Hyperornithinaemia-hyperammonaemia-homocitrullinuria syndrome: a treatable genetic liver disease warranting urgent diagnosis

Hyperornithinaemia-hyperammonaemia-homocitrullinuria syndrome is an autosomal recessive disorder caused by a defect in ornithine translocase. This condition leads to variable clinical presentations, including episodic hyperammonaemia, hepatic derangement, and chronic neurological manifestations. Fewer than 100 affected patients have been reported worldwide. Here we report the first two cases in Hong Kong Chinese, who were compound heterozygous siblings for c.535C>T (p.Arg179*) and c.815C>T (p.Thr272Ile) in the SLC25A15 gene. When the mother refused prenatal diagnosis for the second pregnancy, urgent genetic testing provided the definitive diagnosis within 24 hours to enable specific treatment. Optimal management of these two patients relied on the concerted efforts of a multidisciplinary team and illustrates the importance of an expanded newborn screening service for early detection and treatment of inherited metabolic diseases.