Antenatal and Neonatal Management of Siblings With Carbonic Anhydrase <scp>VA</scp> Deficiency

Carbonic anhydrase VA (CAVA) deficiency (OMIM 114761) is an ultra-rare inborn error of metabolism with fewer than 20 cases described. Affected infants present in the first days of life with hyperammonaemia, lactic acidosis, ketonaemia and encephalopathy. Prenatal genetic testing can facilitate the diagnosis of subsequent affected pregnancies and permit proactive clinical management to prevent metabolic decompensation. Here we describe the clinical course of two sibling infants antenatally diagnosed with CAVA deficiency who were monitored and managed in the newborn period without decompensation. The proband, their older brother, had presented on day four of life with marked lactic acidosis, hyperammonaemia and encephalopathy requiring haemofiltration due to CAVA deficiency. His brothers were each born in a tertiary neonatal setting. They were managed with regular 3-4 hourly breastfeeds with supplementary expressed breast milk and formula top-ups to ensure optimal nutrition. In addition, they received carglumic acid (100 mg/kg daily) for 5 days. Regular biochemical monitoring was undertaken with measurement of acid-base status and ammonia levels. In contrast to their older brother, these male siblings had unremarkable neonatal periods with no significant clinical or biochemical concerns, demonstrating that in a neonate known to be affected with CAVA deficiency, early intervention can be instituted to minimise the risk of metabolic decompensation in the neonatal period.