THE SIGNIFICANCE OF THE ALANIN-GLYOXALATE -AMINOTRANSFERASE RESIDUAL ENZYME-ACTIVITY IN TREATMENT OF PRIMARY HYPEROXALURIA - REVIEW OF A FEW CASES

Primary Hyperoxaluria (PH 1) is an autosomal recessive inborn error of metabolism due to deficiency of peroxisomal enzym alanin: glyoxylate aminotransferase (AGT) in the liver. The increased oxalate excretion c auses calcium urinary stones, nephrocalcinosis. Most patients die in t erminal renal failure and systemic oxalosis in early life. The phenoty pic variability of PH 1 is caused by a marked heterogenity of the enzy me defect with different levels of residual AGT-activity. For therapeu tic measures in the individual cases the knowledge of their degree of residual enzym activity is mandatory. In the neonatal form with early nephrocalcinosis and severe renal insufficiency in infants no AGT acti vity can be detected in liver tissue. In adolescents with slow progres sion of nephrocalcinosis a residual enzyme activity of 10 - 20% of the mean control values exists. In PH 1, early diagnosis and a differenti ated therapeutic management is crucial for overall diagnosis. The mana gement varies from isolated liver transplantation before development o f renal/extrarenal organcomplications or combined liver-kidney transpl antation in case of renal insuffizient PH 1 patient with lack or extre mely reduced enzyme activity to conservative treatment with oral admin istration of pyridoxine, alkali citrate and high fluid intake in patie nts with acceptable AGT activity. In conservative management patients compliance is very important. Prenatal diagnosis is feasable by measur ing AGT-enzyme activity in fetal liver tissue.