INBORN-ERRORS OF UREA SYNTHESIS

Inborn errors of urea synthesis can present in the newborn period as a catastrophic illness or later in childhood or adulthood with an indol ent course punctuated by hyperammonemic episodes. Because symptoms mim ic other neuropsychiatric disorders, it is common for there to be a de lay in diagnosis, often with dire consequences. Diagnosis relies on th e combination of clinical suspicion and the measurement of ammonium, l actate, and amino acids in plasma and organic acids and erotic acid in urine. Treatment involves nitrogen restriction combined with the stim ulation of alternate pathways of waste nitrogen excretion. More recent ly liver transplantation has been performed as enzyme replacement ther apy. The outcome is poor in children who survive prolonged neonatal hy perammonemic coma, with most manifesting developmental disabilities. T he etiology of neuronal. injury in this disorder is unclear but may in volve some combination of ammonia/amino acid accumulation, neurotransm itter alterations, and excitotoxic injury. Gene therapy holds the prom ise of improved treatment in the future.