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Clinical and biochemical findings in parents of children with vitamin D-dependent rickets Type II.

Vitamin D-dependent rickets type II is a rare disease caused by a disorder of the receptor for 1, 25-dihydroxyvitamin D (1, 25(OH)2D). Several parameters of this receptor-effector system were investigated to obtain biochemical information on the presumed heterozygotes of vitamin D-dependent rickets type II in parents of five patients and in their age-matched controls. It was found that the serum concentrations of 1, 25-(OH)2D and 24,25-dihydroxy-vitamin D (24,25(OH)2D), and the ratio of 1,25-(OH)2D/24,25-(OH)2D differed significantly in the parents from those of the patients and the respective control groups. In the parents' cultured skin fibroblasts, the activity of 25-hydroxyvitamin D-24-hydroxylase induced by 10(-8) mol/L 1, 25-(OH)2D3 ranged from 50 to 82% of that of their controls (versus 1-13% of controls for the patients). The binding capacity of the parents' [3H]1, 25-(OH)2D3 to the nucleus was 38-54% of that of their control subjects (versus 7-27% of controls for the patients). The parents' values were thus in a range between those of the patients and the control groups. These findings suggest that, in the parents, a partial impairment of the receptor system for 1, 25-(OH)2D led to an imbalance of vitamin D metabolism, thus confirming that vitamin D-dependent rickets type II is an autosomal recessive inherited disease. Serum concentrations of 1, 25-(OH)2D and 24, 25-(OH)2D may provide useful parameters for detecting heterozygotes of this disease.

24,25-Dihydroxyvitamin D 3↗

Does growth hormone influence the severity of phosphopenic rickets?

The severity of bone disease in phosphopenic rickets is not correlated with serum phosphate levels. In order to determine whether growth hormone (GH) secretion may influence rachitic changes, we evaluated the 24 h integrated concentration of growth hormone (IC-GH) in five children with phosphopenic rickets. Two patients with marked clinical and roentgenographic rachitic abnormalities had normal IC-GH levels. In contrast, three patients with low IC-GH levels had mild rachitic changes. We suggest that the level of spontaneous GH secretion may be one factor which influences the severity of phosphopenic rickets.

Adolescent↗

Rickets as a complication of intravenous hyperalimentation in infants.

Fifteen newborn infants developed roentgenographic evidence of rickets while on long-term intravenous hyperalimentation. In each instance, the initial diagnosis of rickets was suggested on the chest roentgenogram, where characteristic cupped and frayed upper humeral metaphyses were noted; subsequent knee and wrist roentgenograms substantiated these findings. Factors which may have predisposed to the development of rickets include inadequate doses of vitamin D, prematurity and a rapid change in body weight during hyperalimentation therapy.

Bone and Bones↗

Stereological studies on the epiphyseal growth plate in low phosphate, vitamin D-deficiency rickets with special reference to the distribution of matrix vesicles.

In low phosphate, vitamin D-deficiency rickets normal mineralization is reversibly arrested, and rickets is thus a suitable model for studying factors influencing the mineralization process. Partly on the basis of their distribution within the growth cartilage, the so-called matrix vesicles are considered to play an important role in the process of mineralization and it has been claimed that the distribution pattern is the same in rickets as in normal animals. With the use of modern stereological techniques, our group recently demonstrated a matrix vesicle distribution between the zones of the epiphyseal growth plate in normal rats different from that described earlier. The same bimodal distribution pattern was observed in rachitic rats in the present study, the highest volume density being found in the resting and upper hypertrophic zones and the lowest in the proliferative zone. The volume density differences are explained by differences in the number of vesicles between zones, the variation in mean caliper diameter being small. Our findings are discussed in relation to the proposed theories on matrix vesicle origin. The results seem to support the dynamic cell debris theory for matrix vesicle origin presented earlier, but the existence of subpopulations of matrix vesicles with a specialized function and origin cannot be ruled out.

Animals↗

Calcium metabolism and growth during early treatment of children with X-linked hypophosphataemic rickets.

UNLABELLED: To evaluate the effect of early treatment on calcium metabolism and growth of infants with X-linked hypophosphataemic rickets (XLH), we enrolled eight infants (one boy) with XLH in a prospective study before and during combined treatment with 40 60 mg/kg per day phosphate and 20-40 ng/kg per day 1,25(OH)2D3 (calcitriol). The duration of treatment ranged from 12 to 68 months (median 27 months). We measured the height and several indices of calcium and bone metabolism before and at intervals of 6 weeks to 3 months thereafter during treatment. The diagnosis XLH was established between the age of 3 to 12 weeks by the detection of elevated alkaline phosphatase activities (n = 8) and urinary hydroxyproline (n = 7), whereas only five patients had also hypophosphataemia. Six of seven untreated patients had decreased 1,25(OH)2 vitamin D levels in serum. During treatment alkaline phosphatase and hydroxyproline decreased to normal or slightly elevated levels, whereas serum phosphate remained below the normal range. Several patients treated with more than 40-50 mg/kg per day phosphate developed secondary hyperparathyroidism. One patient receiving a low dose of 20 ng/kg per day calcitriol had prolonged radiological and biochemical signs of rickets and growth delay. The other patients presented with no or only slightly transient signs of rickets. Three patients developed moderate nephrocalcinosis. The statural growth rate decreased slightly below 2 SDs without a further decrease in two patients and remained within the normal range in the other patients. Only four patients developed moderate leg deformities. CONCLUSIONS: Early treatment with calcitriol at a daily dose of at least 30-40 ng/kg and phosphate at a daily dose of maximal 40-50 mg/kg improves mineral metabolism and seems to obviate severe growth delay and leg deformities.

Adolescent↗

Myelofibrosis: an unusual presentation of vitamin D-deficient rickets.

UNLABELLED: We present the case of a breast-fed 5-month-old infant who presented with pancytopenia, secondary to intense myelofibrosis during the winter months because of undiagnosed rickets. The patient responded to oral vitamin D with rapid resolution of symptoms. Secondary hyperparathyroidism was the probable cause of the myelofibrosis. CONCLUSION: Although nutritional rickets remains a problem in developing countries, children in northern climates in industrialized countries may also be at risk. Rickets must be considered when assessing myelofibrosis in a very young child.

Humans↗

A case of osteochondritis dissecans in rickets.

Rickets and the decreased ossification associated with it can give rise to abnormally low bone density and weakened osseous structures. Despite this association, rickets has rarely been associated with osteochondral defects, and the imaging findings of this association have not been previously described on magnetic resonance (MR) imaging. This case report presents an adolescent male with a clinical history of rickets and recent-onset knee pain that was determined to be caused by bilateral osteochondritis dissecans. Prompt recognition of osteochondritis dissecans is important, as this entity is a treatable cause of knee pain.

Child↗

[Osteomalacia and rickets].

Although rickets and osteomalacia posed a serious health problem in industrialised countries a hundred years ago, these diseases are now rarely found, and when, usually in certain risk groups. In underdeveloped countries, rickets is still a major public health problem due to inadequate calcium intake by children. In our highly developed countries, elderly people--especially when institutionalised in nursing homes--are at a very high risk of developing osteomalacia, often combined with pre-existing osteoporosis, with its high impact on mobility and life expectancy in this section of the population. In this review, the common mechanisms involved in developing rickets or osteomalacia are identified and therapeutic measures are reported. Rare causes of osteomalacia due to congenital errors in metabolism or genetic defects are also discussed.

Aged↗

1,25-Dihydroxyvitamin D resistance, rickets, and alopecia.

Two unrelated kindreds with four affected children having 1,25-dihydroxyvitamin D resistance, rickets, and alopecia are described. The children exhibited early onset of severe rickets with hypocalcemia, hypophosphatemia, elevated serum alkaline phosphatase levels, and secondary hyperparathyroidism. Radiography showed diffuse demineralization and classic changes of rickets. All affected children had total-body alopecia. Serum levels of 1,25-dihydroxyvitamin D3 were elevated and rose to extremely high values during treatment, with no apparent change in the mineral disorder. However, secondary hyperparathyroidism and hypophosphatemia did remit during treatment despite persistently low calcium levels. Skin biopsy was performed in the parents and affected children in one kindred. Analysis of 1,25-dihydroxyvitamin D3 receptors in cultured fibroblasts indicated apparent normal receptors in the parents and undetectable receptors in both affected children. After long periods of treatment with vitamin D metabolites and mineral replacement, healing took place in the older child in each kindred. These data suggest that the healing occurred spontaneously as the children reached seven to nine years of age rather than as a result of the treatment. The biochemical lesion in these children appeared to be a genetically transmitted defect in the 1,25-dihydroxyvitamin D3 receptor. The mechanisms by which healing was initiated and maintained remain to be elucidated.

Alopecia↗

Plasma vitamin D metabolite levels in phosphorus deficient rats during the development of vitamin D deficient rickets.

Plasma levels of the vitamin D metabolites were related to changes in bone morphology during the development of rickets in rats deprived of phosphorus and vitamin D. Weanling rats were studied at 1, 3, and 5 wk after onset of diets deficient in phosphorus or in both phosphorus and vitamin D. Bone histology and morphometry were carried out and measurements were made of 45Ca and 32P absorption, serum Ca and P, and plasma 25(OH)D3, 24,25(OH)2D3 and 1,25(OH)2D3. After 1 wk of vitamin D restriction, the plasma levels of 25(OH)D3 and 24,25(OH)2D3 were non-detectable (less than 0.5 and less than 0.8 ng/ml). The plasma 1,25(OH)2D3 level was elevated at 1 wk (105.5 pg/ml) and fell to 19 pg/ml by 5 wk. At 1 wk mild rachitic lesions in epiphyseal cartilage were observed despite the elevated 1,25(Oh)D3 level. Serum Ca and P levels and values for 45CA and 32P absorption decreased and the severity of the rickets increased with the fall in plasma levels of 1,25(OH)2D3. In Vitamin D replete, phosphate deficient rats the epiphyseal cartilage was normal throughout the 5 wk study period. Our results provide further evidence that physiological levels of 1,25 (OH)2 D3 will not prevent rickets without adequate plasma concentrations of either 25(OH)D3 or 24,25(OH)2D3.

Animals↗

Calcitriol treatment in vitamin D-dependent and vitamin D-resistant rickets.

Use of 1,25(OH)2D3 (calcitriol) can be of benefit in the treatment of two hereditary types of rickets and osteomalacia, vitamin D dependency type I (VDD1) and X-linked hypophosphatemic vitamin D-resistant rickets (HPDR). VDD1 is due to inadequate activation of 25(OH)D to 1,25(OH)2D, leading to very low circulating levels of 1,25(OH)2D in plasma; the basic abnormality appears to be an alteration in renal 1 alpha-hydroxylase activity. In VDD1, replacement therapy with calcitriol results in complete correction of the abnormal phenotype. By contrast, in HPDR, plasma levels of 25(OH)D and 1,25(OH)2D are in the normal range, although it has been demonstrated that the ability of patients to produce 1,25(OH)2D under conditions of stress is impaired. When started early in life, the use of phosphate salts in HPDR generally results in healing of rickets, normal growth, and correction of lower limb deformities. However, osteomalacia is not corrected by treatment with phosphate, either alone or in combination with vitamin D. By pharmacologically increasing the level of 1,25(OH)2D3 in these patients, there is often a dramatic improvement in the appearance of the trabecular surface, leading to correction of the osteomalacic component of HPDR; in addition, the secondary hyperparathyroidism observed in previous patients treated with phosphate and vitamin D is easier to control. Closed medical follow-up allows the prevention of renal damage that could result from long-term administration of calcitriol.

Calcitriol↗

Prenatal deficiency of phosphate, phosphate supplementation, and rickets in very-low-birthweight infants.

A preliminary study showed that placental histology was abnormal for babies who subsequently had rickets. The findings--low plasma phosphate concentration; maximum percentage tubular reabsorption of phosphate; and high urinary calcium loss--are those of renal conservation of phosphate in the presence of phosphate deficiency. In a controlled trial no baby receiving phosphate supplements (50 mg per day) had radiological evidence of rickets whereas bone changes were apparent in 42% of the control group. Prenatal deficiency of phosphate, due to placental insufficiency, can be corrected by phosphate supplementation thereby preventing rickets of prematurity.

Calcium↗

Effects of vitamin D metabolites on healing of low phosphate, vitamin D-deficient induced rickets in rats.

A model of low-phosphate, vitamin D-deficient rachitic rats was used to compare the effects of 1 alpha(OH)D3, 1,25(OH)2D3, and 24,25(OH)2D3 on cartilage and bone. The rats were maintained for 3 weeks on a high-calcium, low-phosphate, vitamin D-deficient diet, during which period they developed severe rickets. The rachitic rats were injected for 2 or 3 consecutive days with a physiologic dose of either metabolite. Other littermates were given a single dose of 50,000 IU of cholecalciferol in combination with a normal diet. Samples of cartilage fluid (Cfl) and of blood were removed prior to sacrifice for biochemical studies of some parameters of calcification. These parameters were correlated with the results of light and electron microscopic studies of the growth plate cartilage and bone. Treatment with 1 alpha (OH)D3 or with 1,25(OH)2D3, in spite of increasing Ca and P levels in the Cfl, induced only partial healing of the rickets. In contrast, 24,25(OH)2D3 or vitamin D with a normal diet resulted in complete morphologic and biochemical healing of the rickets. Transmission electron microscopic (TEM) studies have shown partial mineralization of the wide hypertrophic zone of the growth plate following treatment with 1 alpha(OH)D3 or with 1,25(OH)2D3. Mineralization was more complete with 24,25(OH)2D3 treatment. The results of this study emphasize the importance of 24,25(OH)2D3 for normal endochondral bone formation and mineralization.

24,25-Dihydroxyvitamin D 3↗

Studies on rickets and osteomalacia in Bactrian camels (Camelus bactrianus).

Epidemiological studies have indicated incidences of 32.9% and 27.8% for rickets and osteomalacia, respectively, in Bactrian camels (Camelus bactrianus), but there is an increased incidence under drought conditions, sometimes reaching 75%. We have found that concentrations of phosphorus and copper in forage and soil samples in a drought affected area were significantly lower than in a control area or normal reference values (P < 0.01) ; the mean Ca:P ratio in the forages was 50:1. The phosphorus content of blood and hair from affected camels was significantly less than that in controls (P < 0.01) and concentrations of copper in the liver and kidney were significantly lower in affected camels than control animals (P < 0.01); the concentrations of triiodothyronine (T(3)), thyroxine (T(4)) and parathyroid hormone (PTH) in the serum from affected animals were significantly higher than those from healthy controls (P < 0.01); serum inorganic phosphorus and ceruloplasmin levels were lower than those in the controls (P < 0.01 or P < 0.05); the concentrations of serum alpha-globulin and beta-globulin were significantly higher in the affected camels than in the healthy controls (P < 0.01). The pathological changes seen in camels affected with rickets included porous, brittle, light, osteoporotic bones that were susceptible to fractures and had less resistance to cutting and sawing. Wrist joints were enlarged with an apparent bowing of the long bones in forelimb and with typical broadening of the epiphyses. In adult female camels, many enlarged scars were often seen in ribs indicating earlier fractures. The disease could be cured with supplementary bone meal, phosphate or mineral mixtures and in field investigations clinical signs disappeared within 15 days. Over the same period, the concentrations of phosphorus and alkaline phosphatase in blood returned to normal. The disease may be effectively prevented by use of mineral blocks (block salt licks) or dosing orally with copper, selenium and cobalt soluble glass boluses. We conclude that rickets and osteomalacia are mainly caused by phosphorus and copper deficiencies in the pasture.

Animal Feed↗

Vitamin D deficiency rickets as a late complication of the short gut syndrome during infancy.

Four infants with less than 35 cm of jejunum and ileum remaining following neonatal operations and after being weaned from long-term total parenteral nutrition onto an "elemental" formula, developed the syndrome of vitamin D deficiency rickets at 9-15 mo of age. The diagnosis of rickets was confirmed by biochemical and radiographic findings. Serum 25 hydroxy vitamin D (25 OHD) values were significantly lower than normal and oral 25 OHD absorption studies indicated severe vitamin D malabsorption. This report emphasizes the importance of prospective assessment of all neonates having distal ileal resection to detect the early stages of vitamin D deficiency rickets.

25-Hydroxyvitamin D 2↗

Rickets in children of rural origin in South Africa: is low dietary calcium a factor?

Studies of nine children 4 7/12 to 13 years of age who had rickets are presented. No evidence of renal abnormalities, vitamin D deficiency, or of the inherited varieties of rickets was found. The salient features were their rural origins, mild hypocalcemia with evidence of secondary hyperparathyroidism, and improvement with a normal diet that contained an average of 944 mg calcium/24 hours. It is proposed that the etiology of the rickets is related to low calcium intake with or without a high oxalate concentration in the diet.

Adolescent↗

Pathogenesis of rickets in chronic hepatobiliary disease in children.

To investigate whether hepatobiliary rickets is caused by defective intestinal absorption of vitamin D or by impaired hepatic hydroxylation of the vitamin, we studied three children who developed severe rickets, hypocalcemia, and hypophosphatemia, two despite having received 400 to 800 IU vitamin D per day by mouth, and one despite prolonged treatment with 10,000 IU daily. On oral vitamin D therapy, plasma vitamin D and 25-hydroxyvitamin D levels were low. When two children were treated with weekly intravenous doses of 3,000 IU vitamin D to approximate the recommended prophylactic allowance, their plasma calcium and phosphate values improved promptly, the radiographic lesions healed, and the plasma concentrations of vitamin D and 25-hydroxyvitamin D became normal. Our studies indicate that the primary cause of hepatobiliary rickets is intestinal malabsorption of vitamin D, not impairment of the hepatic metabolism of the vitamin.

Biliary Tract Diseases↗

Spironolactone-reversible rickets associated with 11 beta-hydroxysteroid dehydrogenase deficiency syndrome.

A 7-year-old girl had growth retardation, hypertension, and hypokalemic alkalosis. Baseline serum aldosterone concentration and plasma renin activity were low and unresponsive to sodium deprivation and to orthostatic changes. Baseline serum progesterone, 17-hydroxyprogesterone, 11-deoxycortisol, and cortisol levels were normal and adequately responsive to ACTH stimulation. No steroid was found abnormally elevated. A diagnosis of 11 beta-hydroxysteroid dehydrogenase deficiency was established on the basis of elevated urinary tetrahydrocortisol plus allotetrahydrocortisol/tetrahydrocortisone ratio, determined by gas chromatography-mass spectrometry. Evaluation of bone mineral metabolism and parathyroid function, and skeletal radiographs, revealed the presence of rickets and secondary hyperparathyroidism. Treatment with spironolactone alone for 2 months corrected hypertension, hypokalemic alkalosis, and all laboratory and radiologic evidence of rickets and hyperparathyroidism, resulting in acceleration of growth rate. The response to spironolactone suggests that a hypermineralocorticoid state is responsible for the hypertensive syndrome and that rickets and hyperparathyroidism could be a consequence of excess mineralocorticoid activity.

11-beta-Hydroxysteroid Dehydrogenases↗