Symptoms & Effects
There are three clinical forms of cystinosis: Infantile (nephropathic) cystinosis; late-onset cystinosis; and benign cystinosis. Infantile cystinosis is the most severe and the most common type of cystinosis. Children with nephropathic cystinosis appear normal at birth, but by 9-10 months of age have symptoms that include excessive thirst and urination and failure to thrive. Children often appear pale and thin and have short stature. The abnormally high loss of phosphorous in the urine leads to rickets.
After one year of age, cystine crystals appear in the cornea and cause a severe sensitivity to light (photophobia). Children with cystinosis also have an increased level of cystine in their white blood cells. In time, patients can develop problems such as hypothyroidism, severe muscle weakness and central nervous system complications. These children have normal intelligence, but have an unusual defect in short-term visual memory. Many have poor GI motility. Cystagon™ causes hyper secretion of gastric acid, resulting in gastric distress.
Effects of Cystinosis
Over a period of years, the cystine damages various organs including the kidneys, liver, muscles, white blood cells, eyes and central nervous system. The cystine crystallizes in cells throughout the body, slowly destroying the organs. The earliest abnormalities are seen in the kidney. Cystinosis is a common cause of the Fanconi syndrome, a renal tubular disease. By about one year of age, patients have very large volumes of urine and lose large amounts of salt and other minerals in their urine.
Without specific treatment, these children progress to end-stage renal failure by an average age of nine years. In the past, this meant death. Now these patients can receive renal dialysis or renal transplantation. However, even with successful renal transplantation, these children go on to develop abnormalities in other organs.
Fortunately, the drug cysteamine slows the progression of cystinosis by removing the cystine from the cells. In order for the drug treatment to be effective, it must be taken every six hours. Although this has led to a much better future for these children, cysteamine is not a cure.