Hypophosphatase in children

Introduction to Pediatric Phosphatase Hypophosphatasia is a rare autosomal recessive hereditary disease, and a few are dominant inheritance. It occurs mostly in children. It is characterized by low or absent alkaline phosphatase activity in tissues such as blood, liver, bones and kidneys. Incomplete ossification, easy fracture and increased phosphorylamine alcohol secretion in urine. basic knowledge The proportion of illness: 0.001% Susceptible people: children Mode of infection: non-infectious Complications: hypercalcemia, kidney damage

Pediatric phosphatase hypoxia

(1) Causes of the disease

The disease is mostly autosomal recessive hereditary disease, a few dominant inheritance, the cause is not completely clear, it seems that due to insufficient alkaline phosphatase in the body or dysfunction of osteoblasts and chondrocytes, the resulting cartilage matrix and bone-like tissue Poor performance, reduced formation of alkaline phosphatase, calcium salt can not be properly deposited.

(two) pathogenesis

The bone tissue in the bone tissue is accumulated in a large amount, the calcium salt can not be normal, the trabecular bone is irregularly arranged, the osteogenesis is reduced, and the calcium salt cannot participate in the normal ossification, and the secondary hypercalcemia and urinary calcium displacement increase. Kidney damage occurs during infancy, manifested as mild interstitial fibrosis of the kidney, glomerular atrophy or calcium deposits in the renal tubules and surrounding tissues, resulting in renal insufficiency, and early healing of the cranial suture due to hypercalcemia Due to poor dentin structure and poor attachment of periodontal ligament, tooth dysplasia, common deciduous teeth.

Pediatric phosphatase deficiency prevention

Precautions should be taken from pre-pregnancy to prenatal.

Pre-marital medical examination plays an active role in preventing birth defects. The size of the effect depends on the examination items and contents, including serological examination (such as hepatitis B virus, treponema pallidum, HIV) and reproductive system examination (such as screening for cervical inflammation). General medical examinations (such as blood pressure, electrocardiogram) and asking about the family history of the disease, personal medical history, etc., do a good job in genetic disease counseling.

Pregnant women should avoid harmful factors as far as possible, including away from smoke, alcohol, drugs, radiation, pesticides, noise, volatile harmful gases, toxic and harmful heavy metals, etc. In the process of antenatal care during pregnancy, systematic screening of birth defects is required, including Regular ultrasound examination, serological screening, etc., if necessary, a chromosome examination.

Once an abnormal result occurs, it is necessary to determine whether to terminate the pregnancy; the safety of the fetus in the uterus; whether there is sequelae after birth, whether it can be treated, how to prognose, etc., and take practical measures for diagnosis and treatment.

Pediatric phosphatase hypoxia complications Complications, hypercalcemia, kidney damage

Secondary hypercalcemia, kidney damage, renal insufficiency, polydipsia, early healing of the cranial suture, often secondary to increased intracranial pressure or neurological symptoms, a small number of joints, tendons and intervertebral ligaments Peripheral calcification, short limbs, curved deformities and fractures, due to thoracic deformity, weakness and difficulty breathing, prone to death.

Symptoms of phosphatase hypoxia in children Common symptoms Inability to grow slowly Drinking gait instability Anorexia softening polyuria Thoracic deformity Hypercalcemia Proteinuria

According to the early onset of clinical symptoms, it is divided into neonatal type (congenital lethal hypophosphatasia), infant type, child type and juvenile type (hypophosphatasia tarda), but these types are not completely demarcated, often repaired and The continuation of the improvement process, the neonatal type has softening of the skull after birth, short limbs, curved deformities and fractures, often accompanied by annular deep concave incisions on the surface of the limbs. In some cases, blue sclera, convulsions, cyanosis, etc. can be seen. Symptoms, severe cases are stillbirth at birth, due to weakness of the thorax and difficulty breathing, the infant type often occurs 1 to 6 months after birth, manifested as weight loss, slow growth and slow growth of the head circumference, skull Softening, widening of the cranial suture, prominent scrotal, scalp vein engorgement, thoracic deformity and limb flexion.

When hypercalcemia and renal dysfunction occur, there may be anorexia, vomiting, constipation, fever, polydipsia, low muscle tone, convulsions, proteinuria or pyuria. Some children may see skin pigmentation, when the lesions naturally improve, After the age of 2, children with symptoms such as walking late, gait instability, limb pain, bending deformity, tooth dysplasia, etc., dental caries and deciduous teeth are common, due to craniosynostosis, often occur Increased intracranial pressure or neurological symptoms, the older the onset, the more atypical the clinical symptoms, the milder the lesions, the adult type often only complains of bone pain, the fractures and the bone deformities left by the lesions in childhood. A small number of patients develop calcification around the joints, tendons and intervertebral ligaments. Individuals only show early deciduous teeth and bone lesions are not obvious.

Pediatric phosphatase hypoxia check

In serum, bone, liver, kidney, pancreas, intestinal mucosa, lung, meninges and brain parenchyma, and white blood cells, alkaline phosphatase activity is significantly reduced or disappeared, and patients and heterozygous carriers have a large number of blood and urine. Phosphoethanolamine (PEA), foreign data reported, urine and plasma PEA normal values were 17 ~ 99mol / dl, 0.21 ~ 0.33mol / dl, normal PEA clearance rate of 4 ~ 12ml / min, miscellaneous The urinary PEA of zygote carriers is 3-8 times of the normal value; the plasma concentration is about 2 times; the renal PEA clearance rate is 4 times of the normal value, and the urine PEA of patients with hypophosphatase is 10 to 50 times of the normal value, plasma PEA is twice as large as heterozygotes (0.75-0.85mol/dl), blood calcium is often elevated, high urinary calcium, renal function damage, proteinuria or pyuria may occur, and blood non-protein nitrogen is increased.

X-ray examination: The bone manifestations of mild cases are similar to those of severe rickets. In severe cases, the skeletal dysplasia of the whole body bones, the long bones of the long bones are jagged and uneven, the ossification is uneven, the common ossified translucent area, the backbone is curved into Horns, even more, some bones are not ossified at all. In infanthood, the skull is thin, ossification is incomplete or only irregular ossification centers are seen, cranial sutures and cardia are widened, lesions can be repaired in childhood, re-ossification or Remnant bone deformities and fractures, X-ray signs of narrow head and increased intracranial pressure may occur due to craniosynostosis, and osteoporosis or fracture is common in adulthood, and sometimes kidney stones appear.

Diagnosis and diagnosis of phosphatase deficiency in children

Clinical manifestations, blood, urine biochemical examination and X-ray photographs are the main basis for the diagnosis of this disease.

Post-natal short limbs, flexion and softening of the skull need to be differentiated from osteogenesis imperfecta, cranial clavicle hypoplasia or achondroplasia; premature deciduous teeth need to be associated with histiocytosis, jaw infection and teeth, jaw Diseases such as bone tumors are differentiated; a large amount of phosphorylethanolamine is excreted in the urine, which can be distinguished from other diseases with low phosphatase. Cases with hypercalcemia are mainly caused by X-ray examination and other various causes. Calcemia, such as hyperparathyroidism, infant idiopathic hypercalcemia or vitamin D poisoning, the bone X-ray findings of this disease are similar to rickets, but their serum calcium and phosphorus are normal, and alkali The reduction of sex phosphatase is ineffective by vitamin D treatment, so it is not difficult to identify.

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