Vitamin D-dependent Rickets Research Articles

CYP3A4 mutation causes vitamin D-dependent rickets type 3.

Genetic forms of vitamin D-dependent rickets (VDDRs) are due to mutations impairing activation of vitamin D or decreasing vitamin D receptor responsiveness. Here we describe two unrelated patients with early-onset rickets, reduced serum levels of the vitamin D metabolites 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, and deficient responsiveness to parent and activated forms of vitamin D. Neither patient had a mutation in any genes known to cause VDDR; however, using whole exome sequencing analysis, we identified a recurrent de novo missense mutation, c.902T>C (p.I301T), in CYP3A4 in both subjects that alters the conformation of substrate recognition site 4 (SRS-4). In vitro, the mutant CYP3A4 oxidized 1,25-dihydroxyvitamin D with 10-fold greater activity than WT CYP3A4 and 2-fold greater activity than CYP24A1, the principal inactivator of vitamin D metabolites. As CYP3A4 mutations have not previously been linked to rickets, these findings provide insight into vitamin D metabolism and demonstrate that accelerated inactivation of vitamin D metabolites represents a mechanism for vitamin D deficiency.

Rare, genetically conditioned forms of rickets: Differential diagnosis and advances in diagnostics and treatment.

Apart from the classic forms of rickets, there are rare genetic disorders from the group of vitamin D-resistant rickets where the clinical picture is very similar to the classic forms. Diagnosis of genetically conditioned rickets is often delayed. It is very important to know that a disorder of genetic background may be the cause of the failure of classic treatment in patients with rachitic symptoms. In the group of genetically conditioned rickets there are, among others, congenital hypophosphatemic rickets and vitamin D-dependent rickets type I and II. Congenital hypophosphatemic rickets is characterised by bone mineralisation disturbances related to hypophosphatemia secondary to renal loss of phosphates. The term "hypophosphatemic rickets" covers a group of diseases with similar phenotype but with different genotypes, inheritance models and etiopathogeneses. Mutation of at least 10 genes underlying this disease entity has been described. Vitamin D-dependent rickets are caused by defects of vitamin D metabolism. There are 4 forms described in literature that are distinguished by their genetic causes: type 1A (vitamin D-dependent rickets type IA), type 1B (vitamin D-dependent rickets type IB) and type 2A (vitamin D-dependent rickets type 2A), type 2B (vitamin D-dependent rickets type 2B). A detailed family history in combination with a physical examination, biochemistry and X-ray imaging helps in differential diagnostics of rare forms of rickets.

Rickets/Osteomalacia. Vitamin D dependency.

Vitamin D dependency is caused by inborn error in the process of vitamin D metabolism or action. It is classified to vitamin D-dependent rickets type 1 which shows defective 1,25(OH)2D production, and vitamin D-dependent rickets type 2 which shows end-organ unresponsiveness to 1,25(OH)2D. 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 adequate diagnosis and therapy.

Congenital atrichia with papular lesions: a rare cause of irreversible childhood alopecia

Congenital atrichia with papular lesions (APL) is a disease characterized by the complete absence of hair from the whole body occurring within a few months of birth and the presence of papules distributed over the body. A 9-year-old boy presented with sparse hair over his body and with a history of losing his hair soon after birth. Multiple skin-colored papules were observed over the scalp. A biopsy from a papule showed keratinous cysts in the dermis and the absence of hair follicles. A diagnosis of congenital APL was made after vitamin D-dependent rickets was excluded. This case highlights congenital APL as a cause of total alopecia.

WITHDRAWN: Clinical and genetic analysis of two Chinese families with vitamin D-dependent rickets type IA and follow-up.

Ahead of Print article withdrawn by publisher.

Genetic Causes of Rickets.

Rickets is a metabolic bone disease that develops as a result of inadequate mineralization of growing bone due to disruption of calcium, phosphorus and/or vitamin D metabolism. Nutritional rickets remains a significant child health problem in developing countries. In addition, several rare genetic causes of rickets have also been described, which can be divided into two groups. The first group consists of genetic disorders of vitamin D biosynthesis and action, such as vitamin D-dependent rickets type 1A (VDDR1A), vitamin D-dependent rickets type 1B (VDDR1B), vitamin D-dependent rickets type 2A (VDDR2A), and vitamin D-dependent rickets type 2B (VDDR2B). The second group involves genetic disorders of excessive renal phosphate loss (hereditary hypophosphatemic rickets) due to impairment in renal tubular phosphate reabsorption as a result of FGF23-related or FGF23-independent causes. In this review, we focus on clinical, laboratory and genetic characteristics of various types of hereditary rickets as well as differential diagnosis and treatment approaches.

Vitamin D-dependent rickets - a rare form of rickets - diagnostics and therapeutic problem

Searchable abstracts of presentations at key conferences on calcified tissues ISSN 2052-1219 (online)

Vitamin D-dependent rickets type 1 due to a novel mutation in CYP27B1

Searchable abstracts of presentations at key conferences on calcified tissues ISSN 2052-1219 (online)

Conservative management of metabolic derangements in osseous tissue among patients with vitamin d-dependent rickets type 2

Searchable abstracts of presentations at key conferences on calcified tissues ISSN 2052-1219 (online)

A novel mutation of CYP27B1 in two siblings with vitamin D-dependent rickets type 1A

A novel mutation of CYP27B1 in two siblings with vitamin D-dependent rickets type 1A

Late Onset of Vitamin D-Dependent Rickets Presenting with 8 years of Low Back Pain: A Case Report

Vitamin D (Vit D) is a prohormone that can be activated during a sequential hydroxylation done by two major mitochondrial cytochrome P450 liver and renal enzymes. Vit D-dependent rickets type 1 (VDDR1) is a rare autosomal recessive hereditary disorder resulting from defective renal 1α-OHase presenting with severe rickets, hypocalcemia, and secondary hyperparathyroidism. Although homozygous Vit D hydroxylation deficient patients develop severe rickets symptom and signs before the age of 12 months, heterozygous types have minor symptoms and are extremely rare presenting as late as 14 years after birthday. Here we present a suspicious case of VDDR1 at 21 years old of age with mild symptoms and signs.

High Dose Oral Calcium Treatment in Patients with Vitamin D-dependent Rickets Type II

High Dose Oral Calcium Treatment in Patients with Vitamin D-dependent Rickets Type II

A Case Report on Vitamin D-dependent Rickets Type 1 with Failure to Thrive and Regression of Motor Development

A Case Report on Vitamin D-dependent Rickets Type 1 with Failure to Thrive and Regression of Motor Development

Vitamin D-Dependent Rickets Type I caused by a Novel Frameshift Mutation of the 25-hydroxyvitamin D1-alpha-hydroxylase gene (CYP27B1)

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Transcriptional activation of the wild-type and mutant vitamin D receptors by vitamin D3 analogs.

The active form of vitamin D3 (1α,25(OH)2D3, also known as calcitriol) controls the expression of target genes via the vitamin D receptor (VDR). Vitamin D-dependent rickets type II (VDDRII) is a congenital disease caused by inactivating mutations in the VDR The condition is treated with high doses of calcitriol, but the therapeutic effects of other synthetic VD3 analogs have not yet been investigated. In the present study, we analyzed the transcriptional activity of seven different VD3 analogs with VDRs carrying ligand-binding domain mutations identified in VDDRII patients. Wild-type VDR (WT-VDR) and seven mutant VDRs were expressed in TSA201 human embryonic kidney cells, HepG2 human liver cancer cells, and MC3T3-E1 mouse calvaria cells, and their transcriptional activation with VD3 analogs were analyzed by performing transient expression assays, western blotting, and quantitative real-time PCR. The results demonstrated that falecalcitriol stimulated significantly higher transcriptional activation of the WT-VDR and some mutant VDRs than did calcitriol. Calcitriol showed almost no transcriptional activation of the VDR with the I268T mutation identified in a severe case of VDDRII, whereas falecalcitriol caused a dose-dependent increase in the activation of this mutant VDR. Our findings demonstrate that falecalcitriol has a VDR activation profile distinct from that of calcitriol and may exhibit therapeutic effects even on difficult-to-treat VDDRII cases resistant to calcitriol. It is also possible that VDDRII patients responding to high doses of calcitriol could be appropriately treated with low doses of falecalcitriol.

Genotype and Phenotype Characteristics in 22 Patients with Vitamin D-Dependent Rickets Type I

Background and Aims: Vitamin D-dependent rickets type I (VDDR1) is an autosomal recessive disorder caused by mutations in the 25-hydroxyvitamin D 1-alpha-hydroxylase gene (CYP27B1). Mutations in CYP27B1 disrupt or lead to a total loss of the 1-α-hydroxylase activity and require treatment with physiological doses of calcitriol. Patients and Methods: A genetic analysis of the CYP27B1 gene was conducted in 22 Turkish patients with VDDR1 from 13 families. Presenting characteristics, biochemical features, treatment, and results from the genetic analysis are described. Results: A splice donor site mutation c.195 + 2T>G was found in 10 patients. The novel missense p.192K>E (c.574A>G) mutation was detected in 5 patients, and a novel missense p.197G>D (c.590G>A) mutation was found in 4 patients. A previously reported 7-bp duplication 1319-1325dupCCCACCC (Phe443Profs*24) in exon 8 was detected in 1 patient, and 1 patient was a compound heterozygote for the novel p.192K>E and the previously described 1319-1325dupCCCACCC mutations. A novel single base pair deletion, c.171_171delG, leading to a frameshift, was found in 1 patient. Conclusions: We identified 3 novel and 2 previously described mutations in the CYP27B1 gene. A marked phenotypical diversity was observed between families that carried identical mutations, suggesting phenotypical heterogeneity.

Vitamin D dependency and its treatment

Vitamin D dependency is classified to vitamin D-dependent rickets type 1 which shows defective 1,25(OH)(2)D production, and vitamin D-dependent rickets type 2 which shows end-organ unresponsiveness to 1,25(OH)(2)D. 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 adequate therapy especially in type 2.

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

Vitamin D-Dependent Rickets: Eight cases

Objective: Vitamin D is essential for bone development and health, and deficiency resulting in rickets and skeletal defor mities is seen mainly during rapid growth. Hereditary vitamin D dependent rickets type I and type II rickets is a very rare form of rickets, characterized by 1-alpha-hydroxylase defi ciency or end-organ resistance to vitamin D. We aimed to investigate, clinical and laboratory characteristics of eight cases with Vitamin D-dependent rickets (VDRR). Method: The mean age of patients during diagnosis was 2.6 years. Excluding one patient, others were males (87.5%). Results: Mean laboratory values during referral was calcium 7.5±1,5 mg/dl, phosphorus 4±1.2 mg/dl, alkaline phosphatase (ALP) 1679±641 U/L and parathyroid hormone (PTH) 524±498 pg/ml. Patients received 1.2 µg/kg/day calcitriol. During follow-ups serum ALP and PTH values of patients turned to normal levels. Conclusion: In rickets, cases with persistent increased serum ALP and PTH levels it will be appropriate to investigate serum 25 (OH) D levels in cases diagnosed with vitamin D-dependent rickets even though hypocalcaemia is absent. Administration of adequate doses of calcitriol in some cases is able to clinical and laboratory values return to normal.

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.