Familial vitamin D-resistant rickets

Introduction to familial anti-vitamin D rickets Familial anti-vitamin D rickets or osteomalacia (familialvitamin Dresistantricketsorosteomalacia), also known as primary hypophosphatemic rickets, hypophosphatemic rickets (hypophosphatemicrickets) is a familial hereditary tubular dysfunction. basic knowledge The proportion of illness: 0.002% Susceptible people: no special people Mode of infection: non-infectious Complications: rickets Myasthenia gravis

Familial anti-vitamin D rickets

Cause:

The pathogenesis of this disease has not been fully defined. It has been previously thought to be caused by abnormal vitamin D metabolism or intestinal calcium absorption disorder, but the blood level of 1,25(OH)2D3 is normal, and the administration of this drug can not correct the low blood. Phosphorus and excessive urinary phosphorus excretion rate, so the evidence is insufficient. At present, it is considered that the renal tubule itself has functional defects, which may be the lack of a phosphorus-binding protein, thus affecting the normal transfusion of phosphorus in the intestinal and renal tubular epithelium. It is generally believed that the genetic person may have a special genetic defect in the distal renal tubule, the phosphorus transport system that responds to parathyroid hormone and the function of synthesizing 1,25(OH)2 cholecalciferol, and the renal tubule is heavy on phosphorus. Reduced absorption, increased urinary phosphorus, causing blood phosphorus to decrease, due to decreased intestinal calcium absorption, so blood (Ca) × (P) product decreased and affected bone calcification, and caused hypocalcemia, secondary parathyroid function Hyperthyroidism and osteomalacia, caused by dysentery and osteocalcification, secondary diseases such as giant cell tumors (benign or malignant), repair granuloma, hemangioma, fibroids, etc., due to the secretion of humoral factors May be damaged Proximal tubular to 1-hydroxylation of 25(OH)D and phosphate transport, renal phosphate clearance increased, and osteomalacia and hypophosphatemia, under the influence of the above factors, ultimately cause growth Developmental disorders and obvious bone disease.

Familial anti-vitamin D rickets prevention

The disease is a family hereditary disease, there is no specific preventive measures for its onset, and patients with already onset should be actively symptomatic to prevent complications.

Familial anti-vitamin D rickets complications Complications rickets myasthenia gravis

Rickets or osteomalacia; developmental disorders, skeletal deformities, severe muscle weakness, etc.

Familial anti-vitamin D rickets symptoms Common symptoms Bone pain, bone softening, chronic renal insufficiency, convulsions, vitamin D deficiency, urinary phosphorus, hypophosphatemia, hypophosphatemia

The disease is rare, often with a family history, more common in women, but the clinical symptoms are light, male patients are the opposite.

Most of the patients in this disease can be asymptomatic, but generally have different degrees of clinical manifestations. Symptoms are different in early childhood and adult patients. The child usually has early onset, and there is hypophosphatemia soon after birth. Most of the bone lesions similar to vitamin D deficiency rickets begin to appear around 1 year old. The "O" shaped leg is often the earliest symptom of attention, but the disease is mostly neglected. The height is normal, and the sick children are short stature due to growth and development disorders; serious diseases such as children can have typical active rickets at the age of 6 years, manifested as severe skeletal deformities, dwarfism, severe bone pain.

Some patients may suffer from bone pain and can not walk, patients may have fractures and growth and development stagnation, and often occur before the occurrence of bone disease, early dental lesions, such as broken teeth, wear, shedding, enamel too small, etc., adults often manifest as cartilage Disease, but there is no secondary hyperparathyroidism and Looser-Milkman sign on X-ray films. The muscle tension is low, especially in the lower limbs. Hand and foot twitching is rare.

Women often have only low blood phosphorus and no bone disease, blood phosphorus is very low, often 0.32 ~ 0.78mmol / L (1 ~ 2.4mg / dl), children's cases are more obvious, and urinary phosphorus increased, serum and urine calcium and Magnesium is normal or slightly lower, blood calcium, phosphorus product is below 30, serum alkaline phosphatase is normal or slightly higher (determined by bone disease), blood parathyroid hormone (PTH) is normal or slightly higher, blood l, 25 ( OH) 2D3 levels are normal, but there are also reductions. Treatment with vitamin D such as adequate phosphate supplementation can work, intravenous calcium can also have a transient effect.

Familial anti-vitamin D rickets check

Urine check

Increased urinary phosphorus, normal or slightly lower calcium and magnesium in urine, normal urine cAMP.

2. Blood biochemical examination

Low blood phosphorus, usually 0.32 ~ 0.78mmol / L (1 ~ 2.4mg / dl), blood calcium and magnesium normal or slightly lower, blood calcium, phosphorus product below 30, blood alkaline phosphatase increased in active period, Blood parathyroid hormone (PTH) is normal or slightly higher, and blood 1,25(OH)2D3 levels are also normal, but there are also reductions.

Routine imaging examination and B-ultrasound examination, bone X-ray showed typical signs of rickets and osteomalacia.

Diagnosis and identification of familial anti-vitamin D rickets

Diagnostic criteria

According to the above clinical manifestations and laboratory results, the diagnosis is not difficult.

1. There are typical clinical manifestations such as obvious rickets or osteomalacia (the lower limbs are obvious). The pediatric patients have early onset, and there is hypophosphatemia soon after birth. Skeletal lesions appear around 1 year old, especially the "O" leg. Common early symptoms that cause attention.

2. Hypophosphatemia, increased renal phosphorus clearance, and increased urinary phosphorus.

3. Intestinal absorption of calcium and phosphorus is reduced.

4. No response to general therapeutic doses of vitamin D.

5. Have a positive family history or a history of hypophosphatemia.

6. Exclusion of vitamin D deficiency, chronic renal insufficiency, bone disease caused by other renal tubular dysfunction diseases, those with the above points, and can be discharged from other causes of renal rickets can consider the diagnosis of this disease.

Differential diagnosis

The disease should be identified with the following diseases:

1. Vitamin D deficiency rickets

Mainly due to vitamin D deficiency, the disease has a clear cause of vitamin D deficiency, low or normal blood calcium, low blood phosphorus, but urinary phosphorus does not increase and respond to vitamin D treatment, can be identified, In addition, urinary phosphorus does not increase, blood parathyroid hormone levels increase, and urinary cAMP increases, which also helps to identify.

2. Vitamin D-dependent or pseudo-vitamin D deficiency rickets

The convulsion and muscle weakness of this disease is heavier, blood calcium is low, blood phosphorus is normal or increased, and the response to physiological dose of 1,25(OH)2D3 is good and dependent.

3. Other

Such as Fanconi syndrome, renal tubular acidosis, chronic renal failure and other renal rickets.

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