Genetic diagnosis of X-linked dominant hypophosphatemic rickets in a cohort study: Tubular reabsorption of phosphate and 1,25(OH)2D serum levels are associated with PHEX mutation type

<p>Abstract</p> <p>Background</p> <p>Genetic Hypophosphatemic Rickets (HR) is a group of diseases characterized by renal phosphate wasting with inappropriately low or normal 1,25-dihydroxyvitamin D₃(1,25(OH)₂D) serum levels. The most common form of HR is X-linked dominant HR (XLHR) which is caused by inactivating mutations in the <it>PHEX </it>gene. The purpose of this study was to perform genetic diagnosis in a cohort of patients with clinical diagnosis of HR, to perform genotype-phenotype correlations of those patients and to compare our data with other HR cohort studies.</p> <p>Methods</p> <p>Forty three affected individuals from 36 non related families were analyzed. For the genetic analysis, the <it>PHEX </it>gene was sequenced in all of the patients and in 13 cases the study was complemented by mRNA sequencing and Multiple Ligation Probe Assay. For the genotype-phenotype correlation study, the clinical and biochemical phenotype of the patients was compared with the type of mutation, which was grouped into clearly deleterious or likely causative, using the Mann-Whitney and Fisher's exact test.</p> <p>Results</p> <p>Mutations in the <it>PHEX </it>gene were identified in all the patients thus confirming an XLHR. Thirty four different mutations were found distributed throughout the gene with higher density at the 3' end. The majority of the mutations were novel (69.4%), most of them resulted in a truncated PHEX protein (83.3%) and were family specific (88.9%). Tubular reabsorption of phosphate (TRP) and 1,25(OH)₂D serum levels were significantly lower in patients carrying clearly deleterious mutations than in patients carrying likely causative ones (61.39 ± 19.76 vs. 80.14 ± 8.80%, p = 0.028 and 40.93 ± 30.73 vs. 78.46 ± 36.27 pg/ml, p = 0.013).</p> <p>Conclusions</p> <p><it>PHEX </it>gene mutations were found in all the HR cases analyzed, which was in contrast with other cohort studies. Patients with clearly deleterious <it>PHEX </it>mutations had lower TRP and 1,25(OH)₂D levels suggesting that the <it>PHEX </it>type of mutation might predict the XLHR phenotype severity.</p

Identifying important outcomes for young people with chronic kidney disease and their caregivers: a nominal group technique study

RATIONALE AND OBJECTIVE: Chronic kidney disease (CKD) has wide-ranging and long-term consequences for young people and their families. The omission of outcomes that are important to young people with CKD and their caregivers limits knowledge to guide shared decision-making. We aimed to identify the outcomes that are important to young people with CKD and their caregivers. STUDY DESIGN: We used the nominal group technique whereby participants identified and ranked outcomes and explained their priorities. SETTING AND PARTICIPANTS: Young people with CKD (stage 1-5, dialysis or transplant) and their caregivers were purposively sampled from six centers across Australia, the United States and Canada. ANALYTICAL APPROACH: Importance scores were calculated (scale of 0 to 1), and qualitative data were analyzed thematically. Results: Thirty-four patients (aged 8-21 years) and 62 caregivers participated in 16 groups, and identified 48 outcomes. The five highest ranked outcomes for patients were survival (importance score = 0.25), physical activity (0.24), fatigue (0.20), lifestyle restrictions (0.20) and growth (0.20), and for caregivers, kidney function (0.53), survival (0.28), infection (0.22), anemia (0.20) and growth (0.17). Twelve themes were identified reflecting their immediate and current priorities (wanting to feel normal, strengthening resilience, minimizing intrusion into daily life, imminent threats to life, devastating family burdens, and seeking control over health) and considerations regarding future impacts (protecting health/development, remaining hopeful, concern for limited opportunities, prognostic uncertainty, dreading painful and invasive procedures and managing expectations). LIMITATIONS: Only English-speaking participants were recruited. CONCLUSIONS: Kidney function, infection, survival and growth were the highest priorities for patients with CKD and their caregivers. Young people with CKD also prioritized highly the outcomes that directly affected their lifestyle and sense of normality, while caregiver’s highest priorities concerned the long-term health of their child, current health problems, and the financial and family burdens of caring for a child with CKD