1471 delTTCT a Common Mutation of Tunisian Patients with Lysinuric Protein Intolerance

Background: Lysinuric protein intolerance is an inherited aminoaciduria caused by defective cationic amino acid transport. It is an autosomal recessive disease caused by mutations in the SLC7A7 gene. The objective of this study was to identify the mutations of Tunisians patients in order to offer the genetic counseling and the prenatal diagnosis to families. Methods: Five affected Tunisian children (4 girls and 1 boy) belonging to four consanguineous families were considered. The diagnosis was made based on the plasma for amino acids quantification by Ion Exchange chromatography, the DNA for mutational analysis by DHPLC and sequencing, and the amniotic fluid for prenatal diagnosis. Results: For the 5 patients, clinical features were dominated by failure to thrive, bone marrow abnormalities, hepatosplenomegaly, and mental retardation. The diagnosis for all patients was confirmed by biochemical analysis with hyperammonemia, hyperexcretion of urinary dibasic amino acids, and a high amount of orotic acid in the urine. The 1471 delTTCT mutation was identified in exon 9 in the homozygous state for all Tunisian patients. Genetic counseling was performed for three out of four families, four heterozygous and two homozygous healthy siblings were identified. The result of prenatal diagnosis showed the presence of the 1471 deITTCT mutation in the homozygous state for the third pregnancy and heterozygous state for the fourth. Conclusions: The 1471 delTTCT mutation seems to be a common mutation of Tunisian population. The identification of this specific mutation provides a tool for confirmatory diagnosis, genetic counseling, and prenatal diagnosis.