Disruption of the urea cycle

Urea Cycle Disorders (UCD) are inherited metabolic diseases of the liver. Originally, there are mutations in genes for enzymes of the urea cycle. Due to the malformed enzymes, ammonia can not be converted to urea and accumulates in the body. Ammonia is highly neurotoxic and can cause severe brain damage. Decisive for the expression of the disease is the affected enzyme: the earlier in the urea cycle the defective enzyme is involved, the more severe symptoms occur.

There are 8 different enzyme defects that are mainly inherited as an autosomal recessive trait. The most severe course occurs in defects of the first four enzymes. The patients are born healthy, but they quickly suffer from symptoms such as seizures, hypothermia, vomiting, brain drain, hyperventilation and lethargy, including coma, which can be fatal.

Mild forms often show symptoms only from early childhood, and these are mainly of a psychological nature. Often sufferers suffer from behavioral problems such as hyperactivity, self-aggravation, increased irritability, psychosis or hallucinations. Patients suffer from a low appetite, which subsequently leads to growth delays.

High protein consumption, stress or illness can be shuddering to a high level of ammonia in the blood and thus to lethargy and coma. The prognosis of the disease depends on the enzyme defect, on the age of onset and on the start of therapy.