Effects of therapy in X-linked hypophosphatemic rickets

Article Abstract:

Rickets is a vitamin D deficiency syndrome that results in defective bone development. The symptoms of rickets may also result from a genetic defect known as X-linked hypophosphatemic rickets. Patients with this genetic disorder have impaired reabsorption of phosphate in the proximal tubules of the kidneys, as well as deficient production of 1,25-dihydroxyvitamin D. Administering phosphate to replace that lost from the kidneys does not correct the defect, nor does vitamin D supplementation. However, the simultaneous use of both helps raise the level of phosphate in the blood and improve the bony defects. The degree to which this therapy is helpful has been uncertain. The question is not trivial, since evidence indicates that the treatment itself may cause nephrocalcinosis, an accumulation of calcium in the kidney, which can lead to kidney failure. Clearly, a treatment that risks kidney failure can be justified only if it provides very significant benefits to the patient. A study was conducted to evaluate the effects of phosphate and vitamin D therapy in 24 children, age one to 16 years. Therapy was given for 0.3 to 11.8 years. Patient height was scored by determining the relative difference between the patients and the standard growth curves; the height score was expressed as the number of standard deviations (SDs) below the average height for a particular age and sex. Furthermore, ultrasound imaging of the kidneys was performed to detect the earliest indications of nephrocalcinosis. The results show that the treated patients were an average of 1.08 SD units shorter than average, significantly different from the 2.05 SD deficiency historically established for such patients. A total of 79 percent of the patients had mild indications of nephrocalcinosis, which correlated with the dose of phosphate used in treatment, but not the duration of treatment or the dose of vitamin D. The results confirm the effectiveness of combination therapy with phosphate and vitamin D, but indicate that nephrocalcinosis is a great risk. Patients with X-linked hypophosphatemic rickets undergoing such therapy should be monitored regularly for nephrocalcinosis. Since there is little benefit to therapy after growth is completed, the treatment should not be continued any longer than necessary. (Consumer Summary produced by Reliance Medical Information, Inc.)

Drug therapy, Rickets, Hypophosphatemia, Metabolism, Inborn errors of, Inborn errors of metabolism, Vitamin D deficiency

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Normal or early development of puberty despite gonadal damage in children treated for acute lymphoblastic leukemia

Article Abstract:

The timing of sexual development during puberty and the functioning of the ovaries and testes was studied in 20 girls and 25 boys who survived acute lymphoblastic leukemia treated with chemotheraphy and radiation of the brain. (Lymphoblastic leukemia is cancer of the disease-fighting white blood cells in the lymph system, which returns these cells to the blood from where they have been working.) Damage to the cells of the ovaries and testes was evident. This damage was confirmed in the boys by the absence of sperm-producing cells in tissue samples from the testes and by the small size of the testes given the development of pubic hair. Only 45 percent of the leukemic girls had detectable levels of inhibin in the blood, which inhibits production of the hormone that causes eggs to grow in the uterus, compared with 93 percent of normal girls. Despite ovarian damage, the affected girls began menstruating at the age of 12, a year earlier than normal girls. Thirteen out of 23 boys reached puberty at an average age of 12.3 years. Treatment for acute lymphoblastic leukemia can lead to damage of the ovaries or testes regardless of age treatment. But such treatment causes secondary sexual characteristics (pubic hair, for example) of puberty to develop at a normal age in boys and a bit earlier than normal in girls.

Analysis, Abnormalities, Complications and side effects, Testis, Child development, Puberty, Reproductive organs, Genitalia, Luteinizing hormone, Chemotherapy, Combination, Combination chemotherapy, Biopsy, Follicle-stimulating hormone

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A boy with vertebral compression fractures

Article Abstract:

A six-year-old boy with spinal fractures was diagnosed with acute lymphoblastic leukemia. He was successfully treated and had no new fractures on follow-up.

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