Vitamin B6 deficiency in children

Introduction to vitamin B6 deficiency in children Vitamin B6 deficiency is caused by improper food cooking or a monotonous variety. Malabsorption can also cause vitamin B6 deficiency. Vitamin B6-dependent syndrome is a structural and functional defect of an innate metabolic enzyme, kynurenine. At this time, the requirement of vitamin B6 is 5 to 10 times that required for normal children, and vitamin B6 deficiency is highly prone to occur. In infants, vitamin B6 deficiency and dependence are mainly manifested by generalized convulsions, leading to mental retardation. Also often accompanied by gastrointestinal symptoms such as vomiting, diarrhea and so on. Other manifestations include peripheral neuritis, dermatitis, and anemia. basic knowledge The proportion of illness: 0.1% - 0.3% Susceptible people: children Mode of infection: non-infectious Complications: mental retardation, stomatitis, seborrheic dermatitis, anemia

The cause of vitamin B6 deficiency in children

Effects of dietary composition (25%):

Protein metabolism requires the participation of vitamin B6. When the intake of protein in the diet is high, the amount of vitamin B6 is also high. For example, based on protein intake, 100 g of protein is ingested, and vitamin B6 is required to be taken every day. 2.5mg, suitable intake per day: 0.1-0.3mg for infants and 0.5-1.5mg for children.

Insufficient intake (20%):

Infants due to insufficient intake of vitamin B6 in the mother, resulting in decreased secretion of vitamin B6 in the milk, or artificially fed babies, milk repeatedly heated, boiled, resulting in the destruction of vitamin B6, can cause vitamin B6 deficiency in infants (vitamin B6 deficiency).

Increase in demand (20%):

Children grow faster and require more. If children suffer from tuberculosis, chickenpox, pneumonia and high fever, the consumption of vitamin B6 increases. If it is not replenished in time, it will cause a deficiency of vitamin B6. When suffering from hyperthyroidism, the vitamin B6 coenzyme activity is reduced and the vitamin B6 requirement is increased.

Drug impact (15%):

Isoniazid, cycloserine, L-dopa, hydralazine, D-penicillamine, tetracycline, etc. can all lead to vitamin B6 deficiency. Isoniazid, hydralazine and vitamin B6 form inactive derivatives, which accelerate the excretion of vitamin B6; serotonin and cycloserine are anti-metabolites of vitamin B6, which will aggravate vitamin B6 deficiency.

Absorption barrier (10%):

If you have digestive diseases, such as chronic diarrhea, intestinal infection, intestinal malabsorption syndrome and other diseases can reduce the absorption of vitamin B6.

Vitamin B6-dependent syndrome (10%):

Vitamin B6 dependence is mostly a hereditary disorder, which is a structural and functional defect of kynulinase, and its activity is only 1% of normal. Therefore, the amount of vitamin B6 required is 5 to 10 times that required for normal children, and vitamin B6 deficiency is highly prone to occur. Pregnant women take large doses of vitamin B6 during the pregnancy reaction period, so that the baby still needs to rely on a larger amount of vitamin B6 after birth.

Pathogenesis

Vitamin B6 includes six pyridoxine (PN), pyridoxamine (PM), pyridoxal (PA or PL) and their respective 5-phosphates which can be converted by enzymes. Pyridoxal 5-phosphate is an important part of this group. In decarboxylation and transamination, as a coenzyme of the enzyme system, it participates in the metabolism of amino acids, proteins, lipids, nucleic acids and glycogen in the body. If it is lacking, it can cause convulsions and peripheral nerve diseases. Therefore, vitamin B6 deficiency can cause biochemical and physiological abnormalities. Phosphorylation of PL and PM changes coenzyme, pyridoxal phosphate (PLP) and pyridoxamine phosphate (PMP). Pyridoxine is a synthetic product, also found in plants; in animals, it is often in the form of coenzyme PLP and PMP. Because pyridoxal 5-phosphate is a coenzyme of many enzymes in amino acid metabolism, protein metabolism requires the participation of vitamin B6. When vitamin B6 is deficient, it can cause decreased immunity and anemia. Vitamin B6 dependence is a concomitant recessive genetic disease affecting various vitamin B6 apoenzyme proteins and can cause convulsions, mental retardation, cystathionine, iron germ cells (iron overload) anemia, urticaria, asthma And yellow uric aciduria. In the nervous system, PLP and glutamate deaminase coenzyme protein can not be synthesized, resulting in the reduction of gamma aminobutyric acid (GABA) synthesis, GABA is a central nervous system inhibitory neurotransmitter, its brain concentration is reduced, Causes a decrease in the threshold of convulsions and clinical convulsions.

Pyridoxal 5-phosphate is an indispensable coenzyme in the first step of hemoglobin synthesis (glycine combined with succinic acid to form -aminolevulinic acid), which may be due to defects in the synthesis of -aminolevulinic acid, resulting in Hemoglobin synthesis disorders. Small cell hypochromic anemia can occur clinically.

Prevention of vitamin B6 deficiency in children

Vitamin B6 deficiency type generally has a good prognosis. It can achieve better curative effect by timely supplementing proper amount of vitamin B6. Skin damage is quickly removed. The nervous system such as peripheral neuritis is treated with high dose of pyridoxine. It can be effective and can be controlled within minutes. Convulsions. However, vitamin B6 dependence requires lifelong medication. Should be reviewed regularly to prevent recurrence, such as conscious symptoms of recurrence, should be diagnosed early.

Pediatric vitamin B6 deficiency complications Complications, low fever, seborrheic dermatitis, anemia

1. Growth retardation skeletal malformation, muscle dysplasia.

2. Digestive system: can cause glossitis, stomatitis, digestive dysfunction.

3. Nervous system: convulsions and mental retardation occur, 80% of which are associated with visual impairment.

4. Heart disease: 30% of children have heart disease similar to Marfan syndrome.

5. Infection: The immune function is reduced and infection is easy to occur.

6. Other: seborrheic dermatitis and anemia.

Pediatric vitamin B6 deficiency symptoms Common symptoms Lip dry cracks irritating irritability stomatitis nausea convulsions infants need a larger amount... Drowsiness diarrhea convulsions

1. Symptoms Although the symptoms of vitamin B6 are relatively rare, mild deficiency is more common. When the body is deficient in vitamin B6, it is often accompanied by the lack of other nutrients, especially the lack of other water-soluble vitamins, especially riboflavin, which is involved in the metabolism of vitamin B6.

(1) Growth dysplasia: Children with vitamin B6 deficiency have abnormal amino acid and protein metabolism, and their growth is retarded in infants. Anemia can also occur.

(2) Seborrheic dermatitis: Vitamin B6 deficiency can cause skin and mucous membrane inflammation, such as seborrheic and desquamative dermatitis, stomatitis, glossitis, ophthalmia, etc. Seborrheic dermatitis around the eyes, mouth and nose, and can be extended to the face, forehead, and behind the ears. It can also cause glossitis, stomatitis, and chapped lips.

(3) Neuropsychiatric symptoms: Infants less than 6 months after birth, such as lack of vitamin B6 in feeding food, can show nervousness, increased excitement and frequent systemic convulsions, leading to depression, sleepiness, mental retardation, vibration and position disappear. In infancy, the main symptoms of pyridoxine deficiency are systemic convulsions, and other manifestations of peripheral neuritis. Before the seizure, there are irritations, screams, and so on. Children within 6 months may have mental retardation due to frequent convulsions. When treating tuberculosis with isoniazid, peripheral neurodegenerative diseases (more common in adults) can occur.

(4) Digestive symptoms: often accompanied by some gastrointestinal symptoms. Such as nausea, vomiting, diarrhea and so on.

(5) Infection: Vitamin B6 also has an effect on the immune system. Lack of cell-mediated immune system damage, reduced antibody production, and prone to infection.

2. Vitamin B6 dependence is divided into the following four categories:

(1) convulsions: vitamin B6-dependent convulsions occur in babies born for hours to 3 months, repeated convulsions, anti-epileptic drug treatment is ineffective, can be relieved after intravenous injection of vitamin B6, usually with vitamin B6 5 ~ 10mg intravenous injection The maintenance dose is 10 ~ 25mg / d, the treatment of this disease needs to be maintained for life.

(2) Anemia: Vitamin B6-dependent anemia Hematology is characterized by small cell hypochromic anemia, red blood cell hyperplasia in the bone marrow, and hemoglobin deposition in the bone marrow and liver.

Peripheral neuropathy rarely occurs in anemia. Treatment with vitamin B6 0.1 ~ 1.0g / d, reticulocytes increased rapidly after 3 to 4 days.

(3) homocystinuria: children with mental retardation, skeletal deformities, muscle dysplasia, 80% of them with visual impairment, 30% of children with heart disease similar to Marfan syndrome. In some cases, large doses of vitamin B6 were given, and homocysteine disappeared, but some cases were ineffective.

(4) cystathionine: children with mental retardation, acromegaly, ear malformation, deafness, thrombocytopenia, renal diabetes insipidus, prone to kidney stones.

Pediatric vitamin B6 deficiency check

Methods for assessing vitamin B6 levels in the body include direct methods (eg, plasma pyridoxal phosphate concentration, plasma total vitamin B6 concentration, or urinary vitamin B6 concentration) and indirect methods (uric acid tryptophan degradation product levels, erythrocyte-dependent vitamin B6) Determination of enzyme activity or plasma homocysteine content).

Direct method

(1) Determination of plasma pyridoxal (PLP) concentration: plasma pyridoxal 5-phosphate is the main form of vitamin B6 in the liver and reflects the storage in tissues, but plasma pyridoxal 5-phosphate is taken against the vitamin. The response to the input is quite slow and it takes 10 days to reach a new steady state. However, various factors that may affect the concentration of PLP should be considered in the evaluation. For example, increased protein intake and increased activity of AKP can decrease plasma PLP concentration. At present, the plasma PLP concentration of 20nmol/L is used as an indicator to evaluate the nutritional status of vitamin B6. However, the concentration of 5-PLP in the fetus is very high, and it decreases rapidly in the first year after birth, and then decreases slowly. Therefore, it is difficult to evaluate the nutritional status of vitamin B6 in newborns and infants.

(2) Determination of plasma total vitamin B6 concentration (including free vitamin B6 and pyridoxine phosphate): This method is relatively simple, is a sensitive indicator to understand the nutritional status of vitamin B6 in the body, but the fluctuation of the measured value is large, thus limiting it Use value.

(3) Determination of vitamin B6 concentration in urine: Excretion of vitamin B6 in urine, especially excretion of 4-pyridinic acid, has been widely used to study the requirement of vitamin B6. The excretion of pyridoxine accounts for about 50% of the intake of vitamin B6. The discharge of 4-pyridinic acid reflects the change of dietary vitamin B6 in recent days. The amount of 4-pyruic acid excreted in normal urine is more than 0.8mg/ d, if less than 0.2 mg / d, indicating vitamin B6 deficiency.

Indirect method

(1) Level of urinary tryptophan degradation products (urine tryptophan load test): The discharge of uric acid in the urine is one of the earliest markers of vitamin B6 deficiency. Under normal circumstances, uric acid is a trace of tryptophan degradation products, the main pathway of tryptophan degradation is chymotrypsin dependent on pyridoxal 5-phosphate. Trace yellow uric acid also involves pyridoxal 5-phosphate-dependent enzymes. When vitamin B6 is deficient, the production of metabolites and derivatives of tryptophan increases and is excreted from the urine. The uric acid can reliably reflect the nutritional status of vitamin B6. The tryptophan load test can be used to confirm the diagnosis. The method is as follows: oral administration of 50-100mg/kg tryptophan solution (each total does not exceed 2g), by measuring color ammonia Acid degradation products to evaluate the nutritional status of vitamin B6, vitamin B6 deficiency in children with urine can occur a lot of jaundice, urine uric acid discharge >50mg. Normal people do not have this phenomenon, but this test may be negative in patients with vitamin B6 dependence.

(2) Determination of erythrocyte-dependent vitamin B6 enzyme activity: serum and erythrocyte aspartate aminotransferase decreased. PLP enzymes such as glutathione transaminase (EGPT), oxaloacetate transaminase (EGOT), and aspartate aminotransferase (-EAST) are required in erythrocytes, and are also sensitive indicators for evaluating the nutritional status of vitamin B6 in the body. The ratio of red blood cells plus and without PLP is often used as an indicator for evaluating the nutritional status of vitamin B6, and PLP is used to measure the activity of alanine or aspartate aminotransferase. If the activity increases by more than 20%, it indicates that vitamin B6 is deficient.

EGOT Index = EGOT + PLP / EGOT - PLP

EGPT Index = EGPT + PLP / EGPT - PLP

The EGOT activity index 1.80 is normal, and the EGPT activity index 1.25 is normal. Recently, the activity of aspartase has been measured as an index for evaluating the nutritional status of vitamin B6, but the numerical variation is large, which limits it.

(3) Plasma homocysteine content: Plasma homocysteine has recently been proposed as an indicator for evaluating the nutritional status of vitamin B6. Since the degradation of homocysteine begins with the process of transsulfuration to cysteine, it involves 5-PLP-dependent enzymes. However, recent studies have shown that folic acid and vitamin B12 are more closely related to the level of plasma homocysteine.

Check for ECG and EEG. The electroencephalogram examines waveforms with abnormal frequency and amplitude changes.

Diagnosis and identification of vitamin B6 deficiency in children

diagnosis

Diagnosis can be made by relying on medical history, clinical signs and symptoms, and laboratory tests.

1. Medical history: Carefully ask about medical history. Whether the child has insufficient intake, partial eclipse, anorexia; whether it is reasonable diet, whether the proportion of each nutrient is reasonable; whether there are diseases that hinder absorption and utilization, such as chronic depletion diseases, gastrointestinal diseases and other diseases that affect absorption; There are factors that increase the amount of demand, such as faster growth and development, fever, etc.; recently whether to take drugs that affect the activity of vitamin B6.

2. Clinical manifestations: In case of unexplained convulsions, anemia or chronic diarrhea in infancy, if hypocalcemia, hypoglycemia, hyponatremia and infectious diseases have been ruled out, vitamin B6 deficiency or dependence should be considered. Infants have growth and developmental dysfunction, convulsions, convulsions and other nervous system manifestations, such as peripheral neuritis, dermatitis, oral, nasal seborrheic dermatitis and anemia.

3. Therapeutic response: After the injection of vitamin B6 100mg, convulsions can be used as a basis for diagnosis.

4. Vitamin B6 dependence: There is no history of vitamin B6 deficiency in the diet, and the use of common antispasmodic agents for seizures is ineffective, and the administration of large doses of vitamin B6 can control the onset of seizures. At the same time, after the withdrawal, the seizures often recur within a few days. Conducive to the diagnosis of vitamin B6 dependence.

5. Laboratory tests: by measuring plasma pyridoxal phosphate (PLP) concentration, plasma total vitamin B6 concentration, urine vitamin B6 concentration, urine tryptophan degradation products, erythrocyte-dependent vitamin B6 enzyme Methods such as activity and plasma homocysteine help diagnose.

Differential diagnosis

1. Anemia: Identification of anemia caused by other causes. For example, iron deficiency anemia, and thalassemia.

2. Developmental disorders: identification of developmental disorders and skeletal deformities caused by other causes.

3. The identification of convulsions and mental retardation caused by convulsions, mental retardation and other causes.

4. Digestive symptoms: often accompanied by some gastrointestinal symptoms. Such as nausea, vomiting, diarrhea and so on. Pay attention to the identification of gastroenteritis.

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