Growth in children with X-linked hypophosphataemic rickets

Currently, X-linked hypophosphataemic rickets (XLHR) is most commonly treated with a combination of phosphate and vitamin D, but there is conflicting evidence about the effects of this treatment on linear growth. In all, 25 patients with XLHR (current age range, 4.1–22.1 years; median, 8.2 years) were studied to determine whether there was any improvement in height SDS during treatment. The duration of therapy was 2.9–15.0 years (median, 5.7 years). Measurements before the age of 2 years or after the onset of puberty were excluded to remove the effects of measurement difficulties in small infants and of variation in pubertal timing. The growth of these patients was compared with a similar group of untreated historical controls. Patients treated with calcitriol and phosphate for at least 2 years before the onset of puberty (n = 22) had a significantly better mean height SDS than the historical controls (-1.23 compared with —2.05 for the historical controls; p = 0.02). Among patients treated with calcitriol and phosphate for at least 2 years (n = 21), the change in height SDS had a positive correlation with the duration of therapy ( r = 0.51; p = 0.02). The growth of children with XLHR treated with combination therapy was thus significantly better than that of historical controls.     

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

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. Received: 11 February 1998 / Accepted in revised form: 31 May 1998     

Metacarpal measurements in X-linked hypophosphataemic rickets

In 15 girls and 7 boys with hypophosphataemic vitamin D-resistant rickets, midshaft diameter, combined cortical thickness, cortical area and metacarpal length were determined in the second metacarpal on radiographs of the left hand. The values obtained were compared with age-matched and height-matched controls. In a longitudinal study the same bone measurements were taken in these 22 patients and in additional 3 boys. The metacarpal diameter in the patients was increased whereas the combined cortical thickness was decreased. The former feature appeared to have its onset in early childhood. Cortical area was normal for age and increased for height, which was taken to indicate a normal or increased bone mass in these children. Metacarpal length was normal for age and height in the boys and increased for height but still within the normal range in girls. This is in agreement with the normal arm-span that has been found in these children.     

Growth in X-linked hypophosphatemic rickets

Growth failure appears frequently in children with X-linked hypophosphatemic rickets (XLHR) due to hypophosphatemia, disease severity, body disproportion, and primary bone abnormality. Recombinant human growth hormone (rhGH) increases phosphate tubular reabsorption and phosphate level in blood and, thus, constitutes an attractive but controversial therapy in short children with XLHR, those efficacy was demonstrated in small uncontrolled series. Our aim was to report our experience regarding growth in XLHR. Twenty-seven children with XLHR—20 girls, seven boys—diagnosed at a median (md) of 1.46 years of age, (range 0.39–8.5 years), were studied at 10.12 years of age (1.58–18.56), md (range). All received oral treatment with phosphate and calcitriol. At the first visit, grouped Z-height was −1; (−4.58; 0.54) md (range). After 5 years’ follow-up (0.92–15.6), Z-height was −0.91 (− 4.56; 0.17), not different from that at baseline (P = 0.465). In 16 children entirely controlled in our program upon presentation, a “catch up” phenomenon after the rickets had healed (P = 0.823) or throughout the long-term was not observed (P = 0.995). Eight patients had a Z-height ≤ −2SD at the last visit, and impaired linear growth was associated with age >2 years at diagnosis, male gender and non-adherence to treatment. Four children, all boys, received rhGH, and in two cases with sufficient follow up stature normalized. No rhGH side effects were observed, and phosphate and calcitriol doses remained stable. Linear growth failure appeared in a third of XLHR children. Efforts need to be made to reduce the age of diagnosis and to improve adherence to treatment. Treatment with rhGH should be considered early, after the rickets has been controlled, in those patients with impaired growth or delayed diagnosis.     

Sagittal synostosis in X-linked hypophosphatemic rickets and related diseases

Background The recent observations of two new cases of X-linked hypophosphatemic rickets associated with premature closure of the sagittal suture prompted a review of similar cases seen in this institution. Objectives To review the clinical records and skull radiographs of 28 children with hypophosphatemic rickets in order to investigate the frequency and type of craniosynostosis and other cranial vault changes seen in these conditions and to review the literature for relevant findings. Materials and methods Clinical and imaging records were reviewed on 28 patients with hypophosphatemic rickets, all younger than 18 years. Most patients had X-linked hypophosphatemic rickets and a few had autosomal-dominant hypophosphatemic rickets or were non-familial cases. Results Of the 28 patients, 13 had sagittal synostosis. Dolichocephaly was present in ten patients. The configuration of the cranial vault in some of these ten patients with dolichocephaly varied somewhat from that seen in nonsyndromic sagittal synostosis. In one patient, a Chiari I malformation was demonstrated by MRI. In another patient with increased intracranial pressure the sagittal suture closure was associated with lambdoidal synostosis. Dolichocephaly was not present in three patients, suggesting that the synostosis started later than in the other patients, probably in the second year of life, a period of slower brain growth than in the first year. The two patients in this group of three showed thickening and sclerosis of the cranial vault of uncertain etiology. Conclusion There is an increased risk of sagittal synostosis in hypophosphatemic rickets and related diseases in children. The appearance of the cranial vault in this type of synostosis can vary from that seen in nonsyndromic synostosis. In this setting, careful clinical and imaging follow-up is warranted.     

X-连锁低磷性佝偻病的基因突变分析

目的：研究X-连锁低磷性佝偻病（XLH）患儿致病基因的突变频率和突变类型,探讨存在突变热点的可能性及基因型与临床表型的关系。方法：回顾性分析10例XLH患儿的临床资料,评估其基因突变类型及其与疾病严重程度之间的关系。结果：10例XLH患儿均检测到PHEX基因突变,其中6例为错义突变,2例为拼接位点突变,1例为框移突变,1例为无义突变。还发现了两个新突变,即c.2048T>C 和IVS14+1delAG。PHEX基因的突变类型与矮小程度、腿弯程度之间没有关联（分别P=0.571、0.467）;基因的突变位置与矮小程度、腿弯程度之间也没有关联（分别P=0.400、1.000）。结论：错义突变是XLH患儿最常见的突变类型;c.2048T>C 和IVS14+1delAG是PHEX基因的两个新突变。PHEX基因的突变类型和突变位置与疾病的严重程度无相关性。     

Growth hormone secretion in poorly growing children with renal hypophosphataemic rickets

We evaluated growth hormone (GH) secretion and baseline serum free insulin-like growth factor-I (IGF-I) levels in 12 poorly growing patients (5 males and 7 females; age 1.6–12.5 years, median 6.4) with renal hypophosphataemic rickets treated with 1,25-dihydroxy-vitamin D₃ plus inorganic oral phosphate salts. Eleven healthy normally growing children (6 males and 5 females age 3.1–10.8 years, median 6.6) were studied as control group. All patients had a normal GH response (GH peak 10 g/l) to at least one provocative pharmacological stimulus (levodopa or insulin tolerance test), as well as all the controls. Mean growth hormone concentrations (MGHC), mean pulse amplitude, number of GH peaks above 5 g/l, and IGF-I values overlapped between patients and controls, even though four patients had MGHC below the lower limit of MGHC of controls. In these patients, however, height-SDS, serum calcium, phosphate, alkaline phosphatase, intact parathyroid hormone, 1,25-dihydroxyvitamin D concentrations and maximum tubular phosphate reabsorption/glomerular filtration rate ratio did not differ in respect to the patients who showed MGHC in the range of controls (n = 6). MGHC, IGF-I and biochemical parameters of phospho-calcium metabolism did not differ when the patients were subdivided in two groups on the basis of the median (–2.4) of height-SDS. No relationship was found between MGHC or IGF-I and height-SDS or growth velocity-SDS. Height-SDS and years of treatment or age at which therapy was started were not related.     

X-连锁低磷性佝偻病的诊治进展

X-连锁低磷性佝偻病是最常见的遗传性佝偻病,临床亦不少见且容易误诊、漏诊,治疗与一般佝偻病相比更复杂.该文就X-连锁低磷性佝偻病的临床特征、致病基因以及治疗情况进行综述.     

Activity of renal 25-hydroxyvitamin D3-1α-hydroxylase in a case of X-linked hypophosphataemic rickets

In 1974, a 2-year-old boy was diagnosed as having X-linked hypophosphataemic rickets (XLH) because of severe rickets and hypophosphataemia.The vitamin D metabolite concentrations, blood and urine chemistry and renal 25-hydroxyvitamin D₃ (25 OHD₃)-1-hydroxlase were measured in 1982 (about 2 weeks after withdrawal of medication). 1-hydroxylase was 392 pg/mg tissue/20 min in the patient, which was high compared with aged-matched controls (69.7±28.5 pg/mg tissue/20 min, mean ±SD, n=7). Our present studies showed that the 1-hydroxylase activity in the patient with XLH was elevated. Therefore, the normal or low 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃) concentrations in XLH patients could be due to accelerated catabolism of 1,25-(OH)₂D₃ or abnormally regulated 25OHD₃-1-hydroxylase in response to hypophosphataemia, although significantly elevated above that in normal controls.Abbreviations XLH X-linked hypophosphataemic rickets - CPBA Competitive protein binding assay - Al-P alkaline phosphatase - P phosphate     

The pattern of growth and growth retardation of patients with hypophosphataemic vitamin D-resistant rickets: A longitudinal study

Growth in height of 16 patients (5 boys and 11 girls) with hypophosphataemic rickets (HR) was studied in a longitudinal survey. The data shortly before and during puberty were analysed on the basis of Preece Baines curves, fitted to the original data; for the analysis at the age of 5 years, the original data were used. It appeared that the overall shape of the individual and average growth pattern could be adequately described by the Preece Baines method. The results further showed that from the age of 5 years onwards, average height was approximately two standard deviations below the normal mean for Dutch children. The patients showed a normal pubertal growth spurt which was, in general, insufficient to restore the growth retardation already established before adolescence. The four children who did show catchup growth between the age of 5 years and adulthood had minimal rachitic lesions. The greater impact of the disease on growth in early childhood than on adolescent growth could be explained by the fact that HR mainly affects the growth of the legs, the major contributor to body size in early childhood. Finally, it was found that the difference between bone age, as determined by the Tanner Whitehouse (TW₂)-method, and chronological age was not significant and the adult height in all patients except two could be adequatcly predicted from bone age and height.     

Diagnosis of X-linked hypophosphatemia vitamin D resistant rickets

Recent advances in the pathophysiology and diagnosis of X-linked hypophosphatemic rickets (XLH) are reviewed. The recent discovery of the gene that is responsible for XLH especially enables us to understand the mechanism of hypophosphatemia in XLH. Laboratory and radiological findings are important for the diagnosis. However, dental abnormalities such as spontaneous dental abscess and a defect of dentin maturation are also notable findings.     

2例X-连锁低血磷性佝偻病患者PHEX基因新发突变的研究

目的研究2例X-连锁低血磷性佝偻病(XLH)患儿及家系磷酸盐调节基因(PHEX)的突变类型,以明确其遗传学病因。方法回顾性分析2例XLH患者临床资料,应用高通量测序技术从基因组水平对先证者的XLH致病基因PHEX进行检测,并应用PCR-Sanger测序法对突变基因的家系分布进行验证。结果 2例患儿均检测到PHEX基因新发突变,1例为移码突变c.931dupC,导致翻译提前终止,产生截短蛋白p.Gln311Profs*13;另1例为剪接位点突变IVS14+1GA,导致外显子15跳跃,产生不完整的氨基酸链。2例患儿父母的基因表型均正常。结论 c.931dup C和IVS14+1GA是PHEX基因的两个新突变,可能是XLH新的致病性突变。     

Epidermal naevus syndrome and hypophosphataemic rickets: description of a patient with central nervous system anomalies and review of the literature

The epidermal naevus syndrome (ENS) is a rare dermatological condition consisting of congenital epidermal nevi associated with anomalies in the central nervous system, bones, eyes, hear or genito-urinary system. We report a new case of ENS associated with hypophosphataemic rickets. The girl was born with a mixed-type epidermal naevus and skeletal anomalies. Hypophosphataemic rickets was diagnosed at the age of 2.5 years. At 14 years of age. MRI of the head demonstrated right brain hypotrophy, a left temporal arachnoid cyst and asymmetric lateral ventricles. We reviewed the literature and found 13 reported cases of ENS associated with hypophosphataemic rickets. Conclusion We report a further patient with epidermal naevus syndrome and hypophosphataemic rickets, followed from birth to the age of 15 years, who had structural central nervous system anomalies with normal intellectual functioning. A comprehensive neurological work up is recommended in patients with epidermal naevus syndrome.     

X连锁显性遗传性低磷血症性佝偻病诊治专家共识

X连锁显性遗传性低磷血症性佝偻病(OMIM307800)为罕见的遗传病,是低磷血症性佝偻病最常见的类型,患病率约为1/20 000^ [1],1937年由Albright等^ [2]首次报道。患者多在开始走路、骨骼逐渐负重后才被发现,如果不能及早、正确治疗,将导致骨骼残疾及生长障碍,严重损害患者及其家庭的生存质量,如果及早诊治,预后良好。     

Hypophosphatemic rickets : Easy to diagnose, difficult to treat

Hypophosphatemic rickets (HR) has generated a lot of interest in recent times. There is need to recognize this disorder and differentiate it from the more common nutritional rickets because the therapy is different. It is also important to emphasize that a detailed clinical examination with pedigree analysis and easily available biochemical tests are adequate to establish the diagnosis in most cases. This report presents three families with hypophosphatemic rickets. Interestingly, many of these patients had a mixed picture of HR and nutritional rickets. Their important features are described with special emphasis on early initiation of treatment with oral phosphate and stringent monitoring of renal functions to prevent development of irreversible renal insufficiency.     

Oral calcium treatment in vitamin D-dependent rickets type II

Vitamin D-dependent rickets type II is a rare hereditary disease that results from target organ resistance to the action of 1,25-dihydroxyvitamin D₃. There is a great heterogeneity in the clinical presentation of this condition. The affected patients usually present early in childhood with clinical and biochemical evidence of rickets. Physiological replacement dosage of 1,25-dihydroxyvitamin D₃ has no therapeutic effect. Responses to pharmacological doses of vitamin D metabolites or long-term calcium infusion have been variable. A case is reported here of an 8 year old girl, of consanguineous parents with vitamin D-dependent rickets, type II, in whom treatment with high dose oral calcium resulted in marked biochemical and radiological improvement. It is concluded that high dose oral calcium treatment is an effective treatment option for patients with vitamin D-dependent rickets type II.