In:
Hormone Research in Paediatrics, S. Karger AG, Vol. 71, No. 4 ( 2009), p. 237-244
Abstract:
〈 i 〉 Background: 〈 /i 〉 We report monozygotic twin girls with a family history consistent with X-linked hypophosphataemic rickets (XLH). One twin had a skeletal and biochemical phenotype consistent with XLH, whilst the second twin appeared normal. Complete non-penetrance in XLH has not been previously reported and our aim was to explore potential reasons for this. 〈 i 〉 Methods: 〈 /i 〉 Serum and urine biochemistry were analysed at regular intervals. Microsatellite analysis was performed to confirm monozygosity and bi-parental inheritance of the X chromosome. The X chromosome inactivation pattern was studied in peripheral blood. Exons of the paternal 〈 i 〉 PHEX 〈 /i 〉 and 〈 i 〉 FGF23 〈 /i 〉 genes were sequenced. 〈 i 〉 Results: 〈 /i 〉 Biochemistry was persistently abnormal in the slow-growing twin 1 and normal in twin 2 who has grown normally. Maximal tubular phosphate reabsorption was 0.68 mmol/l in twin 1 and 1.64 mmol/l in twin 2 at 10.8 years of age (normal 1.15–2.58 mmol/l). Microsatellite analysis confirmed monozygosity and the X chromosome inactivation pattern was random. These studies also excluded uniparental isodisomy. The exon sequence of paternal 〈 i 〉 PHEX 〈 /i 〉 and 〈 i 〉 FGF23 〈 /i 〉 genes was normal. 〈 i 〉 Conclusions: 〈 /i 〉 Discordant X inactivation is a well-recognised phenomenon in identical twins, and we suspect that non-random expression of the normal 〈 i 〉 PHEX 〈 /i 〉 gene in critical tissues is the most likely explanation for non-penetrance.
Type of Medium:
Online Resource
ISSN:
1663-2818
,
1663-2826
Language:
English
Publisher:
S. Karger AG
Publication Date:
2009
detail.hit.zdb_id:
2540224-9
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