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PubMed1990

Linear growth in patients with hypophosphatemic vitamin D-resistant rickets: influence of treatment regimen and parental height.

The effects of different treatment regimens and the influence of parental height on the statural growth of 40 patients with hereditary vitamin D-resistant hypophosphatemic rickets were investigated. Three treatment regimens, each with oral phosphate, were used: vitamin D (0.5 to 2 mg/day), calcidiol (50 to 200 micrograms/day), and 1 alpha-hydroxyvitamin D3 (1 to 3 micrograms/day). Mean duration of follow-up was 9.5 +/- 5.1 years. The results show that (1) there was no acceleration of growth before puberty for the majority of children treated with vitamin D (12/16) or calcidiol (13/15), whereas 1 alpha-hydroxyvitamin D3 promoted catch-up growth in 10 of 16 patients; (2) height gain during puberty was normal, irrespective of the treatment; (3) most vitamin D-treated male and female subjects and calcidiol-treated male subjects had short adult stature, but the majority (75%) of the 1 alpha-hydroxyvitamin D3-treated groups had normal stature; (4) parental stature had little influence on the adult height of male subjects, but that of affected girls was positively correlated (p less than 0.002) with mid-parental height. These results demonstrate that 1 alpha-hydroxyvitamin D3 is superior to vitamin D or calcidiol for improvement of stature of patients with hypophosphatemic vitamin D-resistant rickets, and indicate the importance of parental height in determining the adult height of affected girls.

Body Height↗
PubMed1975

Rickets then and now.

Since the introduction of irradiated ergosterol into our food supply, nutritional vitamin D-deficiency rickets has become an uncommon disease. However, skeletal disorders due to abnormalities of vitamin D function still occur. These disorders can now be classified more exactly into two groups: those in which there is a deficiency of the active metabolite of vitamin D, 1,25-dihydroxyvitamin D, and those in which there is an abnormality of renal tubular function resulting in renal hypophosphatemia despite normal vitamin D metabolism. The various entities of these two groups are described and the theoretical basis of their treatment given.

Dihydrotachysterol↗
PubMed1977

Vitamin D-resistant rickets associated with epidermal nevus syndrome: demonstration of a phosphaturic substance in the dermal lesions.

A 5-year-old boy was found to have severe rickets in association with hyperpigmented, linear, verrucous, epidermal tumors, typical of the epidermal nevus syndrome. Normocalcemia (9.6 mg/dl), hypophosphatemia (2.0 mg/dl), elevated serum alkaline phosphatase concentration (313 IU), decreased renal tubular reabsorption of phosphorus (35%), radiologic evidence of rickets, and lack of response to usual therapeutic doses of vitamin D suggested hypophosphatemic vitamin D-resistant rickets. Therapy with vitamin D in doses to 750,000 IU and oral phosphate, 2.0 gm/day, failed to induce healing of the rickets. A subtotal parathyroidectomy performed when the patient was 9 years old was also without effect. When he was 12 years old several fibroangiomas on the face and left lower limb were excised. Within three months all biochemical abnormalities resolved and radiologic evidence of healing was observed. A portion of excised tissue was homogenized and injection of the supernate into a 6-week-old puppy induced excessive phosphaturia. The data suggest that the rickets was induced by a phosphaturic substance extractable from the tumors.

Calcium↗
PubMed1979

Rickets with alopecia: an inborn error of vitamin D metabolism.

Rickets with alopecia, an inborn error of vitamin D metabolism, is described in two sisters. The rachitic disorder began during the first year of life and was refractory to 50,000 IU of vitamin D2/day. Surprisingly, both children had marked elevations in serum concentrations of 1,25-(OH)2D. Although the molecular basis for this disorder is not evident to date, intestinal end-organ unresponsiveness to exceedingly high levels of 1,25-(OH)2D was present, in addition to hyporesponsiveness of bone to these high levels of the hormone, since normocalcemia was maintained despite elevated serum levels of PTH. Therapy with oral 1,25-(OH)2D3 failed to reverse the disorder, but oral phosphorus supplements resulted in significant radiographic and clinical improvement.

Alopecia↗
PubMed1981

The etiology of enamel hypoplasia: a unifying concept.

In a study of children with chronic disorders of calcium and phosphate homeostasis, enamel hypoplasia was found in hereditary vitamin D-dependency rickets and in hypoparathyroidism, conditions characterized by hypocalcemia, and was not found in X-linked hypophosphatemic rickets, a condition in which the plasma calcium concentration is normal. The occurrence of enamel hypoplasia bore no relation to the plasma phosphate concentration. Enamel hypoplasia has also been reported in other pediatric disorders in which hypocalcemia is a major sign (for example, vitamin D deficiency, prematurity, and neonatal tetany). The existence of enamel hypoplasia in a hypoparathyroid or rachitic patient, when correlated with the chronology of enamel mineralization, helps to establish the time of onset of hypocalcemia. The observations led us to the hypothesis that a low serum calcium concentration during enamel formation is a specific determinant of enamel hypoplasia. This hypothesis may be relevant to the etiology of linear enamel hypoplasia, an endemic lesion of primary teeth in children of many Third World countries that predisposes the teeth to dental caries. The hypothesis may therefore be relevant also in explaining the prevalence of caries in the primary teeth of children in many underdeveloped countries.

Calcium↗
PubMed1981

Vitamin D dependency: replacement therapy with calcitriol?

Nine patients with vitamin D-dependency type I were studied. We observed that treatment with large doses of vitamin D altered the phenotypic expression of the disease, thus making a delayed diagnosis difficult. At the time of entry, eight children had hypocalcemia, and seven had hypophosphatemia. Elevated serum immunoreactive parathyroid hormone and low (less than 3 SD from control mean) 1 alpha,25-dihydroxyvitamin D values were constant findings, with no vitamin D deficiency. Despite the elevated serum iPTH, three children had normal urinary phosphate excretion and five had normal urinary cAMP excretion. In the five children tested before treatment, there was no significant change in renal phosphate excretion during an acute parathyroid hormone infusion, although in all a significant rise of urinary cAMP occured. Treatment with calcitriol (0.25 to 2 microgram/day) returned all the biochemical values to normal within four months. In two patients, both supplemented with vitamin D, histomorphometric analysis of iliac crest biopsies revealed severe osteomalacia. After nine and ten months of treatment with calcitriol, there was histologic evidence for improvement of bone mineralization. Since calcitriol requirements may vary during the course of treatment, careful monitoring of biochemical variables is essential.

Adolescent↗
PubMed1986

Hypophosphatemic rickets/osteomalacia in linear sebaceous nevus syndrome: a variant of tumor-induced osteomalacia.

A severe form of vitamin D-resistant rickets is associated with the linear sebaceous nevus syndrome. We investigated the pathophysiology underlying defective bone mineralization in two individuals and examined the effects of 1,25-dihydroxyvitamin D (1,25(OH)2D, calcitriol) therapy on the clinical and biochemical abnormalities. Both patients had fasting hypophosphatemia, markedly diminished TmP/GFR, and elevated alkaline phosphase activity in the presence of normocalcemia. Before treatment with calcitriol, serum 1,25(OH)2D concentrations were reduced but serum 25-hydroxyvitamin D (25(OH)D) concentrations were normal. Administration of calcitriol increased serum 1,25(OH)2D concentrations and led to an increase in TmP/GFR and serum phosphorus levels and to a decrease in alkaline phosphatase activity. However, the renal tubular maximum for reabsorption of inorganic phosphate, normalized according to glomerular filtration rate, and serum phosphorus levels remained abnormally low even in the patient who also received phosphate supplementation. Bone histomorphologic studies in the adult patient showed extreme osteomalacia, which partially improved with calcitriol. These data demonstrate that the putative skin lesion-derived factor results in both a renal tubular defect in phosphate reabsorption and in 1,25-(OH)2 D deficiency. The vitamin D-resistant rickets of linear sebaceous nevus syndrome is a variant of tumor-induced osteomalacia.

Adult↗
PubMed1987

Nephrocalcinosis and its relationship to treatment of hereditary rickets.

Renal ultrasonography was performed on 23 patients with X-linked hypophosphatemic rickets (XLH) and 11 patients with autosomal recessive vitamin D-dependent rickets (ARVDD). A pattern of increased echogenicity of the renal pyramids (ERP) was identified in 11/23 patients with XLH and 3/11 patients with ARVDD; this ultrasonographic finding has previously been associated with medullary nephrocalcinosis. Patients with XLH and ERP had significantly higher mean serum calcium and phosphate concentrations, more frequent episodes of hypercalcemia, and higher doses of oral vitamin D and phosphate during the first 3 years of therapy. Episodes of hypercalcemia were more frequent when patients received higher doses of vitamin D2 (greater than 4000 IU/kg/day) or 1,25-dihydroxycholecalciferol (greater than 40 ng/kg/day). Episodes of hypercalciuria were significantly increased at doses of greater than 20 ng/kg/day 1,25-dihydroxycholecalciferol. In patients with ARVDD, ERP was also correlated with vitamin D dose and frequency of hypercalcemia episodes. ERP was not associated with an elevation of serum creatinine or loss of urinary concentrating ability in either patient group.

Adolescent↗