[Biochemical and molecular diagnosis of primary hyperoxaluria type 1: Tunisian study about 15 cases]

The primary type 1 hyperoxaluria (HP1) is the most frequent and severe form of the primary hyperoxaluriae. It is related to an enzymatic deficit in alanine glyoxylate aminotransferase (AGT). It is a recessive autosomic disease. Rare in Europe, it is responsible for 13% of the end stage renal failure in the Tunisian child.

The aim of this work is to evaluate the biological and molecular examinations contributing with the early diagnosis and the follow-up of the HP1 patients and to test their response to pyridoxin.

A prospective study of 15 children who have oxaluria lower than 500 μmol/l and normal renal function is carried out. The cristalluria study, oxaluria and the glycolate-glycerate urinary ratio were carried out on all the patients. The so-called mutation maghrebean T853 (Ile244 Thr) was detected by direct sequencing of the exon 7 gene AGXT. The response to pyridoxin was tested among 13 patients.

The oxaluria concentration was greater or equal to 1000 μmol/l in nine cases (60%) and ranging between 600 and 1000 μmol/l in the remaining cases. The oxaluria flow was significantly high depending on the age. The glycolaturia was high among eight patients (57%). In 61,5% of the cases, the most frequent crystalline species was whewellite (C1). The "maghrebin" mutation was identified in nine patients at the heterozygous state, showing 25% allelic frequency. The response to pyridoxin was observed in the 13 tested cases.

The HP1 is frequent in our country from where the need for an early diagnosis. The use of simple biochemical tools such as the study of the cristalluria, the morphological analysis of stones and the oxaluria allow to direct the diagnosis towards a HP1, confirmed by the glycolaturia determination. The molecular biology is required in the atypical forms.