Hyperammonemia in a Woman with Late-onset Ornithine Transcarbamylase Deficiency

Abstract

A 52-year-old woman developed vomiting and disturbance of consciousness after consuming raw fish and sushi on a trip. A blood test showed hyperammonemia (310 μg/dL) with a normal liver function. She fell into a deep coma, and her serum ammonia level increased to 684 μg/dL. L-arginine was administered as a diagnostic treatment for urea cycle disorder (UCD) and serum ammonia, and her consciousness levels improved. She was diagnosed with ornithine transcarbamylase deficiency (OTCD) by analyses of plasma amino acids, urinary orotic acid, and the OTC gene mutation. UCD should be considered for patients with hyperammonemia without severe liver function abnormalities.

Keywords: L-arginine; c.119G>A mutation; hyperammonemia; ornithine transcarbamylase deficiency; urea cycle; urea cycle disorder.

Figure 1.

Pedigree of the four-generation family in the present case. An oblique line indicates death. The age and cause of death are indicated below. Two of her cousins died from acute liver failure at the age of 16, and her daughter had a stillborn baby at 21 weeks of pregnancy due to amniotic infection.

Figure 2.

Abdominal contrast enhanced CT on admission. Both the liver and spleen were normal in size and shape. There were no findings indicating portal hypertension or portosystemic shunt.

Figure 3.

The clinical course of the present case and results of a genomic analysis of the OTC gene. (a) The serum ammonia level worsened rapidly from hospital day 1 to day 2 and improved rapidly after the administration of L-arginine on day 2. Her consciousness recovered on hospital day 5. (b) A genomic analysis revealed an Arg40His (c.119G>A) heterozygous mutation in the OTC gene.