Maple syrup urine disease (MSUD) is an autosomal recessive disorder associated with impaired metabolism of branched-chain amino acids (BCAA) leucine, isoleucine, and valine. Children with MSUD suffer from bouts of metabolic decompensation, which may lead to neurological damage. Liver transplantation from unrelated deceased donors has been considered curative. The natural history of the disease following transplantation using a haploidentical (obligate heterozygous) living donor is still unclear, although previously described as favorable. We describe acute metabolic crises in a 20-month-old child with MSUD type II. The first well-documented one occurred 5 months after a successful liver transplantation from his mother. The patient developed encephalopathy with progressive lethargy and seizures after an episode of gastroenteritis with dehydration. Plasma levels of leucine, isoleucine, and valine were markedly elevated and alloisoleucine was detected. He promptly responded to dialysis and BCAA-free dietetic management and subsequently could resume a normal diet. Since then he has had another symptomatic metabolic crisis with seizures. This case strongly suggests that some recipients of liver transplantation from a haploidentical parent possess limited capacity to oxidize BCAA at the time of catabolic stress and dehydration and remain at risk of severe metabolic crises. Thus, careful metabolic monitoring and prompt treatment post liver transplantation are still required to avoid neurological sequelae of MSUD, particularly if the donor is heterozygous for MSUD.
Keywords: Heterozygous donor; Liver transplant; MSUD; Metabolic crisis.