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Wang LKP, Shanmugasundaram M, Cooney E, Lee PDK. Siblings with vitamin D-dependent rickets type 1A: Importance of genetic testing and a review of genotype-phenotype correlations. Am J Med Genet A 2024:e63780. [PMID: 38822637 DOI: 10.1002/ajmg.a.63780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/09/2024] [Accepted: 05/18/2024] [Indexed: 06/03/2024]
Abstract
Vitamin D-dependent rickets type 1A (VDDR1A) is a rare condition caused by biallelic pathogenic variants in CYP27B1, which encodes 25-hydroxyvitamin D3-1-α-hydroxylase. Inadequate activity of this enzyme results in deficient 1α-hydroxylation of inactive 25-hydroxyvitamin D to biologically active 1,25-dihydroxyvitamin D, with consequent adverse effects on calcium and phosphate metabolism. A female child was clinically diagnosed at 18 months old with hypophosphatemic rickets based on phenotype and biochemical testing, with neither parent affected. A subsequent affected male sibling led to the reconsideration of the diagnosis. Exome sequencing showed a homozygous CYP27B1 c.1040T>A (p.Ile347Asn) variant for both children. No variants were found in genes associated with hypophosphatemic rickets. A review of published cases of VDDR1A with homozygous CYP27B1 variants indicates variable clinical presentation, lack of genotype-phenotype correlation, and low serum phosphate at diagnosis in most cases. These findings emphasize the clinical importance of molecular testing as part of the diagnostic evaluation for cases of non-nutritional rickets.
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Affiliation(s)
| | | | - Erin Cooney
- Department of Pediatrics, University of Texas Medical Branch, Galveston, Texas, USA
| | - Phillip D K Lee
- Department of Pediatrics, University of Texas Medical Branch, Galveston, Texas, USA
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Norlin M, Wikvall K. Enzymatic activation in vitamin D signaling - Past, present and future. Arch Biochem Biophys 2023; 742:109639. [PMID: 37196753 DOI: 10.1016/j.abb.2023.109639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 05/10/2023] [Accepted: 05/14/2023] [Indexed: 05/19/2023]
Abstract
Vitamin D signaling is important in regulating calcium homeostasis essential for bone health but also displays other functions in cells of several tissues. Disturbed vitamin D signaling is linked to a large number of diseases. The multiple cytochrome P450 (CYP) enzymes catalyzing the different hydroxylations in bioactivation of vitamin D3 are crucial for vitamin D signaling and function. This review is focused on the progress achieved in identification of the bioactivating enzymes and their genes in production of 1α,25-dihydroxyvitamin D3 and other active metabolites. Results obtained on species- and tissue-specific expression, catalytic reactions, substrate specificity, enzyme kinetics, and consequences of gene mutations are evaluated. Matters of incomplete understanding regarding the physiological roles of some vitamin D hydroxylases are critically discussed and the authors will give their view of the importance of each enzyme for vitamin D signaling. Roles of different vitamin D receptors and an alternative bioactivation pathway, leading to 20-hydroxylated vitamin D3 metabolites, are also discussed. Considerable progress has been achieved in knowledge of the vitamin D3 bioactivating enzymes. Nevertheless, several intriguing areas deserve further attention to understand the pleiotropic and diverse activities elicited by vitamin D signaling and the mechanisms of enzymatic activation necessary for vitamin D-induced responses.
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Affiliation(s)
- Maria Norlin
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden.
| | - Kjell Wikvall
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
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Lin Y, Guan Z, Mei H, Zhang W, Zhou Z, Su L, Cheng J, Zheng R, Liang C, Cai Y, Yin X, Wu D, Liu L, Zeng C. Clinical characteristics and long-term outcomes of 12 children with vitamin D-dependent rickets type 1A: A retrospective study. Front Pediatr 2022; 10:1007219. [PMID: 36405822 PMCID: PMC9671943 DOI: 10.3389/fped.2022.1007219] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 09/27/2022] [Indexed: 11/06/2022] Open
Abstract
PURPOSE Vitamin D-dependent rickets type 1A (VDDR1A) is a rare autosomal recessive disorder caused by deficiency of the CYP27B1 gene. This study aims to investigate the phenotypic and genotypic features of VDDR1A children in southern China and evaluate the long-term therapeutic effects. METHODS Twelve children from southern China with VDDR1A were enrolled in this study. Their clinical, radiological, biochemical, and molecular findings were analyzed retrospectively. The rickets severity score (RSS), biochemical parameters, and height standard deviation score (HtSDS) were used to evaluate clinical outcomes. RESULTS Six males and six females were included in this VDDR1A cohort. The age of onset was from 6 months to 1.8 years, and the age at diagnosis was 2.1 ± 0.8 years. The most common clinical symptoms at diagnosis were delayed walking (10/12) and severe growth retardation (9/12). HtSDS at diagnosis was negatively associated with age (p < 0.05). All patients presented with hypocalcemia, hypophosphatemia, increased serum alkaline phosphatase and parathyroid hormone, and high RSS at diagnosis. Two allelic variants of the CYP27B1 gene were identified in all patients, including nine different variants, four known and five novel, with c.1319_1325dupCCCACCC(p.Phe443Profs*24) being the most frequent. All patients were treated with calcitriol and calcium after diagnosis, and all patients but one were followed-up from 6 months to 15.6 years. HtSDS, RSS, and biochemical parameters were found to be improved during the first few years of the treatment. However, only five patients had good compliance. Although RSS and biochemical parameters were significantly improved, the HtSDS change was not significant from the time of diagnosis to the last visit, and seven patients remained of a short stature (HtSDS < -2). CONCLUSION Our study extends the mutational spectrum of VDDR1A and finds a hotspot variant of the CYP27B1 gene in southern China. The results reconfirm the importance of early diagnosis and treatment compliance and reveal the challenge of height improvement in VDDR1A patients.
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Affiliation(s)
- Yunting Lin
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Zhihong Guan
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Huifen Mei
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Wen Zhang
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Zhizi Zhou
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Ling Su
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Jing Cheng
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Ruidan Zheng
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Cuili Liang
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Yanna Cai
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Xi Yin
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Dongyan Wu
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Li Liu
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
| | - Chunhua Zeng
- Department of Genetics and Endocrinology, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangdong Provincial Clinical Research Center for Child Health, Guangzhou, China
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