Vitamin D-dependent Rickets Type Research Articles

Rickets with Alopecia Signals Vitamin D Dependent Rickets Type II

Vitamin D-dependent rickets type II is a rare autosomal recessive disorder. We report 27 months female child with classical rachitic changes, very high level of 25-hydroxy Vitamin D, 1,25 (OH)2D and markedly elevated serum Alkaline phosphatase. Very high dose of oral calcium and vitamin D3 was prescribed with minor improvement in skeletal features and alopecia. This case report hints the physician to diagnose and manage Vitamin D-dependent rickets type II, when rachitic changes are associated with alopecia.J Nepal Paediatr Soc 2015;35(2):198-201

Novel CYP27B1 Gene Mutations in Patients with Vitamin D-Dependent Rickets Type 1A.

The CYP27B1 gene encodes 25-hydroxyvitamin D-1α-hydroxylase. Mutations of this gene cause vitamin D-dependent rickets type 1A (VDDR-IA, OMIM 264700), which is a rare autosomal recessive disorder. To investigate CYP27B1 mutations, we studied 8 patients from 7 unrelated families. All coding exons and intron-exon boundaries of CYP27B1 gene were amplified by PCR from peripheral leukocyte DNA and subsequently sequenced. Homozygous mutations in the CYP27B1 gene were found in all the patients and heterozygous mutations were present in their normal parents. One novel single nucleotide variation (SNV, c.1215 T>C, p.R379R in the last nucleotide of exon 7) and three novel mutations were identified:, a splice donor site mutation (c.1215+2T>A) in intron 7, a 16-bp deletion in exon 6 (c.1022-1037del16), and a 2-bp deletion in exon 5 (c.934_935delAC). Both c.1215 T>C and c.1215+2T>A were present together in homozygous form in two unrelated patients, and caused exon 7 skipping. However, c.1215 T>C alone has no effect on pre-mRNA splicing. The skipping of exon 7 resulted in a shift of downstream reading frame and a premature stop codon 57 amino acids from L380 (p.L380Afs*57). The intra-exon deletions of c.1022-1037del16 and c.934_935delAC also resulted in a frameshift and the creation of premature stop codons at p.T341Rfs*5, and p.T312Rfs*19, respectively, leading to the functional inactivation of the CYP27B1 gene. Clinically, all the patients required continued calcitriol treatment and the clinical presentations were consistent with the complete loss of vitamin D1α-hydroxylase activity. In conclusion, three novel mutations have been identified. All of them caused frameshift and truncated proteins. The silent c.1215 T>C SNV has no effect on pre-mRNA splicing and it is likely a novel SNP. The current study further expands the CYP27B1 mutation spectrum.

A novel compound mutation of CYP27B1 in a Chinese family with vitamin D-dependent rickets type 1A

Mutations in the CYP27B1 gene, which encodes vitamin D 1α-hydroxylase, are the genetic basis of vitamin D-dependent rickets type 1A (VDDR1A, MIM 264700). The aim of this study was to investigate a novel CYP27B1 mutation and its clinical manifestations. VDDR1A was diagnosed based on clinical presentation, a physical examination, bone characteristics on an X-ray, and laboratory results. A molecular model of the CYP27B1 protein was constructed using the SWISS-MODEL server and Swiss-PdbViewer. We sequenced the CYP27B1 gene in a 5-year-old male child who presented with growth retardation and a history of frequent hand, leg, and perioral twitching since the age of 12 months. We identified a compound heterozygous mutation consisting of two missense mutations: one in exon 7 (R389C [c.1165C>T]) and one in exon 8 (R459C [c.1375C>T]). We used the wild-type CYP27B1 as a receptor and calcidiol as a ligand to predict the interaction between the R459 site and calcidiol. According to the predicted structure, the wild-type R459 residue localizes to the pocket where CYP27B1 binds to its ligand. According to the Human Gene Mutation Database, the compound heterozygous mutation identified in our patient is novel and has not yet been reported in the literature. This mutation provides a new basis for further research on VDDR1A and for the development of clinical diagnostics.

Vitamin D receptor mutations in patients with hereditary 1,25-dihydroxyvitamin D-resistant rickets

ContextHereditary vitamin D resistant rickets (HVDRR), also known as vitamin D-dependent rickets type II, is an autosomal recessive disorder characterized by the early onset of rickets with hypocalcemia, secondary hyperparathyroidism and hypophosphatemia and is caused by mutations in the vitamin D receptor (VDR) gene. The human gene encoding the VDR is located on chromosome 12 and comprises eight coding exons and seven introns. Objectives, patients, and methodsWe analyzed the VDR gene of 5 previously unreported patients, two from Singapore and one each from Macedonia (former Yugoslav Republic), Saudi Arabia and Turkey. Each patient had clinical and radiographic features of rickets, hypocalcemia, and the 4 cases that had the measurement showed elevated serum concentrations of 1,25-dihydroxyvitamin D (1,25(OH)2D). Mutations were re-created in the WT VDR cDNA and examined for 1,25(OH)2D3-mediated transactivation in COS-7 monkey kidney cells. ResultsDirect sequencing identified four novel mutations and two previously described mutations in the VDR gene. The novel mutations included a missense mutation in exon 3 causing the amino acid change C60W; a missense mutation in exon 4 causing the amino acid change D144N; a missense mutation in exon 7 causing the amino acid change N276Y; and a 2bp deletion in exon 3 5′-splice site (IVS3∆+4–5) leading to a premature stop. ConclusionsThese 4 unique mutations add to the previous 45 mutations identified in the VDR gene in patients with HVDRR.

Updates on rickets and osteomalacia: vitamin D dependency

Vitamin D dependency was first termed for patients resembling vitamin D-deficiency but require high doses of vitamin D administration. Now this disease is known to be caused by defective conversion of 25OHD to 1,25 (OH) 2D, which is termed vitamin D-dependent rickets type 1 or 1α-hydroxylase deficiency, or by end-organ unresponsiveness to 1,25 (OH) 2D, which is called vitamin D-dependent rickets type 2 or hereditary vitamin D-resistant rickets. Recent advance in the molecular analysis of these diseases revealed variety in the presentation and in the inheritance patterns. Molecular diagnosis would be preferable for some atypical cases for adequate therapy.

Vitamin D dependent rickets type 1 (VDDR-1): two years after discontinuation of treatment

Vitamin D dependent rickets type 1 (VDDR-1): two years after discontinuation of treatment

Vitamin D Dependent Rickets Type II with Alopecia

As a test of the effects of age and information load Ss performed a visual and auditory discrimination task under conditions requiring division of attention. Amount of stimulus information was determined by the number of stimulus alternatives which could occur in a set of trials. Performance by 12 Ss over age 40 was impaired in comparison to 12Ss under age 40. Performance for all Ss was a function of amount of information, but there was no Age X Information Load interaction. It has been reported in the literature that age-related performance decrements are correlated with task complexity. These data indicate that amount of information is not a critical dimension of task complexity as it contributes to age-related performance deficits.

No evidence for a role of rare CYP27B1 functional variations in multiple sclerosis

Association studies have implicated common variants in the 12q14.1 region containing CYP27B1 in multiple sclerosis (MS). Rare CYP27B1 mutations cause autosomal recessive vitamin D-dependent rickets type 1, and it has recently been reported that heterozygous CYP27B1 mutations are associated with increased MS susceptibility and lower active vitamin D levels. By sequencing CYP27B1 in 134 multiplex families and genotyping the most common variant R389H in 2,608 MS patients and 1,987 controls from Italy and Belgium (a total of 4,729 individuals), we were unable to replicate these observations. These results provide evidence against a major role for CYP27B1 mutations in MS.

No evidence of association between mutant alleles of the CYP27B1 gene and multiple sclerosis

An association has previously been reported between susceptibility to multiple sclerosis and the rare mutant alleles of the CYP27B1 gene responsible for autosomal recessive vitamin D–dependent rickets type 1 (VDDR1). In an attempt to replicate this finding, we screened 495 multiplex families and 2,092 single affected families, together with 4,594 cases and 3,583 controls (a total of 17,073 individuals) but were unable to find any evidence supporting this putative association. Our data do not indicate that mutations responsible for VDDR1 influence the risk of developing multiple sclerosis. ANN NEUROL 2013;73:430–432

ビタミンD依存性くる病II型の歯科的問題について:臨床的,X線学的ならびに組織学的分析

ビタミンD依存性くる病II型の歯科的問題について:臨床的,X線学的ならびに組織学的分析

Clinical and genetic analysis of patients with vitamin D‐dependent rickets type 1A

Vitamin D-dependent rickets type 1A (VDDR-IA, OMIM 264700) is a rare autosomal recessive disorder and is caused by mutations in the CYP27B1 gene. We aim to investigate CYP27B1 mutation in seven patients from four separate families and characterize the genotype-phenotype correlation. The entire coding region of the CYP27B1 gene was sequenced, and genotype-phenotype correlation among patients was assessed. Sequencing analysis identified biallelic CYP27B1 mutations in all patients and monoallelic mutations in their parents. One patient from the first family was compound heterozygous for c.1166G>A (p.Arg389His) and a novel nonsense mutation c.1079 C>A (p.Ser360*). Two patients from the second family were homozygous for a novel splice donor site mutation in intron 1 (c.195+2 T>G), causing partial retention of the intron and a shift in the reading frame. Both novel mutations lead to the complete loss of vitamin D1α-hydroxylase activity. Four patients from families 3 and 4 were homozygous for a previously reported duplication mutation in exon 8 (1319-1325dupCCCACCC, Phe443Profs*24). Interestingly, one patient who was presented with severe hypocalcaemia and seizures at 4months of age as a result of Phe443Profs*24 has improved spontaneously since 11years of age and does not need regular treatment. Her laboratory tests showed normal serum calcium and 1,25(OH)(2) D after refusing to take medication for 12months. There is a good genotype-phenotype correlation in VDDR-IA. However, some patients may recover from the loss of CYP27B1 function, probably due to 1α-hydroxylase activity exerted by a non-CYP27B1 enzyme.

A novel CYP27B1 mutation causes a feline vitamin D-dependent rickets type IA

A 12-week-old domestic cat presented at a local veterinary clinic with hypocalcemia and skeletal abnormalities suggestive of rickets. Osteomalacia (rickets) is a disease caused by impaired bone mineralization leading to an increased prevalence of fractures and deformity. Described in a variety of species, rickets is most commonly caused by vitamin D or calcium deficiencies owing to both environmental and or genetic abnormalities. Vitamin D-dependent rickets type 1A (VDDR-1A) is a result of the enzymatic pathway defect caused by mutations in the 25-hydroxyvitamin D(3)-1-alpha-hydroxylase gene [cytochrome P27 B1 (CYP27B1)]. Calcitriol, the active form of vitamin D(3), regulates calcium homeostasis, which requires sufficient dietary calcium availability and correct hormonal function for proper bone growth and maintenance. Patient calcitriol concentrations were low while calcidiol levels were normal suggestive of VDDR-1A. The entire DNA coding sequencing of CYP27B1 was evaluated. The affected cat was wild type for previously identified VDDR-1A causative mutations. However, six novel mutations were identified, one of which was a nonsense mutation at G637T in exon 4. The exon 4 G637T nonsense mutation results in a premature protein truncation, changing a glutamic acid to a stop codon, E213X, likely causing the clinical presentation of rickets. The previously documented genetic mutation resulting in feline VDDR-1A rickets, as well as the case presented in this research, result from novel exon 4 CYP27B1 mutations, thus exon 4 should be the initial focus of future sequencing efforts.

Novel vitamin D 1α-hydroxylase gene mutations in a Chinese vitamin-D-dependent rickets type I patient

Hereditary rickets is classified into four types: X-linked hypophosphatemic vitamin-D-resistant rickets, autosomal dominant hypophosphatemic vitamin-D-resistant rickets, vitamin-D-dependent rickets type I, and vitamin-D-dependent rickets type II, and the genes responsible are PHEX, FGF23, CYP27B1 and VDR, respectively (Clausmeyer et al. 2009; Gribaa et al. 2010; Malloy et al. 2010). Vitamin-Ddependent rickets type I (VDDR-I, MIM 264700), also known as vitamin D 1α-hydroxylase deficiency or pseudovitamin D deficiency rickets, is a rare autosomal recessive disorder characterized by the early onset of rickets with hypocalcemia. VDDR-I is caused by mutations of the 25hydroxyvitamin D 1α-hydroxylase gene (CYP27B1, MIM 609506) (Wang et al. 1998; Kitanaka et al. 1998). We identified compound heterozygous mutations in CYP27B1 gene in a Chinese VDDR-I patient. Both mutations are novel and include a small 11 nucleotide deletion (c.311321delGGCCCGAGCGC, p.R104LfsX225) in exon 2 that alters the downstream reading frame and creates a premature TGA stop signal at codon 328, and a missense mutation (c.473T>C, p.L158P) in exon 3 causing the amino acid change L158P. This study confirms the relationship between mutations of the CYP27B1 gene and the clinical findings of vitamin-D-dependent rickets type I.

Vitamin D-Dependent Rickets Type 1: A Rare, but Treatable, Cause of Severe Hypotonia in Infancy

Vitamin D-dependent rickets type 1 is an autosomal recessive disorder caused by an inactivating mutation of the 25-hydroxyvitamin-D-1α-hydroxylase (CYP27B1) gene. Clinical presentation is characterized by early onset of severe rickets and can include severe hypotonia. Here, we report a 16-month-old white male who presented with severe muscle weakness, failure to thrive, renal tubular dysfunction, and skeletal deformities, including osteopenia and multiple fractures. At presentation, he had severe hypocalcemia, hypophosphatemia, hypomagnesemia, and elevated alkaline phosphatase and parathyroid hormone levels, although normal 25-hydroxyvitamin D levels. DNA sequencing of the CYP27B1 gene revealed a novel mutation in exon 2 (c286_300de115) and a previously reported mutation in exon 7 (c.1166G>A). Once calcitriol therapy was initiated, the patient showed significant improvement in muscle strength and linear growth. Serum calcium, phosphorous, and alkaline phosphatase returned to normal range. Organic aciduria resolved and aminoaciduria significantly improved 2 months after parathyroid hormone levels normalized.

Mutation prediction by PolyPhen or functional assay, a detailed comparison of CYP27B1 missense mutations

Vitamin D-dependent rickets type 1 (VDDR-I) is caused by mutation in CYP27B1. The glycine residue at codon 102 is not conserved between human (G(102)) and rodent (S(102)). G102E mutation results in 80% reduction in its enzymatic activity but PolyPhen predicts benign change. It is not known whether G102S has any damaging effect on 1α-hydroxylase activity. We investigated the effect of CYP27B1 (G102S) on its enzymatic activity and compared mutation prediction accuracy for all known CYP27B1 mutations among three free online protein prediction programs: PolyPhen, PolyPhen-2, and PSIPRED. G102S has no damaging effect on 1α-hydroxylase activity. G102D retained 30% enzymatic activity. All three programs correctly predicted damaging change for G102D. PolyPhen predicted benign change for G102S, whereas PolyPhen-2 and PSIPRED indicated possible damaging effect. Among 24 reported damaging mutations, PSIPRED, PolyPhen-2, and PolyPhen achieved 100%, 91.7% (22/24), and 75% (18/24) accuracy rate, respectively. The residues of incorrectly predicted mutations were not conserved. We conclude that G102D resulted in a significant reduction in 1α-hydroxylase activity, whereas G102S did not. PSIPRED and PolyPhen-2 are superior to PolyPhen in predicting damaging mutations.

Alopecia in vitamin D-dependent rickets type II responding to 1α-hydroxycholecalciferol

A 4-year-old boy presented with rickets, alopecia and macrocephaly along with elevated serum levels of 1,25(OH)₂D₃ which was diagnostic of vitamin D-dependent rickets type II. The rickets responded to conventional doses of 1α-hydroxycholecalciferol together with oral calcium supplement and there was also improvement in the alopecia. In patients with vitamin D-dependent rickets type II with alopecia, although rickets improves with treatment, improvement in alopecia has not been reported before.

A Novel G102E Mutation of CYP27B1 in a Large Family with Vitamin D-Dependent Rickets Type 1

Mutations in the CYP27B1 gene, which encodes vitamin D 1alpha-hydroxylase, are the genetic basis for vitamin D-dependent rickets type 1 (VDDR-I). The aim of this study was to investigate the CYP27B1 mutation in a large family with VDDR-I and characterize the genotype-phenotype correlation. The index patient was a 23-yr-old female who had a progressive form of rickets and growth retardation since the age of 9 months. Laboratory data showed hypocalcemia, low urine calcium, hypophosphatemia, high serum alkaline phosphatase, elevated PTH, and low serum 1,25-dihydroxyvitamin D(3). Her parents were healthy first-degree cousins, and two of her 12 siblings were affected with similar but milder rickets. Three other siblings were asymptomatic but had biochemical evidence of the disease. The entire coding region of the CYP27B1 gene was sequenced, and the mutation was characterized by functional studies. We found a novel biallelic c.305G>A sequence variation at codon 102, changing amino acid from glycine to glutamic acid (G102E) in the patient and five affected siblings, whereas a monoallelic c.305G>A variation was present in the mother and five nonaffected siblings. This variation was not present in 100 population controls. Expression of this mutant in CHO cells revealed an 80% reduction in the 1alpha-hydroxylase activity as compared to wild-type activity. A novel mutation in the CYP27B1 gene was found in patients with VDDR-I. This mutation resulted in a significant reduction in 1alpha-hydroxylase activity. The residual enzymatic activity may account for the mild phenotype presentation in some affected members.

Presence of a Deletion Mutation (c.716delA) in the Ligand Binding Domain of the Vitamin D Receptor in an Indian Patient with Vitamin D-Dependent Rickets Type II

Vitamin D-dependent rickets type II (VDDR-type II) is a rare disorder caused by mutations in the vitamin D receptor (VDR) gene. Here, we describe a patient with VDDR-type II with severe alopecia and rickets. She had hypocalcemia, hypophosphatemia, secondary hyperparathyroidism, and elevated serum alkaline phosphatase and 1,25-dihydroxyvitamin D(3). Sequence analysis of the lymphocyte VDR cDNA revealed deletion mutation c.716delA. Sequence analysis of her genomic DNA fragment amplified from exon 6 of the VDR gene incorporating this mutation confirmed the presence of the mutation in homozygous form. This frameshift mutation in the ligand binding domain (LBD) resulted in premature termination (p.Lys240Argfs) of the VDR protein. The mutant protein contained 246 amino acids, with 239 normal amino acids at the N terminus, followed by seven changed amino acids resulting in complete loss of its LBD. The mutant VDR protein showed evidence of 50% reduced binding with VDR response elements on electrophoretic mobility assay in comparison to the wild-type VDR protein. She was treated with high-dose calcium infusion and oral phosphate. After 18 months of treatment, she gained 6 cm of height, serum calcium and phosphorus improved, alkaline phosphatase levels decreased, and intact PTH normalized. Radiologically, there were signs of healing of rickets. Her parents and one of her siblings had the same c.716delA mutation in heterozygous form. Despite the complete absence of LBD, the rickets showed signs of healing with intravenous calcium.

Hypocalcemia in Infants and Children

Hypocalcemia in Infants and Children

Vestibular dysfunction in vitamin D receptor mutant mice

The vitamin D endocrine system is essential for calcium and bone homeostasis. Vitamin D deficits are associated with muscle weakness and osteoporosis, whereas vitamin D supplementation may improve muscle function, body sway and frequency of falls, growth and mineral homeostasis of bones. The loss of muscle strength and mass, as well as deficits in bone formation, lead to poor balance. Poor balance is one of the main causes of falls, and may lead to dangerous injuries. Here we examine balance functions in vitamin D receptor deficient (VDR−/−) mice, an animal model of vitamin D-dependent rickets type II, and in 1α-hydroxylase deficient (1α-OHase−/−) mice, an animal model of pseudovitamin D-deficiency rickets. Recently developed methods (tilting box, rotating tube test), swim test, and modified accelerating rotarod protocol were used to examine whether the absence of functional VDR, or the lack of a key vitamin D-activating enzyme, could lead to mouse vestibular dysfunctions. Overall, VDR−/− mice, but not 1α-OHase−/− mice, showed shorter latency to fall from the rotarod, smaller fall angle in the tilting box test, and aberrant poor swimming. These data suggest that VDR deficiency in mice is associated with decreased balance function, and may be relevant to poorer balance/posture control in humans with low levels of vitamin D.