Management of perinatal HPP during critical illness/ECMO.

OBJECTIVES: With the advent of asfotase alfa, the enzyme replacement therapy (ERT) approved for hypophosphatasia (HPP), health care providers need to navigate management of ERT during critical illness.

CASE PRESENTATION: We present the case of a young girl, treated with ERT for severe perinatal HPP, who had cardiorespiratory arrest in the setting of influenza A. Her life-saving treatment involving extra corporeal membrane oxygenation (ECMO) required a two-week interruption of ERT leading to persistent hypercalcemia and hyperphosphatemia. A three year old female presented with respiratory distress and blood tinged secretions. She was influenza A positive with bilateral opacities on chest X-ray (CXR). Worsening respiratory distress and bradycardic arrest required intubation, CPR and venoarterial ECMO cannulation. She remained on ECMO for 10 days with anticoagulation restrictions requiring her thrice-weekly subcutaneous ERT to be held. Hypercalcemia (12.3 mg/dL) and hyperphosphatemia (7.6 mg/dL) developed two weeks after restarting ERT and resolved six weeks later.

CONCLUSIONS: We highlight that the obligatory cessation of ERT while on ECMO led to the loss of functional TNSALP with a profound decrease in bone mineralization leading to excess circulating calcium and phosphorus. In cases where it is necessary to interrupt ERT, we advise close monitoring of calcium and phosphorous levels.