Diagnostik und Therapie der hypophosphatämischen Rachitis im Kindesalter

Zusammenfassung

Die Rachitis im Kindes- und Jugendalter beruht auf einer Unterversorgung des wachsenden Körpers mit Kalzium und/oder Phosphat. Der Kalzium-Phosphat-Stoffwechsel unterliegt einer komplexen hormonellen Regulation durch Calcitriol, Parathormon und dem ‚Fibroblast Growth Factor 23‘(FGF23).

Eine unphysiologische Überproduktion von FGF23 führt durch resultierenden renalen Phosphatverlust zu einem Phosphatmangel, mit der Folge der Untermineralisation von Knochen, Zähnen und Wachstumsfugen und damit zur hypophosphatämischen Rachitis (HR) bzw. Osteomalazie. Die häufigste Form der FGF23-abhängigen HR ist die X-chromosomale hypophosphatämische Rachitis (XLH). Im Kindesalter steht, neben einer Substitution von Phosphat und aktivem Vitamin D, mit Burosumab seit 2018 ein monoklonaler Antikörper gegen FGF23 für die Therapie der XLH zur Verfügung. Diese Therapie hat das Potenzial, Langzeitkomplikationsraten, Wachstum und Lebensqualität substanziell zu verbessern, entsprechende Langzeitdaten werden daher in Registern gesammelt.

Möglichkeiten zur Vernetzung mit Betroffenen bieten die Vereine Phosphatdiabetes e.V. und www.phosphatdiabetes.at.

Abstract

Rickets is caused by an undersupply of calcium and/or phosphate to the growing body. The calcium-phosphate metabolism is regulated by the secosteroid hormone calcitriol, parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23).

Excessive FGF23 action results in reduced renal phosphate reabsorption, and subsequent hypophosphataemia, undermineralization of bone, teeth and growth plates and the phenotype of hypophosphatemic rickets (HR)/osteomalacia. The most common form of FGF23-dependent HR is X-linked hypophosphatemic rickets (XLH), which was traditionally treated via supplementation of phosphate and active vitamin D only. Since 2018, a monoclonal antibody against FGF23, Burosumab, is available for the therapy of XLH in children. The new therapy has the potential to improve long-term complications, growth and quality of life; such data are currently being collected in registries. Support groups for German-speaking people affected by XLHinclude Phosphatdiabetes e.V. and www.phosphatdiabetes.at.

Schlüsselwörter

Phosphat-Stoffwechsel - FGF23 - Hypophosphatämische Rachitis - Phosphatdiabetes - Osteomalazie, Burosumab

Key words

Phosphate metabolism - FGF23 - hypophosphatemic rickets - burosumab

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