Hypophosphatemic rickets: a nationwide, prospective, observational registry

Ariadne Bosman, Bram van der Eerden, Carola Zillikens on behalf of the Bone Network from the Dutch Society of Endocrinology

Erasmus MC, Department of Internal Medicine

Background: Phosphate is critical for skeletal development and mineral metabolism. Absorption occurs in the small intestine and excretion takes place in urine and feces. PTH, 1,25-dihydroxyvitamin D and FGF23 are the major regulators of phosphate homeostasis. A phosphate deficiency leads to e.g. muscle weakness and rickets/osteomalacia. Several inherited and acquired causes of phosphate renal wasting lead to hypophosphatemic rickets (HR). X linked hypophosphatemia (XLH) is the most common form with a prevalence of 1:20.000. Acquired causes are e.g. tumor induced osteomalacia (TIO). The prevalence of chronic hypophosphatemia in the Netherlands and the clinical manifestations are not clear.

Objective: To identify and evaluate patients with XLH and other forms of chronic hypophosphatemia, in a registry in the Netherlands.

Methods: To include patients in the registry, endocrinologist and nephrologists will be approached. All patients with chronic hypophosphatemia, are eligible. After informed consent, a chart review will be performed to collect data on initial presentation, symptoms, radiological, genetic and laboratory examination, treatment and follow up. The registry will be updated every 12 months.

Results: We expect that the data collected in this registry will lead to more insight in the prevalence, natural history, treatment and its effects on HR and into genotype-phenotype relations in the different genetic forms.

Conclusion: Within the Bone Network from the Dutch Society of Endocrinology a nationwide registry will be set up for genetic and acquired forms of chronic hypophosphatemia which will lead to improved insight in prevalence, causes, disease manifestations and therapy of this rare metabolic bone disease.