Fibroblast growth factor 23 levels in cord and peripheral blood during early neonatal period as possible predictors of affected offspring of X-linked hypophosphatemic rickets: report of three female cases from two pedigrees.

OBJECTIVES: The role of serum fibroblast growth factor 23 (FGF23) level in early neonatal period on the diagnosis of X-linked hypophosphatemic rickets (XLH) remains unclear. CASE PRESENTATION: Two female patients from the first pedigree had an affected mother, and the other female from the second pedigree had an affected father. In all three cases, FGF23 levels were high in cord blood and peripheral blood at day 4-5. Additionally, the FGF23 levels considerably increased from birth to day 4-5. We identified a PHEX pathogenic variant and initiated treatment during infancy in each case. CONCLUSIONS: In neonates with a parent diagnosed as PHEX-associated XLH, FGF23 in cord blood and peripheral blood at day 4-5 may be useful markers for predicting the presence of XLH.

A novel C-terminal truncating NR5A1 mutation in dizygotic twins.

Nuclear receptor subfamily 5, group A, member 1 (NR5A1) is a nuclear receptor involved in gonadal and adrenal development. We identified a novel C-terminally truncating NR5A1 mutation, p.Leu423Trpfs*7, in dizygotic twins with 46,XY disorders of sex development. Our results highlight the functional importance of C-terminal region of NR5A1 and indicate that NR5A1 mutations can be associated with intrafamilial phenotypic variations, progressive testicular dysfunction, hypogonadotropic hypogonadism, and borderline adrenal dysfunction.