Phosphate-diabetes

Phosphate -diabetes is a dominantly linked X chromosome disease with deep impairments of phosphorus-calcium metabolism that can not be restored with conventional doses of vitamin D. In this connection, another name for the disease, rickets, resistant to vitamin D, appeared; But in reality this is not about rickets, but about rickets like diseases.

Etiology, pathogenesis. It is suggested that in the case of phosphate-diabetic, the enzymatic processes of the conversion of vitamin D into active hormone-like substances are violated or the sensitivity of the intestinal epithelium receptors to the action of these metabolites is reduced. Characteristic biochemical features are phosphaturia, hypophosphatemia, increased activity of parathyroid glands, high activity of alkaline phosphatase of blood. Reabsorption of calcium in the intestine is reduced.

Clinical picture. Phosphate-diabetes has similar features with the usual D-deficiency rickets, but differs from it in that there are no signs of general intoxication with this disease, the general condition remains satisfactory. In contrast to rickets, the processes of osteomalacia and osteoid hyperplasia are predominantly expressed in the bones of the lower extremities (curvature of long tubular bones or deformation of knee and ankle joints). Clinically, phosphate-diabetes appears not in the first months of life, but in the second half of life, after the children begin to stand on their legs.

In the absence of treatment, the disease progresses with the growth of the child (dystrophy, total inability to move independently). X-ray reveals the same changes that are characteristic of rickets, but pathology is especially pronounced in the bones of the lower limbs. One of the typical X-ray features is the coarse-fibrous structure of the bone spongy substance.

Similar changes on the part of the bone system can be detected in one of the parents or the influence of the mutant gene is found only in the biochemical blood test, so when suspicion of phosphate-diabetes it is advisable to study the content of inorganic phosphorus in the blood of parents and siblings.

The content of phosphorus in the blood of patients is reduced to 15-20 mg / l, the level of calcium is not changed. A significant increase in the excretion of phosphate in the urine (4-5 times higher than normal) is observed intermittently and depends on the activity of the pathological process.

Treatment. Long-term administration of vitamin D in large doses (40 000-120 000 IU daily) with mandatory monitoring of calcium and phosphorus in the blood. Under the influence of treatment, the activity of alkaline phosphatase decreases rapidly. Treatment begins with lower doses, gradually increasing them. In the case of increased calciuria (according to the Sudkovich trial and biochemical data), the doses are reduced. When the condition improves, maintenance doses of 1000-5000 IU are prescribed with interruptions in treatment for 3-7 days. Vitamin therapy is supplemented by the introduction of phosphorus (foods rich in phosphates, calcium glycerophosphate). Apply oxydevit and other metabolites of vitamin D.

Prevention. The risk of re-birth of a sick child in the family is large and reaches 50%, which should be explained to parents during the medical and genetic consultation.

The Dobre-de-Tony-Fanconi syndrome is also characterized by rickets-like osteopathy, but unlike phosphate-diabetes, it manifests itself with more severe general symptoms-hypotrophy, lower resistance to infection. In addition to phosphaturia, it is characterized by aminoaciduria, glucosuria, impaired renal function to maintain the balance of acids and bases of blood. To restore the function of the renal tubules, vitamin D is used in high doses, as in diabetic phosphate, the protein content of the diet is increased to 6 g / kg, and acidosis is corrected.