In this group of six diseases (frequency: 1 : 8,500), ammonia detoxification is impaired. Ammonia is a toxic substance that is normally converted to urea in the liver and excreted in the urine.
In affected individuals, ammonia accumulates in the blood and leads primarily to brain impairment manifested by seizures, neurological symptoms, mental developmental delay and impaired consciousness. Treatment is difficult and includes a lifelong low-protein, high-calorie, high-carbohydrate diet and various medications.
Transport disorders
In cystinuria (not to be confused with cystinosis!), certain amino acids, particularly cystine, cannot pass through the cells of the small intestine and urinary tubules. This inherited disease occurs in one in 10,000 children. The most important and usually the only symptom is recurrent kidney stones, as the corresponding amino acids accumulate in the urine and thus precipitate.
Often, high fluid intake, which greatly dilutes the urine, is sufficient for treatment; otherwise, medications may be given.
