Endocrine Abstracts

Williams-Beuren syndrome (WBS) is a rare multisystem genetic disorder, with an estimated prevalence of 1:7500 live births. WBS is characterised by distinctive facies, mild intellectual disability, cardiovascular disease, and endocrine disorders including hypothyroidism, hypercalcaemia, and diabetes. Hypercalcaemia is seen in 5 to 50% of individuals with WBS. It is usually identified in infancy and resolves during childhood. The first case report of WBS with primary hyperparathyroidism (PHPT) was published in 2017. Our report describes a patient with PHPT, where the diagnosis of WBS was established on genetic testing undertaken as part of the workup for PHPT. A 35-year-old gentleman has a history of mild intellectual disability and type 2 diabetes. He is investigated for persistently elevated serum calcium levels. The tests report an elevated parathyroid hormone level and a sestamibi scan is positive for a left inferior parathyroid adenoma. His Z score is less than -2. He undergoes a parathyroidectomy of the isolated gland and the histology is consistent with a parathyroid adenoma. He has been normocalcaemic one year postoperatively. He underwent genetic testing, which reported a heterozygous deletion of the long arm of chromosome 7, as seen in WBS. A review of his notes highlighted that WBS was suspected in infancy by a paediatrician and paediatric cardiologist, given his distinctive facies, hyperactivity, and presence of a cardiac murmur, but genetic testing was not performed at that time. The mechanism of hypercalcaemia with WBS is not fully understood. Various mechanisms have been proposed, including the potential role of transient receptor potential C3 (TRPC3) channels in increasing calcium absorption. The American Academy of Paediatrics recommends that patients with WBS have 2-yearly calcium checks from age 6, and more frequently at younger ages. Hypercalcaemia in individuals with WBS should be investigated, to ensure that alternative aetiologies are diagnosed and managed appropriately.