Tyrosinemia is caused by a lack of the enzyme needed to metabolize the amino acid tyrosine.
Symptoms include intellectual disability, liver and kidney disease, and body fluids that smell like boiled cabbage.
The diagnosis is based on a blood test.
A special diet and sometimes drugs may help some children.
Amino acids are the building blocks of proteins and have many functions in the body. Children with tyrosinemia are unable to completely break down (metabolize) the amino acid tyrosine. By-products of this amino acid build up, causing a variety of symptoms. These by-products also cause body fluids, such as urine and sweat, to smell like boiled cabbage.
There are different types of inherited disorders. In tyrosinemia, both parents of the affected child carry a copy of the abnormal gene. Because usually two copies of the abnormal gene are necessary for the disorder to occur, usually neither parent has the disorder. (See also Overview of Hereditary Metabolic Disorders.)
In some states, the disorder is detected with newborn screening tests.
There are two main types of tyrosinemia and a third, uncommon form:
Type I tyrosinemia is most common among children of French-Canadian or Scandinavian descent.
Newborns may have liver failure. Older infants and children have dysfunction of the liver, kidneys, and nerves, resulting in irritability, rickets, or even liver failure and death.
Every state in the United States requires all newborns be screened for type I tyrosinemia with a blood test. To confirm the diagnosis, genetic testing or other tests of the blood and urine and a biopsy of the liver are done.
Restriction of the amino acids tyrosine and phenylalanine in the diet is recommended. A drug called nitisinone (also known as NTBC), which blocks production of toxic metabolites, may help children with type I tyrosinemia. Often, children with type I tyrosinemia require a liver transplant.
Type II tyrosinemia is less common. Affected children sometimes have intellectual disability and frequently develop sores on the skin and eyes.
Diagnosis of type II tyrosinemia is with a blood test. Other tests of the blood and urine and a biopsy of the liver may be done.
Treatment of type II tyrosinemia is by restricting tyrosine and phenylalanine in the diet.
Type III tyrosinemia is very rare. Mild intellectual disability, seizures, and periodic loss of balance and coordination are the most common symptoms.
Diagnosis of type III tyrosinemia is with a newborn blood screening test. Urine and blood tests may also be done if the screening is abnormal.
Treatment of type III tyrosinemia is by restricting tyrosine and phenylalanine in the diet.