Endocrine Abstracts

We present a 3-month-old boy who was born at term, to non-consanguineous parents by spontaneous vaginal delivery, weighing 4.19 kg. Newborn examination, including eyes, was normal. He was admitted at 7 days of life with focal seizures and hypocalcaemia, hypomagnesaemia, hyperphosphataemia, and inappropriately low parathyroid hormone (PTH) levels. He was treated with i.v. calcium and magnesium infusions and discharged on oral calcium, magnesium, and alfacalcidol. He was re-admitted at 5 weeks with recurrent focal seizures and hypocalcaemia. Parents noticed he had stopped fixing and following over the previous week. Eye examination revealed nystagmus and absent red reflexes. He was urgently reviewed by ophthalmology who confirmed presence of dense bilateral cataract.

An activating variant in the calcium-sensing receptor (CASR) gene was confirmed. He was commenced on a s.c. PTH infusion and weaned off intravenous calcium infusion. Alfacalcidol was stopped and colecalciferol was started. Thiazide diuretics were commenced to reduce renal calcium excretion. Seizures settled after resolution of hypocalcaemia. He was operated for cataract at nine weeks of life.

The CASR is a G-protein coupled receptor which senses extracellular levels of calcium ion. Activating CASR gene variants result in an increased calcium sensitivity in parathyroid and renal cells, which in turn reduces the parathyroid set point and reduces renal calcium reabsorption. The clinical presentation varies from mild paraesthesia to nephrocalcinosis, basal ganglia calcifications and seizures. Cataracts are a recognised complication of hypoparathyroidism. However, as far as we are aware, this is the first reported case of cataract in an infant with activating CASR mutation. We therefore suggest that evaluation for cataract is required in this subgroup of patients.