus with cystinosis are more than 10 times greater than normal. It also can be diagnosis by amniocentesis, cells contained in amniotic fluid usually done at 16–18 weeks gestation. Amniocentesis (sample of amniotic fluid obtained by inserting a thin needle into the uterus) can be performed at 16–18 weeks of gestation. In early infancy, cystinosis is usually diagnosed by measuring free cystine in white blood cells and skin fibroblasts.
Treatment and management
Cystinosis is treated by a variety of pharmacologic and nonpharmacologic therapies as well as by surgical transplantation. Pharmacologic therapy, the aim of specific treatment for cystinosis is to reduce cystine accumulation within the cells. This goal is achieved by cysteamine treatment, which has proven effective in delaying or preventing renal failure. Cysteamine treatment also improves growth in children with cystinosis. The growth improvement with cysteamine bitartrate usually allows the patient to maintain growth along a percentile but does not usually aid in achieving "catch-up" growth. Organ transplantation, Kidney transplantation has proven useful in patients with cystinosis. If a patient with cystinosis receives a kidney transplant and reaches adulthood, the new kidney will not be affected by the disease. However, without cysteamine treatment, kidney transplant recipients can develop complications in other organs due to the continued cystine accumulation in the body. These complications can include muscle wasting, difficulty swallowing, diabetes, hypothyroidism, and blindness. Not all older patients, however, develop these symptoms. In both young children with cystinosis and older patients with a kidney transplant, cysteamine eye drops may be useful in removing the corneal cystine crystals and reduce photophobia. However, as of early 2001, the drops have not yet received FDA approval.
Signs and symptoms
Although the symptoms of cystinosis vary, depending on the type of disease present, general symptoms include: * acidosis * dehydration * rickets * growth retardation * renal glomerular failure * corneal ulcerations and retinal blindness * delayed puberty * swallowing difficulties
Definition
* Acidosis is a condition in which there is excessive acid in the body fluids. It is the opposite of alkalosis (a condition in which there is excessive base in the body fluids). * Dehydration means your body does not have as much water and fluids as it should. * Rickets is a disorder caused by a lack of vitamin D, calcium, or phosphate. It leads to softening and weakening of the bones. * Growth retardation Delayed growth is poor or abnormally slow height or weight gains in a child younger than age 5. * A corneal ulcer is an erosion or open sore in the outer layer of the cornea. It is associated with infection. * Blindness is a lack of vision *
Since 1980, the prognosis of a child with cystinosis has greatly improved. However, if children with the disease receive no treatment, they rarely survive past the age of nine or ten.