A Comprehensive Study of Disease-Causing Variants in <i>PAH</i>, <i>QDPR</i>, <i>PTS</i>, and <i>PCD</i> Genes in Iranian Patients with Hyperphenylalaninemia: A Systematic Review

Abstract

<b><i>Background:</i></b> Hyperphenylalaninemia (HPA) is an autosomal recessive disorder that results from a deficiency in the phenylalanine hydroxylase enzyme (PAH) or from a flaw in the genes that are responsible for the biosynthesis or regeneration of the cofactor tetrahydrobiopterin (BH4), including <i>GCH1</i>, <i>SR</i>, <i>QDPR</i>, <i>PTS</i>, and <i>PCD</i>. Identification of disease-causing variants in these genes can help physicians and clinical geneticists in differential diagnosis, appropriate prescription drugs, and saving time and cost. This study attempted to identify these genes’ most prevalent disease-causing variants in Iranian HPA patients. <b><i>Summary:</i></b> This study was performed under the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Before it started, the flow work and inclusion/exclusion criteria were published as a protocol in PROSPERO (CRD42021273705). We conducted a comprehensive search on December 10, 2022, on international online databases, including Web of Science, Scopus, EMBASE, Science Direct, PubMed/Medline, Google Scholar, SID, ISC, and Magiran search engine, to find pertinent publications. Some studies were chosen based on inclusion and exclusion criteria. Altogether, 1,243 Iranian patients from 13 articles were considered. In total, we identified 129 distinct disease-causing variants in <i>PAH</i> (20 novel variants), 29 in <i>QDPR</i> (17 novel variants), 15 in <i>PTS</i> (seven novel variants), and one novel variant in <i>PCD</i>. Twenty disease-causing variants for <i>PAH</i>, 18 for <i>QDPR</i>, and 8 for <i>PTS</i> are included in the genes’ proposed genetic diagnostic panels. These panels include more than 75% of the documented disease-causing variants in the Iranian population. <b><i>Key Messages:</i></b> The findings of this research illustrated the spectrum of disease-causing variants in the <i>PAH</i>, <i>QDPR</i>, <i>PTS</i>, and <i>PCD</i> genes identified in Iranian HPA patients. Common disease-causing variants of these genes may be chosen as a preliminary diagnostic panel for early diagnosis and lowering therapy costs.