Fibroblast growth factor 23 (FGF23) plays a crucial role in renal phosphate regulation, exemplified by the causal role of PHEX and DMP1 mutations in X-linked hypophosphatemic rickets and autosomal recessive rickets type 1, respectively. Using whole exome sequencing we identified compound heterozygous mutations in family with sequence similarity 20, member C (FAM20C) in two siblings referred for hypophosphatemia and severe dental demineralization disease. FAM20C mutations were not found in other undiagnosed probands of a national Norwegian population of familial hypophosphatemia. Our results demonstrate that mutations in FAM20C provide a putative new mechanism in human subjects leading to dysregulated FGF23 levels, hypophosphatemia, hyperphosphaturia, dental anomalies, intracerebral calcifications and osteosclerosis of the long bones in the absence of rickets. ß

ObjectiveDistance from residence location to a centre for renal replacement therapy (RRT) may influence patients’ quality of life and prognosis. Northern Norway constitutes 45% of Norway's landmass, but has less than 10% of the population.MethodsIn this study, we analysed all patients in northern Norway consecutively registered in the Norwegian Renal Registry during 2000–2012. A total of 634 patients (Nordland County 321 patients, Troms County 215 patients and Finnmark County 98 patients) were investigated.ResultsThere were more smokers (31% vs. 22%) and patients with diabetes (32% vs. 22%) in Finnmark, but the difference did not reach statistical significance. Patients undergoing RRT and living in Finnmark County had a significantly worse outcome (P=0.03). The median survivals after initiation of RRT were 3.8 years (Finnmark), 6.4 years (Troms) and 5.4 years (Nordland), respectively. The most common causes of death were cardiovascular disease (53%), infections (16%), withdrawal from therapy (15%) and malignancy (13%). In a Cox analysis, age (P<0.0001), diabetes (P=0.008) and smoking at any time (P<0.004) were individual factors correlated with inferior prognosis.ConclusionAge, smoking and diabetes were prognostic factors. Residents of the northernmost county (Finnmark) experienced an inferior prognosis. Long distance from residence location to hospital may be another factor, but this could not be documented. Preventive strategies should be improved.

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