Pseudohypoparathyroidism in children

Introduction to pediatric pseudoparathyroidism Pseudoparathyroid hypoplasia is a rare familial disease in which the target cells are incomplete or completely unresponsive to PTH. Clinically, there are symptoms of hypoparathyroidism, hypocalcemia, hyperphosphatemia, and normal or high blood PTH concentrations. Often accompanied by a variety of congenital growth and skeletal development defects. Pseudohypoparathyroidism (Pseudohypoparathyroidism, PHP), also known as Seabright-Bantam syndrome. The symptoms include hypoparathyroidism with hypoparathyroidism (referred to as pseudohypothyroidism) and pseudohypoparathyroidism (referred to as false pseudohypothyroidism). basic knowledge The proportion of illness: 0.001% Susceptible people: children Mode of infection: non-infectious Complications: dwarfism cataract

The cause of pseudohypoparathyroidism in children

(1) Causes of the disease

The disease is a different type of X-chain-locked hereditary disease. The basic obstacle is that the target cells do not respond completely or completely to PTH. This abnormality in PTH reaction involves binding of PTH and receptor to target cells. The various steps of a series of reactions, the currently known defects: in this patient's red blood cells, coupled with the PTH receptor adenylate cyclase system; the regulation of the bird nucleotide-sensitive regulatory protein, the target organ tissue PTH does not respond, or the structure of parathyroid hormone is abnormal, and it is not recognized by PTH receptors. PTH promotes the abnormal action of 1,25(OH)2D in the kidney, and PTH can not function.

(two) pathogenesis

Parathyroid tissue is normal, PTH secretion is normal, blood PTH is normal or high, but there is still hypocalcemia and hyperphosphatemia. Parathyroid compensatory hypertrophy is the target organ cell weakened or completely lack of PTH response. , generally divided into 2 types, pseudo-parathyroidal low type I, is a receptor defect on the target cell membrane, can not accept PTH, can accept but can not activate the adenylyl cyclase system, can not synthesize cAMP, give PTH urinary cAMP not Increased and thus PTH can not exert physiological effects, injection of exogenous PTH, hypocalcemia, high blood phosphorus is still not corrected, pseudo-parathyroidal low type II is injected after exogenous PTH, urinary tract cAMP increased, and phosphorus excretion No increase, low blood calcium and high blood phosphorus are not corrected, is a post-receptor defect.

The disease is a dominant hereditary X-chain-locked inheritance.

Prevention of pediatric pseudoparathyroidism

Pseudohypoparathyroidism is a familial disease that is markedly inherited by different exogenous X-chains. Therefore, the most effective prevention method is pre-marital examination and prenatal examination. Amniotic fluid can be used for prenatal examination. Puncture examination, blood test for pregnant women, etc.

Pseudohypoparathyroidism complications in children Complications dwarf cataract

Congenital malformations, exostosis, heterotopic ossification, fibrocystic osteitis, etc., can occur with dwarfism, mental retardation, cataract, and hypogonadism.

Symptoms of pediatric pseudoparathyroidism common symptoms hypocalcemia slow growth alkaline phosphatase increased abnormally short mental retardation youth cataract metacarpal and humerus short

Clinical features In addition to low hypocalcemia near the parathyroid, there are congenital bones and other developmental deformities, such as dwarfism, round face, mental retardation, small mandibular, thin neck, heterotopic ossification, etc., such as kidney non-reaction When bone tissue responds to PTH, subperiosteal absorption, fibrocystic osteitis, is called fibrotic osteitis pseudohypoparathyroidism.

The child has sputum, short stature, short thumb, short 1, 2, 4 metacarpal and humerus, occasionally the second finger is longer than the middle finger, short toe, exogenous epiphysis, thickening of the skull and growth disorders, common There are translocation calcium deposition and subcutaneous migration osteogenesis, basal ganglia calcification and crystalline cataract. Children often have the above anatomical features. PTH resistance can also be accompanied by hypogonadal function, also caused by Gs gene mutation, blood calcium reduction, phosphorus And alkaline phosphatase can be elevated, blood PTH increased or normal.

Examination of pediatric pseudoparathyroidism

1. Blood biochemical examination blood calcium decreased, blood phosphorus increased.

2. After the Ellsworth-Howard test is administered with 200 U (2 ml) of PTH (injection), if the urinary phosphorus is discharged 5 to 6 times more than the original, it means that the primary hypoparathyroidism is reduced, that is, the renal tubules respond well to PTH. If the increase is less than 2 times, it is the disease. If the cAMP in the urine can be measured at the same time, if the cAMP is increased, and the urinary phosphorus is also more, the primary hypoparathyroidism, such as only cAMP increase, is an intrinsic II. Type II indicates that the second messenger function is destroyed. If the urinary phosphorus and cAMP are not increased, it is intrinsic type I (Drezner classification: no difference in urinary phosphorus and cAMP after PTH type I; type II is no increase in urinary phosphorus) , but cAMP increased).

3. X-ray bone examination can be seen in various deformities, such as short finger toe deformity, thickening of the skull, exostosis, heterotopic ossification, and fibrous osteitis.

4. EEG examination can find abnormal brain waves.

Diagnosis and diagnosis of pediatric pseudoparathyroidism

Children with clinical manifestations of hypocalcemia, hyperphosphatemia and normal renal function, patients with mental retardation or mental disorders in the family or with such patients should consider the possibility of this disease and further laboratory tests.

PTH test: intravenous injection of PTH, dosage: infant 8U/kg, maximum 200U/time, 24h urine cAMP concentration before and after injection of PTH, calculate the amount of increase after injection, compared with normal control reaction, or PTH injection (intramuscular) 200U, for 3 consecutive days, blood calcium still does not rise, indicating no response to PTH.

Identification with hypothyroidism, the above laboratory tests can help identify.

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