Activating calcium sensor receptor (CaSR) mutations often present with hypocalcemia and hypomagnesemia. Severe hypocalcemia with this mutation has been reported but severe hypomagnesemia has not been well described.
Aim: To identify the cause of severe hypocalcemia and hypomagnesemia in a young child, and explore the efficacy of continuous subcutaneous magnesium therapy as a safer alternative to intravenous magnesium.
Patient: A 2-8/12 year-old female with severe hypocalcemia and hypomagnesemia of unknown etiology.
Methods: Genetic analysis was performed on the proband and both parents. The proband was treated with human parathyroid hormone (teriparatide) and a continuous infusion of subcutaneous magnesium sulfate initially using a Deltec insulin pump and subsequently a Curlin infusion pump.
Results: The patient has a known de novo mutation in the CASR gene (A843E). She could not be adequately managed with enteral and intravenous electrolyte replacement even after adding teriparatide. She responded well to adjunctive therapy with continuous subcutaneous magnesium.
Conclusions: Severe hypomagnesemia can be part of the phenotype of activating CaSR mutations. Subcutaneous magnesium should be considered in patients with difficult to control hypomagnesemia.