Debilitating Pain and Fractures: a Rare Case of Hypophosphatemic Osteomalacia with Concomitant Vitamin D Deficiency in Neurofibromatosis Type 1

Abstract

Hypophosphatemic osteomalacia is a rare form of metabolic bone disorder in neurofibromatosis type 1 (NF1). The exact disease mechanism of this disorder in NF1 is yet to be established. We present a 44-year-old female known to have NF1, who presents with debilitating bone pain, weakness and multiple fractures. Laboratory investigations showed persistent hypophosphatemia with renal phosphate wasting suggestive of hypophosphatemic osteomalacia. She also had concomitant vitamin D deficiency which contributed to the disease severity. Medical therapy with oral phosphate and vitamin D improved her symptoms without significant changes in fracture healing or phosphate levels.

Keywords: FGF23; NF1; Vitamin D deficiency; hypophosphatemia; osteomalacia.