Pyrimidine 5'-nucleotide deficiency
Introduction
Introduction to pyrimidine 5'-nucleotide deficiency Pyrimidine 5'-nucleotide deficiency (P5'ND) erythrocyte pyrimidine 5'-nucleotidase deficiency is an autosomal recessive enzyme that is associated with RNA catabolism. It is the most common enzyme deficiency disease in nucleotide metabolism abnormalities. basic knowledge The proportion of illness: 0.002% Susceptible people: no special people Mode of transmission: mother-to-child transmission Complications: galactosemia Hepatolenticular degeneration Vitamin D deficiency rickets
Cause
Pyrimidine 5'-nucleotide deficiency etiology
(1) Causes of the disease
Autosomal recessive inheritance.
(two) pathogenesis
P5'N is a zinc (Zn)-dependent metalloenzyme that is activated by Cr2, Zn2, and Mg2, while Hg2 and Pb2 significantly inhibit its activity. As the red blood cells mature and senescence, the P5'N content gradually decreases, and P5'N exists. Type I and II, which are encoded by different genes, are present in brain tissue in addition to red blood cells.
Ribosomal RNA degrades into 5'-nucleotides in normal reticulocytes, and its non-dispersible metabolites (cytidine, thymidine, and uridine monophosphate) are rephosphorylated by P5'N to form dispersible products. Through the cells, P5'N-deficient reticulocytes aggregate a large number of cytidine and uridine complexes, which can make the total nucleotide pool more than 5 times larger than normal red blood cells. Because ribosomes can not degrade normally in defective cells, Thus, a large amount of aggregation forms the basophilic spotting particles in the Reiter staining, and P5'N deficiency is previously classified as "high ATP syndrome" due to the large consumption of adenosine monophosphate instead of pyrimidine in the defective red blood cells.
The mechanism of hemolytic activity of P5'N deficiency is: pyrimidine nucleotide accumulation in the severe deficiency of P5'N in red blood cells, competitive inhibition of ATPase and ATP production related enzymes, competitive inhibition with 6-phosphogluconate and non-NADP Competitive inhibition of G-6-PD, in addition to the accumulation of acidic pyrimidine nucleotides, the pH of the red blood cells decreased, further reducing the activity of G-6-PD and 6PGD, affecting the pentose phosphate bypass activity, both of which interfere ATP is produced, which shortens the life span of red blood cells and appears as chronic non-spherical erythrocyte hemolytic anemia.
Prevention
Pyrimidine 5'-nucleotide deficiency prevention
Attention should be paid to prevention, eugenics, pre-marital and prenatal examinations.
Complication
Pyrimidine 5'-nucleotide deficiency complications Complications galactosemia hepatolenticular degeneration vitamin D deficiency rickets
1, galactosemia: from the beginning of the newborn do not feed milk and galactose-containing foods, such as soy milk, sugar, etc., substituted for cereals, fruits, meat, eggs and food.
2, phenylketonuria: from 2 months after birth, given a low phenylpyruvate diet, replaced by hydrolyzed protein, until about 6 years old.
3, hepatolenticular degeneration: must limit the copper-containing diet. Medication: Supplement the lack of enzymes, coenzymes or metabolites to remove excess material.
4, anti-vitamin D rickets, given vitamin D treatment, and regular check to observe the effect.
Symptom
Pyrimidine 5'-nucleotide deficiency symptoms Common symptoms Intelligence reduces hemolytic anemia
1. Lifetime hemolytic anemia Anemia is often mild to moderate, which can be aggravated by infection, stress and pregnancy.
2. Splenomegaly and intermittent jaundice.
3. P5'N deficiency caused by mental development in low brain tissue.
Examine
Examination of pyrimidine 5'-nucleotide deficiency
P5'N deficiency heterozygous blood picture is normal, homozygous or compound heterozygous P5'N activity is only 5% to 10% of normal, there is lifelong hemolytic anemia with splenomegaly and intermittent jaundice, infection, stress and pregnancy Anemia can be aggravated, and some patients can also have developmental delays.
1. Peripheral blood hemoglobin concentration is 80-100g/L, reticulocyte is about 10%; basophilic red blood cells are persistent, ranging from 4% to 5% (normal <3%), suggesting the diagnosis of this disease.
2. The autolysis test is positive and the glucose is poorly corrected.
3. Screening for elevated cytosine nucleotides.
4. P5'N activity quantitative test: diagnosis of this disease depends on this test, the normal range of P5'N activity: adult 12.10 ± 2.52; neonatal 19.18 ± 3.62 (inorganic phosphorus method); P5 'N activity of this disease is lower than normal .
Diagnosis
Diagnosis and identification of pyrimidine 5'-nucleotide deficiency
According to family history, clinical manifestations and determination of erythrocyte P5'N activity were confirmed.
