Gradual decline in intelligence after half a year or 1 year old
Introduction
Introduction The amino acid metabolism disease is amino acidopathy, or amino aciduria. Can be divided into two categories: one is the enzyme defect, which makes the amino acid catabolism block, and the other is the defect of the amino acid absorption transport system. At least half of the 48 genetic amino acid diseases listed by Rosenberg and Scriver have significant neurological abnormalities, and the other 20 amino acid diseases cause defects in the kidney transport of amino acids, which can cause secondary nervous system damage. Like other hereditary metabolic diseases, amino acid disease does not affect the intrauterine growth, development or childbirth of the fetus, and there is no sign in the early stage. The main clinical features are normal appearance and activity at birth. After half a year or 1 year old, there is a gradual emergence of intelligent decline. After appropriate treatments such as amino acid supplementation, diet control, and vitamins, neurological symptoms can be improved in many cases.
Cause
Cause
(1) Causes of the disease
Except in a few cases, amino acid metabolic diseases are autosomal recessive genetic diseases, and the offspring of close relatives are more common.
(two) pathogenesis
There are two main causes of amino acid metabolic diseases, namely, the lack of certain enzymes and the malabsorption of amino acids. The former is known to be an enzyme or a certain lack or decrease of certain enzyme activity, such as the lack of phenylalanine hydroxylase causing phenylketonuria; the lack or decrease of branched amino acid -ketoacid decarboxylase causes maple Marile syrup urine disease; isovalerate caused by lack of isovaleryl-CoA dehydrogenase; homocysteine caused by cystathionine synthetase deficiency; sperm caused by arginase deficiency Lysemia; high lysineemia caused by lysine ketoglutarate reductase deficiency and the like. The latter is caused by the reverse of amino acid and malabsorption, and is often a barrier to the absorption of certain amino acids by the intestines or other tissues, such as liver-brain-kidney (Lowe) syndrome, Hartnup's disease, and the like.
1. Hereditary tyrosinemia (hereditary tyrosinemia) is autosomal recessive, which encodes a defect in the gene of fumarylacetoacetate hydrolase on chromosome 15, resulting in the accumulation of tyrosine and metabolites.
2. Hartnup disease is caused by a defect in the transporter of neutral amino acids (such as mono- and mono-amino acids). The causative gene of this protein is located on chromosome 2, and the female carries the disease-causing gene to the offspring. Due to the transport of tryptophan through the renal tubules, the excretion of these amino acids in urine and feces increases, and there is a large amount of urinary blue in the urine, mainly indoxyl sulfate, especially in eating a large amount. After L-tryptophan food, the urine also contains a large number of abnormal metabolites of non-hydroxylated hydrazine. Loss of a large amount of tryptophan through the urine discharge reduces the synthesis of niacin as a synthetic raw material, resulting in a change in the skin of the pellagra. The pathological basis of the disease has not been determined.
Examine
an examination
Related inspection
Cerebrospinal fluid amino acid nervous system examination
At present, there are more than 100 genetic diseases caused by amino acid metabolism disorders. With the continuous advancement of biochemical detection technology, new discoveries will continue to increase. Amino acid metabolism can often lead to nervous system dysfunction. When the nervous system is involved, usually only mild mental motor developmental delay occurs, and there are obvious symptoms until 2 to 3 years after the onset of the disease.
Like other hereditary metabolic diseases, amino acid disease does not affect the intrauterine growth, development or childbirth of the fetus, and there is no sign in the early stage. The main clinical features are normal appearance and activity at birth. After half a year or 1 year old, there is a gradual emergence of intelligent decline. After appropriate treatments such as amino acid supplementation, diet control, and vitamins, neurological symptoms can be improved in many cases.
1. Hereditary tyrosinemia or Richner-Hanhart disease is a rare dermatic amino acidopathy. The clinical manifestations are as follows:
(1) About half of the children have mild to moderate mental decline, and may have self-discipline behavior and uncoordinated performance of limb movements, and language defects are more prominent. Corneal erosion often causes tearing, photophobia, and redness of the eyes at 1 year of age or at the age of 1 year, and neovascularization and corneal opacity occur. The palm and plantar keratinization is associated with hyperhidrosis and pain. It is an inflammatory reaction nodule caused by crystalline tyrosine deposition and is also the cause of corneal lesions.
(2) may have liver, splenomegaly or cirrhosis, ascites and other liver failure, often died after 1 or years of illness. Neonatal tyrosinemia can cause liver failure and death. Increased levels of blood tyrosine and urinary tyrosine are diagnostic, and amino acids such as blood methionine (methionine) can also be increased.
2. Hartnup disease is a relatively common tryptophan transport disorder amino acid disease, named after the first family of diseases, the incidence rate is 1 / 24,000 live infants.
The clinical manifestations are as follows:
(1) The child is normal at birth, and the symptoms appear in the late stage of the baby or early childhood. The characteristic clinical manifestation is intermittent red scaly rash, covering the face, neck, hands and feet, which is similar to the lesion of pellagra.
(2) may have growth retardation, episodic personality disorder such as emotional changes, can not control temper, mental disorder - hallucinatory psychosis, paroxysmal cerebellar ataxia (gait instability, intentional tremor and dysarthria, etc. ), occasionally there may be signs such as tendon, dizziness, nystagmus, diplopia and ptosis.
(3) Sun exposure, emotional stress response and taking sulfa drugs can trigger symptoms, and the attack lasts for about 2 weeks, followed by a relatively normal period of time. As the child matures, the frequency of seizures gradually decreases, and some children may have a mild persistent mental decline.
Diagnosis
Differential diagnosis
It is mainly based on the typical clinical manifestations of different types of amino acid metabolic diseases, as well as laboratory tests to make a diagnosis. Genetic testing has the significance of diagnosis and differentiation.
