UCD.- Argininosuccinic aciduria Neonatal form. Argininosuccinase deficiency
Incidence
Autosomal recessive. Second most common UCD. Inherited as an autosomal recessive trait, argininosuccinic aciduria affects both sexes equally.
Clinical Characteristics
Arginosuccinicaciduria is an autosomal recessive inherited deficiency of arginosuccinate lyase, an enzyme involved in the urea cycle. This leads to hyperammonemia and arginine deficiency. Onset occurs either soon after birth, with severe hyperammonemic coma that often proves to be fatal, or during childhood (see childhood or late onset). Neonates look normal during the first 24 hours. Then symptoms develop related to hyperammonemia. Clinically the common denominator, hyperammonemia, can manifest clinically by some or all of the following: Anorexia, irritability, heavy or rapid breathing, lethargy, vomiting, disorientation, somnolence, asterixis (rare), combativeness, obtundation, coma, cerebral edema and eventually death (if treatment is not forthcoming or effective).
Precipitants
Protein intake.
Provocation Tests
Protein intake produce elevated ammonia, not recommended.
Diagnostic Procedures
EB-F, EB-L. Diagnosis is made by clinical suspicion. It is essential to obtaining a blood ammonia level, which is elevated significantly in the symptomatic patient. This finding should lead to an immediate blood and urine amino acid quantitation, which confirms presence of argininosuccinic acid in both fluids. In addition, increased blood citrulline, glutamine, alanine, and lysine may be observed. Argininosuccinic acid lyase may be assayed in cultured fibroblasts, providing the definitive biochemical diagnosis. Urine orotic acid is elevated.