TITLE:
Hypophosphatemic Nephrolithiasis/Osteoporosis Type 1 Phenotype—A Novel Npt2a-Encoding SLC34A1 Mutation: A Case Report
AUTHORS:
Reyner Loza, Leonardo Vergara Valverde, Fernando Arias, Víctor Neyra Chagua
KEYWORDS:
Hypophosphatemic Rickets Type 1, Genu Varum, NPT2A
JOURNAL NAME:
Open Journal of Nephrology,
Vol.16 No.3,
August
10,
2026
ABSTRACT: We report the case of a 15-year-old female patient presenting with bone deformity characterized by genu varum in the lower extremities since the age of five, with a clinical diagnosis of X-linked hypophosphatemic rickets (XLHR). Laboratory tests revealed hypophosphatemia and a tubular reabsorption of phosphate (TRP) rate of 46 %. The patient was treated with 250 mg of oral potassium phosphate (Kphos)® and 0.25 µg of calcitriol twice daily. Genetic testing to confirm the XLHR diagnosis identified a heterozygous mutation (c.1315_1316delAG) in the SLC34A1 gene, causing arginine substitution at codon 439 with glycine and a frameshift, leading to a premature stop (p. Arg439Glyfs*165). This rare, previously unreported variant is consistent with a hypophosphatemic nephrolithiasis/osteoporosis type 1 (NPHLOP1) phenotype-associated autosomal dominant inheritance pattern. The girl’s progress is favorable; she continues treatment with phosphorus supplements and has also received orthopedic treatment, and she has not developed nephrolithiasis to date.