Hyperammonemia in ornithine transcarbamylase‐deficient recipients following living donor liver transplantation from heterozygous carrier donors

Ornithine transcarbamylase deficiency (OTCD) is a urea cycle disorder of X‐linked inheritance, affecting the detoxification of excess nitrogen and leading to hyperammonemia (hyper‐NH₃). Living donor liver transplantation (LDLT) has been applied for the treatment of OTCD. This case series retrospectively reviewed two OTCD patients who experienced hyper‐NH₃ following LDLT. The first case was a 5‐year‐old girl who had onset of OTCD at 2 years of age. Ornithine transcarbamylase (OTC) enzyme activity was 62% for the donor and 15% for the recipient. The patient suffered from recurrence of hyper‐NH₃ within 2 months following LDLT. The second case was a 5‐year‐old girl who had onset of OTCD at 3 years of age. OTC enzyme activity was 42.6% for the donor and 9.7% for the recipient. The patient suffered hyper‐NH₃ for 12 days starting on the date of surgery. Both of the patients transiently required continuous veno‐venous hemodialysis; however, they are currently doing well without intensive medical treatment. The use of asymptomatic OTCD heterozygous donors in LDLT has been accepted with careful examination. However, an OTCD heterozygous carrier donor should be avoided if there is another donor candidate, due to the potentially fatal condition of hyper‐NH₃ following LDLT.