What is tyrosinemia caused by?

summary

Also known as "congenital tyrosine blood (disease)". It is an autosomal recessive clinical syndrome with abnormal tyrosine metabolism, severe liver injury and renal tubular defects caused by the lack of fumaracetate hydrolase. Acute patients have hepatomegaly, fatty infiltration or necrosis of hepatocytes. Chronic patients may have liver fibrosis, cirrhosis, and even liver cancer. The kidney may have tubular degeneration, islet hyperplasia and degeneration of basal ganglia. Clinically, acute and chronic patients can occur in the same family. Acute type is often infant, vomiting, hepatosplenomegaly, edema, ascites, shortness of breath and bleeding tendency, some jaundice, 90% of rapid death. Chronic type usually occurs in infants after 6 months, with cirrhosis, hyperphosphatemia, hypophosphatemia and chondropathy. Examination may have high amino acids, such as tyrosine, proline, threonine and phenylalanine, abnormal liver function, hypoglycemia, low serum protein and bleeding tendency. Limit phenylalanine and tyrosine diet, correct hypoglycemia, hypokalemia, alkalosis and bleeding tendency. Kidney disease should be controlled. The only effective treatment is early liver transplantation. What causes tyrosinemia?

What is tyrosinemia caused by?

1. The deficiency of some enzymes and the absorption of amino acids. For example, phenylketonuria is caused by phenylalanine hydroxylase deficiency; Branched amino acids α- The deficiency or decrease of ketoacid decarboxylase caused maple syrupurine disease; Isovalerinemia caused by deficiency of isovaleryl CoA dehydrogenase; Homocystinuria caused by cystathionine synthase deficiency; Argininemia caused by arginase deficiency; Lysine ketoglutarate reductase deficiency causes hyperlysinemia and so on.

2. The latter is caused by the reversal of amino acids and the absorption of amino acids, which is often caused by the absorption of certain amino acids in the intestine or other tissues, such as liver brain kidney syndrome, hartup disease, etc. Hereditary tyrosinemia is an autosomal recessive inheritance, which is caused by the defect of the gene encoding fumaracetoacetate hydrolase on chromosome 15, resulting in tyrosinemia and accumulation of metabolites.

3. Hartup disease is caused by the deficiency of neutral amino acid transporter. The pathogenic gene of the protein is located on chromosome 2. The female carries the pathogenic gene to the offspring. Due to the transport of tryptophan through renal tubules, the excretion of these amino acids in urine and feces increases. There is a large amount of urine blue mother (indican) excretion, mainly indolyl sulfate. Especially after eating food containing a large amount of L-tryptophan, there are also a large number of abnormal non hydroxylated indole metabolites in urine. Because a large amount of tryptophan is excreted in urine and lost, the synthesis of nicotinic acid as raw material is reduced, leading to tyrosinemia.

matters needing attention

At present, diet therapy alone is not recommended for the treatment of tyrosinemia. However, as the plasma tyrosine level may be increased, eye and skin lesions may occur, and even brain development may be affected, patients need to be combined with diet therapy of low tyrosine and phenylalanine while receiving the treatment of niticillin. Generally, the total protein intake of children under 2 years old is 3 g / (kg · day), which gradually decreases to 2 g / (kg · day) with the increase of age. The intake of natural protein is controlled within 2 g / (kg · day) in infancy and reduced to 1 g / (kg · day) in childhood. The rest of the protein is provided by formula nutritional powder without tyrosine and phenylalanine; In addition, a certain amount of vitamins and minerals should be given, plasma tyrosine concentration should be monitored regularly, and diet treatment should be adjusted timely