Dr Ting chia Lew1, Dr Sridevi Govindarajulu1, Dr Jerry Dong1, Dr Hayley Walker1, Dr Janice Krishna1
1Toowoomba Hospital, Toowoomba , Australia
Biography:
Dr Lew is the current Renal Advanced Trainee in Toowoomba Hospital, with special interest in dialysis and kidney supportive care.
Dr Lew is committed to providing longitudinal care to her patients from the early days in the disease course to the final days with targeted patient-centred treatment plan.
Background:
Hypophosphatemia is a known complication associated with ferric carboxymaltose (Ferinject) infusion secondary to its effect on FGF23. Despite it being highly utilised in iron deficiency anaemia, the risk of hypophosphatemia has not been routinely discussed in daily practice, including in patients with chronic renal disease who has higher tendency to receive iron infusion than general population.
Case Report:
We present a case of 79-year-old women with background of chronic kidney disease stage III who presented to the hospital for bilateral feet pain, functional decline, and atrial fibrillation with rapid ventricular response. Initial investigations showed severe hypophosphatemia of 0.29 mmol/L and mild hypocalcaemia of 1.94 mmol/L. She received 1000 mg of Ferinject infusion a month prior to presentation. Further workup revealed elevated parathyroid hormone level of 56 pmol/L, FGF-23 of 176.5 ng/L , 1,25-dihydroxyvitamin D of 37 pmol/L, urine calcium creatinine ratio 0.014, urine phosphate creatinine ratio 0.55, normal urine amino acid. The investigations findings were in keeping with renal wasting of phosphate as the aetiology of her severe hypophosphatemia in correspondence to the phosphaturic effect of elevated FGF23 from Ferinject infusion.
Conclusion:
Severe hypophosphatemia can be a clinically significant adverse effect from Ferinject infusion by inhibiting cleavage of active FGF23 into its inactive component, leading to hypophosphatemia, hypocalcaemia, hyperphosphaturia, hyperparathyroidism, hypocalcitriolemia. This complication should be more widely discussed and acknowledged by practitioner prior to prescribing the medication, especially in the population with chronic kidney disease who routinely being screened and dosed with intravenous iron replacement. This seemingly benign treatment may come with a price to pay ,and close monitoring of electrolytes post infusion should be considered to minimise the risk of unwanted outcome.