Molecular abnormalities in Type I primary hyperoxaluria.

Type I is the most common form of primary hyperoxaluria, also called oxalosis when systemic involvement has occured. This recessive autosomal inherited inborn error of metabolism is characterized by a defect of alanine: glyoxylate aminotransferase (AGT), which is a specific liver enzyme. This protein is responsible for glyoxylate detoxification only when it is located in the peroxisome. The clinical and bio-chemical phenotypes are neither correlated with the residual catalytic activity of AGT nor with its immunoreactivity. Most patients display less than 2% catalytic activity or no immunoreactive protein; peroxisome-to-mitochondrion mistargeting is the main feature of the disease at the subcellular level. The cDNA and genomic DNA have been cloned and sequenced and the gene has been located on the long arm of chromosome 2 in the q36-37 region. To date, four polymorphisms, seven point mutations and one complete deletion have been reported; 30% of the patients have unidentified gene abnormalities.