O-14 A rare case of hypercalcaemia in pregnancy

Abstract Introduction Hypercalcaemia is infrequent during pregnancy, but it is associated with foetal and maternal morbidity and mortality. Although primary hyperparathyroidism (pHPT) accounts for the majority of the cases, other aetiologies such as genetic causes in a young population should be considered. Clinical Case A 27-year-old female was diagnosed with pHPT during her 16th week of gestation after she presented with vomiting and was found to have raised adjusted calcium of 3.22 mmol/L, low phosphate of 0.6 mmol/L and Parathyroid Hormone of 10.6 pmol/L. The patient's hypercalcaemia dated back 2 years, she had a history of three previous miscarriages, and was not on any hypercalcaemia-inducing medications. Unbeknownst to her, her father was also being evaluated for hypercalcaemia. Her thyroid-stimulating hormone was fully suppressed with raised free thyroid hormones and negative TSH receptor antibodies; this was improved with Carbimazole therapy. Plasma and urine Metanephrines were normal, and neck ultrasound did not reveal any parathyroid lesions. She underwent parathyroidectomy three weeks later after a period of intravenous hydration. A 2 cm left superior parathyroid adenoma was excised, and the plasma calcium level promptly normalised. Genetic testing for familial hyperparathyroidism revealed an autosomal dominant heterozygous CDC73 variant, which is associated with Hyperparathyroidism-Jaw Tumour syndrome. The Clinical Genetics team is arranging genetic testing for her first-degree relatives. She delivered a live baby at 38 + 6 weeks of gestation via emergency caesarean section, performed for foetal hypoxia on cardiotocography, and genetic testing of the newborn child using umbilical cord blood was performed at the time of delivery. She will undergo regular screening for uterine, renal and jaw tumours (every 5 years), and is planned for 6-monthly calcium and parathyroid hormone tests. Conclusion Primary hyperparathyroidism is best treated with parathyroidectomy before pregnancy as the maternal and foetal complications increase according to the hypercalcaemia severity. During pregnancy, mild cases could be treated conservatively while parathyroidectomy is reserved for severe cases and is performed in the second trimester. Germline CDC73 analysis is recommended in young pHPT patients, and in this case revealed a pathological variant associated with Hyperparathyroidism-Jaw Tumour syndrome, familial isolated pHPT and parathyroid carcinoma.