Neonatal citrullinemia: novel, reversible neuroimaging findings correlated with ammonia level changes

Citrullinemia type I is an autosomal recessive disorder of the urea cycle in which a patient lacks the cytosolic enzyme, argininosuccinic acid synthetase. This enzyme deficiency results in elevated levels of ammonia, glutamine, and citrulline. The accumulation of ammonia and glutamine causes neurodegenerative changes that are detectible on magnetic resonance imaging. This is the first case report of citrullinemia with repeat magnetic resonance images and electroencephalographs in the acute phase of hyperammonemia.

This 3800 g white boy was born at 40 weeks 4 days gestation to a 25-year-old mother. He was delivered at home to a certified midwife with no reported complications. He was doing well until day of life 4, when the mother reported he would no longer latch to feed. He was observed to have markedly elevated ammonia levels and ultimately diagnosed with citrullinemia type I. The initial magnetic resonance image was markedly abnormal. After aggressive medical management, his repeat magnetic resonance image revealed marked improvement in the acute setting.

Early and aggressive management of hyperammonemia can result in improved magnetic resonance imaging findings in the acute setting. It is too early to know if this will translate to an improved clinical outcome. Clinical suspicion must remain high for urea cycle disorders in neonates with magnetic resonance image changes similar to those resulting from hypoxic-ischemic injury.