Arginase deficiency is a rare, autosomal recessive, disorder of the
urea cycle characterized by mild hyperammonaemia, hyperargininaemia, dibasic aminoaciduria and orotic aciduria, associated with progressive
spastic tetraplegia,
seizures, psychomotor retardation, and growth failure. We report a family who presented with their daughter at 4 years 11 months of age with an acute
encephalopathy. Initial laboratory results revealed hyperammonaemia (160 micromol/L; normal 0-34), hyperargininaemia (512 micromol/L; normal 23-86) and orotic aciduria. A diagnosis of
arginase deficiency was confirmed by
enzyme assay, and treatment with a modified
protein-restricted diet along with
sodium benzoate therapy was initiated. Over time, intellectual development has been normal, but the child developed spasticity in her lower extremities. Subsequently, the mother presented at 6 weeks of pregnancy seeking prenatal diagnosis. Prenatal testing for
arginase deficiency has only been reported in one other case.
Arginase is not expressed in cultured amniotic fluid cells or chorionic villus samples. Testing for
arginase activity assay in red blood cells, isolated by cordocentesis, was performed and predicted an unaffected fetus. The result was confirmed by postnatal
enzyme analysis of red cells from the newborn. On the basis of our experience, prenatal diagnosis of
arginase deficiency by cord red blood cell
arginase activity assay appears possible.