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Hypophosphatemia Gene Panel Sponsored Program: A High Yield of Molecular Diagnoses from Clinically Confirmed XLH and Suspected Genetic Hypophosphatemia

X-linked hypophosphatemia (XLH), a dominant disorder caused by a disease-associated variant in the PHEX gene, affects males and females of all ages. Rickets and osteomalacia may be present along with short stature, lower limb deformity, muscle pain and/or weakness/fatigue, bone pain, joint pain/stif...

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Detalles Bibliográficos
Autores principales: Dahir, Kathryn, Rush, Eric, Beltran, Daniel, Eisenbeis, Scott, Johnson, Britt, Ramesan, Prameela, Sarafrazi, Soodabeh, Truty, Rebecca, Miller, Nicole
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8265956/
http://dx.doi.org/10.1210/jendso/bvab048.533
Descripción
Sumario:X-linked hypophosphatemia (XLH), a dominant disorder caused by a disease-associated variant in the PHEX gene, affects males and females of all ages. Rickets and osteomalacia may be present along with short stature, lower limb deformity, muscle pain and/or weakness/fatigue, bone pain, joint pain/stiffness, hearing difficulty, enthesopathy, osteoarthritis, and dental abscesses. Patients with XLH have below-normal serum phosphate and elevated serum FGF23. XLH is one of multiple etiologies of hypophosphatemia; depending on genetic cause, management may differ. Acquired hypophosphatemia (e.g. tumor induced osteomalacia) is non-hereditary in nature. This program provides a no-charge genetic test to confirm a clinical XLH diagnosis or to aid suspected genetic hypophosphatemia diagnosis. Patients aged >/= 6 months with either a clinical XLH diagnosis or suspicion of genetic hypophosphatemia, as evidenced by 2 or more clinical signs/ symptoms, were eligible for testing. The next generation sequencing panel includes 13 genes: ALPL, CLCN5, CYP2R1, CYP27B1, DMP1, ENPP1, FAH, FAM20C, FGF23, FGFR1, PHEX, SLC34A3 and VDR. Copy number variant detection was performed. 831 unrelated individuals were tested as of June 30, 2020. 569 (68.5%) of these subjects had a PHEX variant: 519 (91.2%) were either pathogenic or likely pathogenic (P/LP) and 50 (8.8%) were variants of uncertain significance (VUS). Of the 312 (37.5%) cases where no PHEX molecular diagnosis was found, 38 (12.2%) had molecular diagnoses associated with other genes/disorders: 4 had a variant (P/LP) in FGF23 (autosomal dominant [AD] hypophosphatemic rickets), 2 had two variants (P/LP) in CYP27B1 (autosomal recessive [AR] vitamin D dependent rickets), 1 had P/LP variants in ENPP1 (AR hypophosphatemic rickets Type 2). There were 27 cases with single P or LP variants in ALPL (AD hypophosphatasia, HPP); 4 cases carried two variants (P/LP) in ALPL (AR form). Of 237 unique P/LP PHEX variants detected: 59 were deletions, duplications or insertions; 37 were copy number variants; 52 were splice-site variants; 89 were single nucleotide variants. Additional family member testing/clinical information resulted in 48 cases having VUS reclassified to P/LP, highlighting the value of cascade family testing/clinical info to resolve VUS. RNA analyses to resolve VUS may further improve molecular diagnostic yield. Program results demonstrate a high diagnostic yield for XLH/ genetic hypophosphatemia and new insight into XLH-associated PHEX variants.