Abstract
Cystinuria is an autosomal recessive disorder in which the renal reabsorption of cystine, arginine, lysine and ornithine are disturbed. The two genes, the pathogenic forms of which are responsible for the disorder, are SLC7A9 and SLC3A1. In this study, we describe a disease that has a new c.916A> T variant (p. K306 *) in exon 5 of the SLC3A1 gene. This variant results in the NMD phenomenon in which the protein product is not produced because of mRNA destruction. In 2020, blood sample of a 41-yr-old man from east Azerbaijan, Iran together with his parents were collected to be studied. PCR and direct sequencing were performed to detect the possible SLC3A1 variant. Whole-gene sequence analysis done by Mutation surveyor Software revealed a novel nonsense homozygous variant in exon 5 of the gene. Parental Sequence Analysis shows that they are heterozygous. According to ACMG guideline, this variant is considered as pathogen. Finding serious mutations can allow rapid screening for cystinuria by analyzing common mutations. It should also be considered as a pathogenic variant in patients' cystinuria.