Neonatal hypophosphatemia

Introduction Vitamin D-resistant rickets are a type of tubular genetic defect that has both hypophosphatemia and hypocalcemia. Familial hypophosphatemic rickets are caused by renal tubular defects and loss of phosphorus in the kidneys, resulting in disorder of calcium and phosphorus metabolism, causing rickets. The genetic method is sexually induced and inherited, and it has no response to the general physiological dose of vitamin D, so it is also called anti-vitamin D rickets and sexually linked hypophosphatemia.

Cause

The disease manifests as X-linked dominant inheritance, mainly due to the mutation of the PHEX gene located on the X chromosome, resulting in a decrease in renal tubular absorption of phosphorus.

an examination

Related inspection

Serum inorganic phosphorus biochemical examination blood routine

The main biochemical abnormalities seen in the laboratory are hypophosphatemia, but attention should be paid to the relationship between gender, age and serum. The serum phosphorus value decreased by 0.480.97mmol/L (1.53.0mg/dl), mostly at 0.65mmol/L (2mg/dl), the serum calcium value was normal or slightly decreased, and the serum alkaline phosphatase activity was increased, although it existed. Hypophosphatemia, but urinary phosphorus is still excreted, indicating a reabsorption of phosphorus by the renal tubules. Amino aciduria, glucoseuria, phosphate and potassium have never been found. It has been found that even in the first few months of life, the serum phosphorus concentration may be normal due to the relatively low glomerular filtration rate in the first few months of life. So the earliest laboratory abnormalities may be an increase in serum alkaline phosphatase activity. Urine routine and renal function are normal, and the renal tubular absorbing rate is reduced. X-ray bone fragments can be seen in varying degrees of rickets, and active and recovery lesions coexist, and the femur and tibia are most easily detected. There are bone age, knee valgus or inversion. The metaphysis is widened, fragmented, and the trabecular bone is thick. A cup-like change can occur at the proximal and distal humerus and at the metaphysis of the distal femur, tibia, and ulna.

Differential diagnosis

1, the identification of vitamin D deficiency rickets: (1) Vitamin D intake has exceeded the general demand and there is still active rickets bone changes. (2) There is still activity of active rickets after 2 to 3 years old. (3) Intramuscular injection of 400,000 to 600,000 U of vitamin D, the blood phosphorus increased in a few days for children with general D deficiency rickets, and the long bone X-ray showed improvement in 2 weeks, but the patients did not have these changes. (4) Hypophosphatemia is common among family members and is a feature of low phosphorus anti-D rickets.

2, with low blood calcium anti-vitamin D rickets identification: also known as vitamin D dependent rickets (vitamin D dependent rickets), less common, due to the lack of 1-hydroxylase in the kidney, can not synthesize 1,25- (OH ) 2D3. The onset time is often accompanied by muscle weakness from several months after birth, and early hand and foot sputum can occur. Blood calcium is reduced, blood phosphorus is normal or slightly lower, blood chlorine is increased, and amino acid urine can occur. Although it is treated with conventional dose of vitamin D, it still shows signs of rickets on X-ray long bone tablets. To increase the amount of vitamin D to 10,000 U / d or dihydrotachysterol (DHT) 0.2 ~ 0.5 mg / d to see the effect. Healed with 0.25 to 2 g of 1,25-(OH)2D3. This disease is generally autosomal recessive.

3, other: In addition, the disease must be identified with Fanconi syndrome and renal tubular acidosis.

The main biochemical abnormalities seen in the laboratory are hypophosphatemia, but attention should be paid to the relationship between gender, age and serum. The serum phosphorus value decreased by 0.480.97mmol/L (1.53.0mg/dl), mostly at 0.65mmol/L (2mg/dl), the serum calcium value was normal or slightly decreased, and the serum alkaline phosphatase activity was increased, although it existed. Hypophosphatemia, but urinary phosphorus is still excreted, indicating a reabsorption of phosphorus by the renal tubules. Amino aciduria, glucoseuria, phosphate and potassium have never been found. It has been found that even in the first few months of life, the serum phosphorus concentration may be normal due to the relatively low glomerular filtration rate in the first few months of life. So the earliest laboratory abnormalities may be an increase in serum alkaline phosphatase activity. Urine routine and renal function are normal, and the renal tubular absorbing rate is reduced. X-ray bone fragments can be seen in varying degrees of rickets, and active and recovery lesions coexist, and the femur and tibia are most easily detected. There are bone age, knee valgus or inversion. The metaphysis is widened, fragmented, and the trabecular bone is thick. A cup-like change can occur at the proximal and distal humerus and at the metaphysis of the distal femur, tibia, and ulna.

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