OVERVIEW
Rickets and osteochondrosis are disorders of mineralization of 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 the characteristic skeletal deformity called rickets. Hypophosphatemic rickets is a disease characterized by low blood phosphorus, bone pain, and weakness of the limbs.
Etiology
Hypophosphatemic osteomalacia is primarily genetically related. These include X-linked hypophosphatemic rickets (XLH), autosomal dominant hypophosphatemic rickets (ADHR), hereditary hypophosphatemic rickets combined with hyperuricemia (HHRH), and X-linked recessive hypophosphatemic rickets (XRHR). There are also acquired causes such as tumor osteochondrosis (TIO).
Symptoms
Symptomatic individuals vary between early childhood and adult patients. Children usually have an early onset of symptoms, low blood phosphorus shortly after birth, and bone lesions similar to vitamin D-deficiency rickets begin to appear around the age of 1 year. Lower limb deformities are often the earliest symptom that attracts attention, but mild cases are often overlooked, and height is often normal, and there are cases of short stature due to growth disorders. Severe cases, such as children at about 6 years of age can appear typical active rickets, manifested by severe skeletal deformities, dwarfism, severe bone pain, some patients may be unable to walk due to bone pain. Fractures and growth retardation may occur, and dental lesions, such as fracture, wear and tear, loss of teeth, and low enamel, often appear early before the onset of bone disease. Adults often show chondromalacia, hypotonia, especially in the lower limbs, hand and foot twitching is less common, women often only have low blood phosphorus without bone disease, blood phosphorus is very low, often 0.32 to 0.78 mmol / L (1 to 2.4 mg / dl), children’s cases are more obvious, and increased urinary phosphorus. Calcium and magnesium in serum and urine are normal or slightly low, the product of blood calcium and phosphorus 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, and the blood level of 1,25(OH)2D3 is mostly normal, but there are some people with reduced levels.
Examination
1. Urine examination
Urine phosphorus is increased, calcium and magnesium in urine are 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 are normal or slightly low, and the product of blood calcium and phosphorus is below 30. Blood alkaline phosphatase is elevated during the active phase. Blood parathyroid hormone (PTH) is normal or slightly high, and blood 1,25(OH)2D3 level is mostly normal, but there are also people with reduced levels.
(2) Routine imaging and ultrasound are performed. Bone X-ray shows typical signs of rickets and osteochondrosis.
Diagnosis
Based on the above clinical manifestations and laboratory findings, the diagnosis is not difficult.
Differential diagnosis
1. Vitamin D deficiency rickets
Mainly due to vitamin D deficiency, familial anti-vitamin D rickets or osteochondrosis mostly have a clear cause of vitamin D deficiency. Low or normal blood calcium, low blood phosphorus, but the urine phosphorus does not increase and the amount of vitamin D treatment responds well, can be differentiated. In addition, the absence of increased urinary phosphorus, increased levels of parathyroid hormone, and elevated urinary cAMP can also help to differentiate.
2. Vitamin D-dependent or pseudo-vitamin D deficiency rickets
Familial anti-vitamin D rickets or osteomalacia with severe convulsions and muscle weakness, low blood calcium, normal or increased blood phosphorus, good response to physiologic doses of 1,25(OH)2D3 treatment, and is dependent.
3.Other
Such as Fanconi syndrome, renal tubular acidosis, chronic renal failure and other causes of renal rickets.
Complications
Rickets or osteomalacia, developmental disorders, skeletal deformities, severe muscle weakness.
Treatment
1. Vitamin D and its metabolites
Supplementation of vitamin D such as vitamin D2, which must be taken in very large doses or vitamin D orally, or intramuscular injection of vitamin D2 and vitamin D3, and also 1 alpha-(OH)D3 or 1,25(OH)2D3. The course of treatment is determined on a case-by-case basis. Recent data confirms that oral administration of phosphorus and 1,25(OH)2D3 results in a significant reduction of bone pain in nearly 90% of cases. Dosage should be adjusted according to the patient’s blood calcium and phosphorus, urinary calcium and bone X-ray performance during treatment to prevent hypercalcemia. High urinary calcium is the precursor of hypercalcemia. Vitamin D treatment alone often cannot completely cure bone disease, nor can it correct hypophosphatemia, so it is necessary to cooperate with the treatment of phosphate.
2. High-phosphorus diet or application of phosphate combinations.
3. Treatment of etiology
Certain tumors should be removed.
Prognosis
The prognosis of hypophosphatemic rickets is generally good if appropriate treatment is taken in time.
Prevention
Familial anti-vitamin D rickets or osteochondrosis is a kind of family hereditary disease, there is no effective preventive method for its onset, and patients who have already developed the disease should be actively treated symptomatically to prevent the occurrence of complications.