Endocrine Abstracts

Introduction: We present a case of severe hypocalcaemia in a 6-week-old baby, secondary to genetic hypoparathyroidism.

Case report: A 6-week-old female presented with seizures. She is the first child to non-consanguineous parents of Asian-Pakistani ethnic origin. She was delivered at term and had an uneventful neonatal period. There was no family history of calcium disorders. Blood investigations showed low serum adjusted calcium of 1.26 mmol/l (2.2-2.6 mmol/l), low ionised calcium (0.65nmol/l), elevated inorganic phosphate 3.70 mmol/l (1.3-2.5 mmol/l). Further evaluation for hypocalcaemia showed low serum parathormone (PTH) 0.2 pmol/l (1.6-7.2 pmol/l). Vitamin D levels were sufficient, 57.4nmol/l (50-150). Spot urine calcium:creatinine ratio was 0.92. Serum magnesium was normal 0.72 mmol/l (0.7-1). Renal USS was normal. Genetics were sent to evaluate the cause of hypoparathyroidism and showed autosomal recessive GCM2 related hypoparathyroidism.

Management challenges: Intravenous calcium gluconate boluses only marginally improved the ionised calcium; hence she was started on continuous calcium infusion and alfacalcidol. In view of ongoing seizures, she was intubated and ventilated. EEG showed ongoing electrical seizure activity even in the absence of clinical seizures. MRI brain was normal. Adjusted calcium improved to 1.71- 1.94mmo/l (ionised calcium 0.83 – 0.94). Alfacalcidol doses were optimised to 150ng/kg/day. The high phosphate and low calcium remained challenging, and as she transitioned onto oral medication, she was commenced on calcium carbonate, which doubles as a phosphate binder, requiring doses up to 10 mmol/kg/day, given in 3-hourly divided doses. She was also placed on a high calcium milk feed. Adjusted calcium levels have remained static at around 1.9nmol/ls, however there are no clinical seizures, and the child is clinically well. Therefore, a clinical decision has been taken to accept the lower serum levels of calcium. There is a robust rescue plan for emergency attendances to ED, and for times of illness. Discussions are on-going for pre-emptive central i.v. access as well in case of emergencies.

Conclusion: GCM2 is a parathyroid-specific transcription factor and inactivating germline mutations (found on chromosome 6p24.2) can result in profound hypoparathyroidism. Resultant hypocalcaemia can be very challenging to manage, requiring tertiary and often multidisciplinary team input.