Rickets and osteochondrosis are disorders of mineralization of the newly synthesized matrix. In adults, the disease involves only the bones and is called osteochondrosis; in children, the disease also occurs in the growth plates and cartilage to be mineralized, resulting in characteristic skeletal deformities called rickets. Low phosphorus rickets is a disease characterized by low blood phosphorus, bone pain, and weakness of the limbs.
1.Etiology
Low phosphorus osteomalacia is mainly related to genetics. These include X-linked hypophosphatemic rickets (XLH), autosomal dominant hypophosphatemic rickets (ADHR), hereditary hypophosphatemic rickets combined with hypercalcemia (HHRH), and X-linked recessive hypophosphatemic rickets (XRHR). There are also acquired causes, such as tumor osteomalacia (TIO).
2. Clinical manifestations
Symptomatic individuals vary between early childhood and adult patients. Children generally have early onset of the disease, with low blood phosphorus shortly after birth, and bone lesions similar to vitamin D deficiency rickets begin to appear around the age of 1 week, with deformities of the lower extremities often being the earliest symptom to draw attention to, but mild cases are often overlooked, and height is mostly normal. Severe disease, such as active rickets, can appear in children around 6 years of age, manifesting as severe skeletal deformities, dwarfism, severe bone pain, and some patients can be unable to walk due to skeletal pain. Fractures and growth arrest may occur, and dental lesions, such as broken teeth, wear and tear, loss of enamel, etc., often appear early before the onset of bone disease. Adults often show chondromalacia, hypotonia, especially in the lower extremities, and hand and foot twitches are rare. Women often have only low blood phosphorus without bone disease, and very low blood phosphorus, often 0.32-0.78 mmol/L (1-2.4 mg/dl), more pronounced in children, and increased urinary phosphorus. Serum and urine calcium and magnesium are normal or slightly low, blood calcium and phosphorus product is below 30, serum alkaline phosphatase is mostly normal or slightly high (determined by bone disease), blood parathyroid hormone (PTH) is normal or slightly high, blood 1,25(OH)2D3 level is mostly normal, but there are also those who are reduced.
3.Examinations
1.Urine examination
Urine phosphorus increase, urine calcium and magnesium, normal or slightly low.
2, blood biochemical examination
(1) blood phosphorus is low, often 0.32-0.78mmol/L (1-2.4mg/dl). Blood calcium and magnesium is normal or slightly low, blood calcium and phosphorus product is below 30. Blood alkaline phosphatase is elevated during the active phase. Blood parathyroid hormone (PTH) is normal or slightly elevated, and blood 1,25(OH)2D3 level is mostly normal, but may be decreased.
(2) Routine imaging and ultrasound examinations are performed. Bone X-ray shows typical rickets and osteochondrosis signs.
4.Diagnosis
Based on the above clinical manifestations and laboratory test results, the diagnosis is not difficult.
5.Differential diagnosis
1.Vitamin D deficiency rickets
It is mainly due to vitamin D deficiency. Familial anti-vitamin D rickets or osteochondrosis mostly have clear causes of vitamin D deficiency. Low or normal blood calcium, low blood phosphorus, but no increase in urinary phosphorus and better response to vitamin D treatment can be differentiated. In addition, the absence of increased urinary phosphorus, increased blood parathyroid hormone levels, and elevated urinary cAMP may also help to differentiate.
2. Vitamin D-dependent or pseudo-vitamin D deficiency rickets
Familial anti-vitamin D rickets or osteochondrosis with heavy convulsions and muscle weakness, low blood calcium, normal or increased blood phosphorus, good response to physiological doses of 1,25(OH)2D3 treatment, and dependence.
3.Other
Such as Fanconi syndrome, renal tubular acidosis, chronic renal failure and other causes of nephrogenic rickets.
6.Complications
Rickets or osteochondrosis, developmental disorders, skeletal deformities, severe muscle weakness, etc.
7.Treatment
1.Vitamin D and its metabolites
Supplementation of vitamin D such as taking vitamin D2, which must be taken in very large doses or vitamin D orally, or intramuscular injection of vitamin D2 and vitamin D3, or 1α-(OH)D3 or 1,25(OH)2D3. The course of treatment depends on the specific case. Recent data confirm that oral phosphorus and 1,25(OH)2D3 result in a significant reduction in bone pain in nearly 90% of cases. The dose should be adjusted according to the patient’s blood calcium, phosphorus, urine calcium and bone X-ray to prevent hypercalcemia during treatment. High urinary calcium is a precursor to hypercalcemia. Vitamin D treatment alone often cannot completely cure bone disease, nor can it correct low blood phosphorus, so it needs to be combined with phosphate treatment.
2, high phosphorus diet or the application of phosphate combination.
3.Etiology treatment
Some due to tumor should be removed.
8.Prognosis
Low phosphorus rickets, if appropriate treatment is taken in time, the prognosis is generally good.
9.Prevention
Familial anti-vitamin D rickets or osteochondrosis is a family genetic disease, and there is no special prevention method for its development.