Expanding the Genetic Spectrum of AGXT Gene Variants in Egyptian Patients with Primary Hyperoxaluria Type I

Abstract

Introduction:

Approximately 80% of primary hyperoxaluria cases are caused by primary hyperoxaluria type 1 (PH1, OMIM# 259900), which is characterized by pathogenic variants in the AGXT gene, resulting in deficiency of the liver-specific enzyme alanine-glyoxylate aminotransferase (AGT). This leads to increased production of oxalate, which cannot be effectively eliminated from the body, resulting in its accumulation primarily in the kidneys and other organs.

Subjects and Methods:

This study included 17 PH1 Egyptian patients from 12 unrelated families, recruited from the Inherited Kidney Disease Outpatient Clinic and the Dialysis Units, Cairo University Hospitals, during the period from January 2018 to December 2019, aiming to identify the pathogenic variants in the AGXT gene.

Results:

Six different variants were detected. These included three frameshift and three missense variants, all found in homozygosity within the respective families. The most common variant was c.121G>A;p.(Gly41Arg) detected in four families, followed by c.725dup;p.(Asp243GlyfsTer12) in three families, c.33dup;p.(Lys12Glnfs156) in two families, and c.731T >C;p.(Ile244Thr), c.33delC;p.(Lys12Argfs34), and c.568G>A;p.(Gly190Arg) detected in one family each.

Conclusion:

Consanguineous Egyptian families with history of renal stones or renal disease suspicious of primary hyperoxaluria should undergo AGXT genetic sequencing, specifically targeting exons 1 and 7, as variants in these two exons account for >75% of disease-causing variants in Egyptian patients with confirmed PH1.