Objectives: This study aimed to identify and analyse ATP7B variants in Iraqi adults with Wilson disease (WD) by long-read next-generation sequencing. Methods: This cross-sectional study was conducted at the Poisoning Consultation Center at Ghazy Al-Hariri Hospital for Surgical Specialties and the Gastroenterology Consultation Clinic at Baghdad Teaching Hospital, Medical City in Baghdad, Iraq. Unrelated patients with clinical and biochemical features suggestive of WD were recruited between October 2022 and October 2023. DNA was extracted from peripheral blood samples. Variants in the ATP7B gene were identified using long-read next-generation sequencing and then analysed by in-silico tools. Results: A total of 45 patients were recruited in which 59 unique variants were detected; of them, 47 were deleterious, 9 were variants of uncertain significance (VUS) and 3 had a conflicting interpretation of pathogenicity. Those variants were detected in 80 out of 90 alleles of the ATP7B gene. Of the participants, 23 (51.1%) patients had 2 deleterious variants (8 in homozygous and 15 in compound heterozygous state); 12 (26.7%) patients had 1 deleterious variant plus 1 VUS or 1 with conflicting pathogenicity; and 10 (22.2%) patients were carriers of a single disease-causing variant. The most frequent variant, c.4021G>A (p.Gly1341Ser), was detected in 5 alleles, while c.3191A>C (p.Glu1064Ala) was detected in 4 alleles, followed by c.2165dupT (p.Arg723GlufsTer32) and c.3247C>T (p.Leu1083Phe), each detected in 3 alleles. Among the 59 variants, 42 were missense, 9 were frameshift, 6 were stop-gain, 2 were splice-donors and 1 was an in-frame deletion. The variant H1069Q, which is common worldwide, was not detected in this study. Conclusions: The ATP7B mutational spectrum in Iraqi patients with WD is significantly diverse, despite high rates of consanguinity. Evidence was provided for 8 variants to be considered for reclassification as deleterious. The diagnostic criteria for those with high Leipzig scores with only a single deleterious variant remain questionable.
