X-linked hypophosphatemia caused by a deep intronic variant in PHEX identified by PCR-based RNA analysis of urine-derived cells.

X-linked hypophosphatemia (XLH) is caused by dominant inactivating mutations in the phosphate regulating endopeptidase homology, X-linked (PHEX), resulting in elevated fibroblast growth factor 23 (FGF23), hypophosphatemia, rickets and osteomalacia. PHEX variants are identified in approximately 85 % of individuals with XLH, which leaves a substantial proportion of patients with negative DNA-based genetic testing. Here we describe a 16-year-old male who had typical features of XLH on clinical and radiological examination. Genomic DNA sequencing of a hypophosphatemia gene panel did not reveal a pathogenic variant. We therefore obtained a urine sample, established cell cultures and obtained PHEX cDNA from urine-derived cells. Sequencing of exon-spanning PCR products demonstrated the presence of an 84 bp pseudoexon in PHEX intron 21 due to a deep intronic variant (c.2147+1197A>G), which created a new splice donor site in intron 21. The corresponding PHEX protein would lack 33 amino acids on the C-terminus and instead include an unrelated sequence of 17 amino acids. The patient and his affected mother both had this variant. This report highlights that individuals with the typical clinical characteristics of XLH and negative genomic DNA sequence analysis can have deep intronic PHEX variants that are detectable by PCR-based RNA diagnostics.

Screening, assessment and management of type 2 diabetes mellitus in children and adolescents: Australasian Paediatric Endocrine Group guidelines.

INTRODUCTION: The incidence of type 2 diabetes mellitus has increased in children and adolescents due largely to the obesity epidemic, particularly in high risk ethnic groups. ß-Cell function declines faster and diabetes complications develop earlier in paediatric type 2 diabetes compared with adult-onset type 2 diabetes. There are no consensus guidelines in Australasia for assessment and management of type 2 diabetes in paediatric populations and health professionals have had to refer to adult guidelines. Recent international paediatric guidelines did not address adaptations to care for patients from Indigenous backgrounds. MAIN RECOMMENDATIONS: This guideline provides advice on paediatric type 2 diabetes in relation to screening, diagnosis, diabetes education, monitoring including targets, multicomponent healthy lifestyle, pharmacotherapy, assessment and management of complications and comorbidities, and transition. There is also a dedicated section on considerations of care for children and adolescents from Indigenous background in Australia and New Zealand. CHANGES IN MANAGEMENT AS A RESULT OF THE GUIDELINES: Published international guidelines currently exist, but the challenges and specifics to care for children and adolescents with type 2 diabetes which should apply to Australasia have not been addressed to date. These include: recommendations regarding care of children and adolescents from Indigenous backgrounds in Australia and New Zealand including screening and management; tighter diabetes targets (glycated haemoglobin, ≤ 48 mmol/mol [≤ 6.5%]) for all children and adolescents; considering the use of newer medications approved for adults with type 2 diabetes under the guidance of a paediatric endocrinologist; and the need to transition adolescents with type 2 diabetes to a diabetes multidisciplinary care team including an adult endocrinologist for their ongoing care.