mucopolysaccharidosis type Ⅲ
Introduction
Introduction to mucopolysaccharidosis type III Mucopolysaccharidosis type III, also known as Sanfilippo syndrome, is an autosomal recessive hereditary disease. The clinical features and biochemical abnormalities of this type are different from those of type I and II, which are characterized by severe reaction. However, the lesions around the body are relatively mild. The difference with the type I is that the appearance is not like the disease, the gnome is not obvious, and there are no complications such as corneal opacity or heart disease. Mild contracture of the elbow and knee joint, even if there is hepatosplenomegaly, it is very mild. basic knowledge The proportion of illness: 0.001% Susceptible people: no special people Mode of infection: non-infectious complication:
Cause
Mucopolysaccharidosis type III cause
(1) Causes of the disease
The disease is caused by autosomal recessive inheritance.
(two) pathogenesis
According to the mixed culture results of fibroblasts, the disease can be divided into four types A, B, C, D, type A is caused by the lack of lysosomal heparan-N-sulfatase; type B is due to N-acetyl- -D-glucosaminidase (Fig. 1); type C is due to acetyl CoA--glucosamine-N-acetyltransferase deficiency; type D is due to N-acetyl--D-glucosaminide- 6-sulfate enzyme deficiency caused by the lack of the above enzymes, the heparan sulfate can not be gradually degraded, but stored in the liver and tissues, and a large amount of urine excretion, although the enzyme defects are different, but the symptoms of type 4 are completely the same, clinically It is indistinguishable that type 4 cells can correct each other's metabolic defects and correct the mucopolysaccharide deposition in the cells of type 4 patients. This "cross-correction" phenomenon is probably because the fibroblasts of different types of patients can supply each other with a lack of enzymes. Caused.
Pathology: pathological examination showed that large vacuoles were formed in hepatocytes and Kupffer cells as well as rectal mucosal cells, the ventricles were enlarged, and the brain parenchymal neurons were severely degenerated and lost, while the residual neuron balloon-like changes contained lipids and appearance. Swelling; a large increase in sphingolipids in the brain, swelling and swelling of the basal ganglia and optic ganglion cells, and these lesions in the brain are the cause of severe clinical mental retardation.
Electron microscopy showed different types of cytoplasmic inclusions; it had uniform particulate matter and small concentric membrane small vacuoles, with hydrophilic outer membrane and zebra body vacuoles.
Histochemical examination showed that the mucopolysaccharides deposited in the brain, liver and kidney were mainly heparan sulfate, and there were glycolipids in the brain tissue, and the GM ganglioside content increased.
Prevention
Mucopolysaccharidosis type III prevention
Glycogen accumulation disease is a group of children with disorders of hereditary glycogen metabolism. It is characterized by excessive accumulation of glycogen in the body tissue and difficulty in decomposition. It is rarely a metabolic disorder of glycogen, resulting in less glycogen storage in the body. The original cumulative disease is not a disease, but a group of diseases. There are 12 kinds of diseases currently identified. The clinical features are characterized by hypoglycemia. The organs involved are mainly liver, kidney and skeletal muscles. Chromosomal recessive inheritance, no gender differences, mostly in childhood, some patients to adults, the disease no longer develops, can maintain general health.
The patients are mainly due to the lack of certain enzymes that break down glycogen, such as glucose-6-phosphatase, -1,4 glucose chymase, phosphofructokinase, hepatic phosphorylation kinase and the like.
Parents of many patients marry close relatives, avoiding close relatives marriage is an important part of preventing this disease. Once glycogen accumulation is found, it is mainly to prevent and treat hypoglycemia, a small amount of meals, limit fat and total calories, limit physical activity, serum lactic acid The highest, should take sodium bicarbonate to prevent acidosis, corticosteroids, adrenaline, glucagon, etc. can help control hypoglycemia.
Complication
Mucopolysaccharidosis type III complications Complication
The disease can be complicated by spastic quadriplegia, aggressive behavior, etc., even if there is hepatosplenomegaly, it is very mild.
Symptom
Mucopolysaccharidosis type III symptoms Common symptoms Ventilatory deafness, weakness, joint stiffness, mental retardation, splenomegaly
Progressive mental retardation is the most prominent feature of this disease. The mental development is normal or only slightly backward after 1 year of life. The mental retardation usually occurs in 4 to 7 years old. It is very serious at the age of 10 and progresses in mental retardation. At the same time of exacerbation, progressive neurological symptoms such as convulsions, excessive exercise, paralyzed quadriplegia, general weakness, aggressive behavior, etc. may occur, which is the most prominent symptom of the disease.
The body changes lightly or normally. Only 1/4 of the patients have short stature. Most patients have normal facial performance. A few patients have large heads, ugly face, abdominal distension, progressive deafness, joint stiffness and hand flexion. Skeletal changes only have multiple osteogenesis imperfecta and dense posterior parietal thickening. These changes have a certain degree of specificity for the diagnosis of the disease. Liver and splenomegaly are mild to moderate, no corneal opacity, no heart involvement. .
Examine
Mucopolysaccharide storage disease type III examination
The large amount of mucopolysaccharide excreted in the urine is heparan sulfate. The activity of the enzyme in the serum of MPSIII-B patients is 2% to 16% of the normal, while the enzyme activity of heterozygotes is less than 35% of the normal, lymphocytes in the blood. Metachromatic inclusion bodies can be found in neutrophils and bone marrow cells.
X-ray examination: X-ray findings are similar to mucopolysaccharidosis type I and II. About half of patients may have type I changes, but to a lesser extent, only 1/4 of them develop pygmy, and the other half may have long bones and The ribs are enlarged and deformed. In some patients, the lumbar vertebral body is biconvex, and the density of the posterior part of the parietal bone is increased and thickened.
Diagnosis
Diagnosis and identification of mucopolysaccharidosis type III
According to clinical features and urine analysis results, the diagnosis of this type of syndrome should be suspected, and the diagnosis must rely on the confirmation of specific enzyme defects, because the four subtypes of this type have similar clinical manifestations.
The precautions for differential diagnosis are the same as those for mucopolysaccharidosis.
