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Etiology of rickets in Nigerian children.

We studied 26 Nigerian children with active rickets (13 boys, 13 girls), aged 1 to 5 years, and compared results of biochemical studies with those of healthy control subjects. The plasma 1,25-dihydroxyvitamin D level was elevated (568 +/- 317 pmol/L) and the 25-hydroxyvitamin D level was (36 +/- 28 mol/L) in the children with rickets compared with the control subjects (369 +/- 134 nmol/L and 69 +/- 22 nmol/L, respectively). The results suggest that rickets in Nigeria is largely the result of calcium deficiency and that vitamin D deficiency and possibly end organ resistance may be contributory factors.

Calcium↗

[Nutritional rickets in childhood: analysis of 62 cases].

BACKGROUND AND OBJECTIVE: Until recently, rickets secondary to vitamin D deficiency was considered a medical oddity rather than a clinical reality in Catalonia (Spain). However, recent data show a reemergence of the disease in the infancy. PATIENTS AND METHOD: Retrospective clinical survey of epidemiologic and clinical features of infants and children (34 boys and 28 girls) diagnosed of nutritional rickets in pediatric departments of Catalonia (Spain) over the last 10 years. RESULTS: Mean age (SD) at diagnosis was 9.9 (7) months (range: 3-36), 35.5% were under 6 months. Race distribution: blacks 61.3%, dark-skinned 36%; white 6.4%. Country of origin: Sub-Saharan Africa 59.7%, Morocco 33.9%, Catalonia 3.2%, Pakistan 1.6%. Seasonal distribution: 60% were diagnosed in autumn and winter. At diagnosis, 72% were following an exclusive milk diet (48% maternal milk alone) without vitamin D supplementation. Most common clinical presentation in infants under 6 months was: hypocalcemic tetany/seizures; in children aged 6-12 months: failure to thrive; and in children over 12 months: skeletal deformities. Weight and height expressed as z-score value at diagnosis was 0.67 and 0.91, respectively. CONCLUSIONS: Nutritional rickets is a current reality in Catalonia and it mainly affects immigrant infants and children from Sub-Saharan Africa and Morocco, black or dark-skinned, fed with maternal milk alone, without vitamin D supplementation and with little sun exposure. Systematic, preventive supplementation with vitamin D is essential in these populations.

Age Distribution↗

Rickets.

Rickets, once thought vanquished, is reappearing. In some less developed countries it hardly went away. This seminar reviews the effects of genes, stage of development, and environment on clinical expression of the disease. Rickets can be secondary to disorders of the gut, pancreas, liver, kidney, or metabolism; however, it is mostly due to nutrient deficiency and we concentrate on this form. Although calcium deficiency contributes in communities where little cows' milk is consumed, deficiency of vitamin D is the main cause. There are three major problems: the promotion of exclusive breastfeeding for long periods without vitamin D supplementation, particularly for babies whose mothers are vitamin D deficient; reduced opportunities for production of the vitamin in the skin because of female modesty and fear of skin cancer; and the high prevalence of rickets in immigrant groups in more temperate regions. A safety net of extra dietary vitamin D should be re-emphasised, not only for children but also for pregnant women. The reason why many immigrant children in temperate zones have vitamin D deficiency is unclear. We speculate that in addition to differences in genetic factors, sun exposure, and skin pigmentation, iron deficiency may affect vitamin D handling in the skin or gut or its intermediary metabolism.

Adolescent↗

Plasma alkaline phosphatase activity: a screening test for rickets in preterm neonates.

Both rickets and raised plasma alkaline phosphatase activity are common in the preterm infant. Measurement of plasma alkaline phosphatase activity is valuable in screening for active disease and in diagnosis, but normal reference data are not available for preterm babies. In 30 consecutive preterm infants (birthweight 1580 +/- 410 g, gestational age 31 +/- 2.5 weeks) serial measurements of plasma alkaline phosphatase activity, plasma levels of calcium and inorganic phosphorus, and the pattern of alkaline phosphatase isoenzymes were made. Four patterns of changes in plasma alkaline phosphatase activity with time were seen. 4 of the 30 infants were shown to have rickets; these children and 14 of the 26 non-rachitic infants showed an increasing/peak/decreasing pattern with increasing age, but levels were much higher in the rachitic infants. The activity in all 30 was raised above the adult and childhood reference ranges at some point in time. The data suggest that an activity of five times the upper limit of the normal adult reference range is acceptable in the preterm infant but an activity higher than this may suggest rickets.

Alkaline Phosphatase↗

Parathyroid receptor gene expression by epiphyseal growth plates in rickets and tibial dyschondroplasia.

PTH/PTHrP receptor gene expression was evaluated in situ in avian epiphyseal growth plates taken from normal, rachitic and tibial dyschondroplasia (TD) afflicted chicks induced by thiram or by genetic selection. In the normal growth plates, PTH/PTHrP receptor gene expression was localized to the maturation zone as demonstrated by the expression of collagen type II (col II), osteopontin (OPN) genes and alkaline phosphatase activity (AP). In TD, either induced by thiram or by genetic selection, normal levels of PTH/PTHrP receptor gene expression were observed up to 21 days post-hatch. In rickets, on the other hand, no PTH/PTHrP receptor gene expression was observed in the growth plate from day 8 of a vitamin D-deficient diet. In cultured chondrocytes, PTH caused time-dependent down-regulation of its own receptor. These results suggest that alterations in the PTH/PTHrP receptor gene expression are associated with rickets but not with TD. The reduction in the PTH/PTHrP receptor gene expression in rickets may be due to the high plasma levels of PTH.

Animals↗

First place winner. Recurrent febrile seizures: an unusual presentation of nutritional rickets.

Nutritional rickets is a serious disease that is infrequently encountered in the United States today because of the fortification of infant formulas and dairy products with vitamin D. We report a case of undiagnosed nutritional rickets presenting with recurrent febrile seizures. Febrile seizures, a common and usually benign presenting complaint, are not among the symptoms generally known to be associated with rickets. Therefore, the disease was uncovered only after a careful history and physical examination prompted a more thorough investigation into an underlying cause for recurrent seizures. The diagnosis was subsequently confirmed by quantitative laboratory testing. We review the historical and cultural factors, symptoms, and physical findings suggestive of this potentially serious yet easily treatable disease.

Calcium Gluconate↗

Bone mineralization by OST-6 (OsteoCare), a herbomineral preparation, in experimentally induced rickets in rats.

In the present study the efficacy of OST-6 (OsteoCare), a herbomineral preparation, on bone mineralization in experimental rickets has been evaluated. This was accomplished by feeding pregnant rats and subsequently their pups with vitamin D and calcium deficient (VDCD) with low phosphorus diet. The parameters such as serum and bone mineral contents (calcium and inorganic phosphorus), serum alkaline phosphatase, sex hormones and histology of bone were considered. VDCD resulted in a significant reduction in bone and serum calcium and inorganic phosphorus, increased serum alkaline phosphatase and decreased sex hormones (testosterone in males, progesterone and oestrogen in females). Histologically the bone showed osteodystrophic changes and disproportionate cartilaginous proliferations in the epiphyseal region. Incorporation of OST-6 into feed at 5% concentration resulted in a complete reversal of rickets, which was substantiated by biochemical and histological observations. It has been concluded that OST-6 is useful in the management of rickets in a natural way through herbal resources.

Animals↗

Loss of DMP1 causes rickets and osteomalacia and identifies a role for osteocytes in mineral metabolism.

The osteocyte, a terminally differentiated cell comprising 90%-95% of all bone cells, may have multiple functions, including acting as a mechanosensor in bone (re)modeling. Dentin matrix protein 1 (encoded by DMP1) is highly expressed in osteocytes and, when deleted in mice, results in a hypomineralized bone phenotype. We investigated the potential for this gene not only to direct skeletal mineralization but also to regulate phosphate (P(i)) homeostasis. Both Dmp1-null mice and individuals with a newly identified disorder, autosomal recessive hypophosphatemic rickets, manifest rickets and osteomalacia with isolated renal phosphate-wasting associated with elevated fibroblast growth factor 23 (FGF23) levels and normocalciuria. Mutational analyses showed that autosomal recessive hypophosphatemic rickets family carried a mutation affecting the DMP1 start codon, and a second family carried a 7-bp deletion disrupting the highly conserved DMP1 C terminus. Mechanistic studies using Dmp1-null mice demonstrated that absence of DMP1 results in defective osteocyte maturation and increased FGF23 expression, leading to pathological changes in bone mineralization. Our findings suggest a bone-renal axis that is central to guiding proper mineral metabolism.

Adult↗

Studies of the porcine intestinal calcitriol receptor in pseudo-vitamin D deficiency rickets type I.

1. Calcitriol (1,25-dihydroxyvitamin D3) concentrations in plasma of humans and pigs with pseudo-vitamin D deficiency rickets type I (PVDRI) have been reported to be significantly lower than in normal subjects and animals. Sometimes, however, calcitriol concentrations are relatively high in these subjects and animals (50-80 pmol/l) and nevertheless clinical symptoms of rickets develop. We have studied whether or not the development of rachitic lesions in piglets with PVDRI is due to altered binding properties of the intestinal calcitriol receptor in addition to the defective renal production of calcitriol. PVDRI piglets with clinical and biochemical symptoms of rickets (hypocalcaemia, increased activity of alkaline phosphatase) and with calcitriol concentrations in plasma of 83.7 +/- 4.2 pmol/l (n = 7) were used. They were compared with unaffected piglets with normal calcitriol concentrations (178.0 +/- 17.7 pmol/l, n = 9). 2. The equilibrium dissociation constant (Kd) of the receptor in the PVDRI piglets (0.31 +/- 0.05 nmol/l) and in control piglets (0.33 +/- 0.05 nmol/l) and the maximum binding capacity (Bmax.) (674 +/- 103 and 719 +/- 122 fmol/mg of protein, respectively) were not different (n = 9). 3. The association rate constant (kass) at 4 degrees C [0.15 x 10(7) and 0.24 x 10(7) (mol/l)-1 min-1] and the dissociation rate constant (kdiss) (0.40 x 10(-3) and 0.48 x 10(-3) min-1; half-life of dissociation = 24.1 and 28.9 h, respectively) were also not different between diseased and control piglets.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗

Static and dynamic bone changes in hospitalized patients suffering from rickets--a histomorphometric study.

AIMS: The aim of this study was to assess static and dynamic bone changes in patients suffering from rickets. METHODS AND RESULTS: Transcortical iliac crest biopsies of 15 hospitalized children with rickets were taken after labelling new bone formation with two cycles of tetracycline administration 10 days apart. Undecalcified sections were prepared, appropriately stained and histomorphometric analysis performed. Static and dynamic bone changes were measured including the volume of bone and osteoid, trabecular and cortical bone dimensions and resorptive and mineralization activities. The results were compared with normal values. The nature of the mineralization fronts was noted. Trabecular osteoid volumes of all but one patient was above the normal range of 1.9% (+/-0.4%). This patient suffered rickets associated with the Kwashiorkor-Marasmus syndrome. Tetracycline labelling was found to be more sensitive than subjective evaluation of the nature of the mineralization fronts. Despite a balanced hospital diet, a bone formation rate of zero was found in three cases, indicating a need for vitamin D and mineral supplementation. Seven cases had decreased mineralization lag times, indicating response to the balanced diet. CONCLUSIONS: This study showed that histometric analysis of labelled bone biopsies is a helpful adjunct to the diagnosis but particularly assessment of response to management of deficiency states in children.

Adolescent↗

Hypophosphatemia leads to rickets by impairing caspase-mediated apoptosis of hypertrophic chondrocytes.

Rickets is seen in association with vitamin D deficiency and in several genetic disorders associated with abnormal mineral ion homeostasis. Studies in vitamin D receptor (VDR)-null mice have demonstrated that expansion of the late hypertrophic chondrocyte layer, characteristic of rickets, is secondary to impaired apoptosis of these cells. The observation that normalization of mineral ion homeostasis in the VDR-null mice prevents rachitic changes suggests that rickets is secondary to hypocalcemia, hypophosphatemia, or hyperparathyroidism, rather than impaired VDR action. To determine which of these abnormalities is responsible for impaired chondrocyte apoptosis and subsequent rachitic changes, two additional models were examined: diet-induced hypophosphatemia/hypercalcemia and hypophosphatemia secondary to mutations in the Phex gene. The former model is associated with suppressed parathyroid hormone levels as a consequence of hypercalcemia. The latter model demonstrates normal calcium and parathyroid hormone levels, but 1,25-dihydroxyvitamin D levels that are inappropriately low for the degree of hypophosphatemia. Our studies demonstrate that normal phosphorus levels are required for growth plate maturation and implicate a critical role for phosphate-regulated apoptosis of hypertrophic chondrocytes via activation of the caspase-9-mediated mitochondrial pathway.

Animals↗

Targeted ablation of the vitamin D receptor: an animal model of vitamin D-dependent rickets type II with alopecia.

Vitamin D, the major steroid hormone that controls mineral ion homeostasis, exerts its actions through the vitamin D receptor (VDR). The VDR is expressed in many tissues, including several tissues not thought to play a role in mineral metabolism. Studies in kindreds with VDR mutations (vitamin D-dependent rickets type II, VDDR II) have demonstrated hypocalcemia, hyperparathyroidism, rickets, and osteomalacia. Alopecia, which is not a feature of vitamin D deficiency, is seen in some kindreds. We have generated a mouse model of VDDR II by targeted ablation of the second zinc finger of the VDR DNA-binding domain. Despite known expression of the VDR in fetal life, homozygous mice are phenotypically normal at birth and demonstrate normal survival at least until 6 months. They become hypocalcemic at 21 days of age, at which time their parathyroid hormone (PTH) levels begin to rise. Hyperparathyroidism is accompanied by an increase in the size of the parathyroid gland as well as an increase in PTH mRNA levels. Rickets and osteomalacia are seen by day 35; however, as early as day 15, there is an expansion in the zone of hypertrophic chondrocytes in the growth plate. In contrast to animals made vitamin D deficient by dietary means, and like some patients with VDDR II, these mice develop progressive alopecia from the age of 4 weeks.

Alopecia↗

Meat consumption reduces the risk of nutritional rickets and osteomalacia.

Endogenous vitamin D deficiency (low serum 25(OH)D3) is a necessary but insufficient requirement for the genesis of vitamin D-deficiency rickets and osteomalacia. The magnitude of the independent contributions of dietary factors to rachitic and osteomalacic risk remains uncertain. We reanalysed two weighed dietary surveys of sixty-two cases of rickets and osteomalacia and 113 normal women and children. The independent associations of four dietary variables (vitamin D, Ca, fibre and meat intakes) and daylight outdoor exposure with rachitic and osteomalacic relative risk were estimated by multivariate logistic regression. Meat and fibre intakes showed significant negative and positive associations respectively with rachitic and osteomalacic relative risk (RR; zero meat intake: RR 29.8 (95 % CI 4.96, 181), P<0.001; fibre intake: RR 1.53 (95 % CI 1.01, 2.32), P=0.043). The negative association of meat intakes with rachitic and osteomalacic relative risk was curvilinear; relative risk did not fall further at meat intakes above 60 g daily. Daylight outdoor exposure showed a significant negative association with combined relative risk (RR 0.33 (95 % CI 0.17, 0.66), P<0.001). Operation of the meat and fibre risk factors was related to sex, age and dietary pattern (omnivore/lactovegetarian), mainly determined by religious affiliation. The mechanism by which meat reduces rachitic and osteomalacic risk is uncertain and appears independent of revised estimates of meat vitamin D content. The meat content of the omnivore Western diet may explain its high degree of protection against nutritional rickets and osteomalacia from infancy to old age in the presence of endogenous vitamin D deficiency.

Adolescent↗

Vitamin-D-deficiency rickets in Kuwait: the prevalence of a preventable disease.

Two hundred and fifty children with clinical, biochemical and radiological evidence of vitamin-D-deficiency rickets were studied over a period of 5 years. Their ages ranged from 1 month to 2 years. Breastfed infants formed 63% of total cases. Intramuscular therapy with vitamin D in a dose of 600,000 IU, deep intramuscular, proved to be safe and effective. In contrast, oral vitamin D did not provide such satisfactory results, presumably owing to poor patient/parental compliance. This report reveals that vitamin-D-deficieny rickets is common in Kuwait in spite of abundant sunlight all through the year because children are wrapped up and kept indoors. Insufficient intake of vitamin D is another important factor in the pathogenesis of vitamin-D-deficiency rickets in Kuwait.

Child, Preschool↗

Familial hypophosphataemic rickets: experience with 24 children from Kuwait.

Between 1982 and 1988, familial hypophosphataemic rickets (FHR) was diagnosed in 24 children, in nine during screening of the families of index patients. The average annual incidence was 0.2/1000 live births. There were 16 boys and 8 girls in 10 families, of which nine had more than one affected child. Their ages at the onset of the disease ranged between 10 months and 14 years (mean 6.9 yrs). Growth retardation and bowing of the legs were the most prominent features, observed in all index patients and in four of the patients diagnosed by screening. Treatment with 1 alpha-hydroxyvitamin D3 and phosphates was associated with acceleration of growth in all children, healing of rickets in 21, and normalization of the serum phosphate in 22. Two children with late diagnosis are now older than 16 years with a final height below the 3rd centile. Three more pubertal children are also shorter than the 3rd centile. In areas where nutritional rickets is common, FHR is likely to be missed and the treatment delayed with grave consequences; in particular, growth retardation and bone deformity.

Adolescent↗

Nutritional rickets in Calabar, Nigeria.

The features of 20 cases of nutritional rickets who presented at the University of Calabar Teaching Hospital, Calabar in south-eastern Nigeria over a 9-year period (January 1985-December 1993) are presented. The aim is to compare them with those in the only other reports from Nigeria between 18 and 42 years ago from Ibadan in the west of the country. The ages at presentation ranged between 6 months and 5 years with no sex preponderance. Most of the children were well nourished with the major features being delay in walking, swollen wrists and ankles and genu varum. The majority of cases in the present study occurred among children of elite and middle class parents who deprived their children of sunshine by keeping them indoors most of the day while they were at work. Reasons for the comparatively low prevalence of rickets in Calabar are social and cultural factors which enhance the exposure of children to sunlight. In addition, the relative availability of seafood and vegetables in this coastal city enhances rickets prevention.

Child, Preschool↗

Congenital rickets due to maternal vitamin D deficiency in a sunny island of Greece.

UNLABELLED: A full-term male infant presented with clinical and biochemical findings consistent with the diagnosis of congenital rickets: weak muscle tone, craniotabes, episodes of tremor, hypocalcaemia, elevated serum alkaline phosphatase, secondary hyperparathyroidism, decreased 25-hydroxyvitamin D and normal 1,25-dihydroxyvitamin D serum levels. The mother's history and biochemical findings suggested nutritional vitamin D deficiency. Treatment with calcium and vitamin D resulted in the disappearance of clinical findings of rickets, normalization of the baby's biochemical profile and normal growth. It is surprising that this case occurred in an affluent setting, in the Mediterranean island of Crete, with an abundance of sunlight throughout the year. CONCLUSION: We report this case in order to emphasize the continuing occurrence of congenital rickets even in populations not considered at risk for hypovitaminosis D. A high index of suspicion is required for prompt diagnosis and treatment, thus preventing complications.

Female↗

SLC34A3 mutations in patients with hereditary hypophosphatemic rickets with hypercalciuria predict a key role for the sodium-phosphate cotransporter NaPi-IIc in maintaining phosphate homeostasis.

Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is a rare disorder of autosomal recessive inheritance that was first described in a large consanguineous Bedouin kindred. HHRH is characterized by the presence of hypophosphatemia secondary to renal phosphate wasting, radiographic and/or histological evidence of rickets, limb deformities, muscle weakness, and bone pain. HHRH is distinct from other forms of hypophosphatemic rickets in that affected individuals present with hypercalciuria due to increased serum 1,25-dihydroxyvitamin D levels and increased intestinal calcium absorption. We performed a genomewide linkage scan combined with homozygosity mapping, using genomic DNA from a large consanguineous Bedouin kindred that included 10 patients who received the diagnosis of HHRH. The disease mapped to a 1.6-Mbp region on chromosome 9q34, which contains SLC34A3, the gene encoding the renal sodium-phosphate cotransporter NaP(i)-IIc. Nucleotide sequence analysis revealed a homozygous single-nucleotide deletion (c.228delC) in this candidate gene in all individuals affected by HHRH. This mutation is predicted to truncate the NaP(i)-IIc protein in the first membrane-spanning domain and thus likely results in a complete loss of function of this protein in individuals homozygous for c.228delC. In addition, compound heterozygous missense and deletion mutations were found in three additional unrelated HHRH kindreds, which supports the conclusion that this disease is caused by SLC34A3 mutations affecting both alleles. Individuals of the investigated kindreds who were heterozygous for a SLC34A3 mutation frequently showed hypercalciuria, often in association with mild hypophosphatemia and/or elevations in 1,25-dihydroxyvitamin D levels. We conclude that NaP(i)-IIc has a key role in the regulation of phosphate homeostasis.

Adolescent↗