Two Cases of Iron-Induced Hypophosphatemia

Present 2 cases of severe hypophosphatemia related to ferric carboxymaltose infusions with a brief overview of the pathophysiology and factors that predispose certain patients to this phenomenon.

A 46-year-old male with history of hereditary hemorrhagic telangiectasias presented with severe progressive bilateral foot and leg pain as well as insufficiency fractures after initiating on ferric carboxymaltose infusions. Biochemical evaluation demonstrated severe hypophosphatemia and renal phosphate wasting. Discontinuation of further iron infusions led to resolution of symptoms and improvement in phosphate levels.Similarly, a 61-year-old male with history of Crohn disease and prior bowel resections was identified to have consistent hypophosphatemia after ferric carboxymaltose infusions.

Hypophosphatemic disorders due to renal phosphate wasting present a diagnostic challenge and morbidity to patients further exacerbated by delays in diagnosis and treatment. Intravenous iron infusions are commonly used to treat a variety of medical conditions. These treatments, especially ferric carboxymaltose, can cause severe FGF23 mediated renal phosphate wasting and osteomalacia.

It is crucial for clinicians to recognize FGF23 mediated renal phosphate wasting in the setting of intravenous iron infusions. Patients with gastrointestinal malabsorption and secondary hyperparathyroidism can have sustained hypophosphatemia as a result of ferric carboxymaltose infusions.