Somatic Mutations in Brazilian Patients with Paroxysmal Nocturnal Hemoglobinuria: A Comprehensive Analysis

Patricia Eiko Yamakawa ^1* Caio Perez Gomes ² Agatha Ribeiro Mendes ² Florencio Porto Freitas ³ Fabiana Bettoni ⁴ Vinícius Campos de Molla ¹ Matheus Vescovi Gonçalves ¹ Jéssica Branquinho ² Beatriz Ribeiro Nogueira ² Joao Bosco Pesquero ² Celso Arrais-Rodrigues ¹

• ¹ Department of Hematology, Universidade Federal de São Paulo, São Paulo, Rio Grande do Sul, Brazil
• ² Department of Biophysics, Universidade Federal de São Paulo, São Paulo, Rio Grande do Sul, Brazil
• ³ Rudolf Virchow Center for Integrative and Translation Bioimaging, Julius-Maximilians-Universität Würzburg (JMU), Wuerzburg, Germany
• ⁴ Molecular Oncology center, Hospital Sirio Libanes, São Paulo, Rio Grande do Sul, Brazil

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal hematopoietic stem cell disease characterized by acquired abnormalities in the phosphatidylinositol glycan class A (PIG-A) gene.This study analyzed PIG-A gene using polymerase chain reaction (PCR) followed by Sanger sequencing of 31 Brazilian patients with PNH, including 23 with classical PNH and 8 with subclinical PNH (aplastic anemia and a PNH clone).A diverse spectrum of acquired PIG-A variants was identified, encompassing insertions, deletions, and single-base substitutions. The majority of variants identified (17 out of 29) were deemed likely pathogenic for paroxysmal nocturnal hemoglobinuria (PNH). Six variants have undetermined significance (VUS) and six variants are probably benign. Somatic variants exhibited variability in type and location among the patients, with a predominance of small deletions and simple base changes. Notably, 41% of the variants were frameshift and 35% were missense. Among the 23 patients with hemolytic PNH, 19 had at least one detectable pathogenic variant. Subclinical PNH cases were characterized solely by polymorphisms.In conclusion, the somatic variants in Brazilian PNH patients displayed variability in both site distribution and type. Contrary to mutational hotspots observed in previous studies, none were identified in this cohort. No specific correlation between the clinical characteristics of hemolytic PNH patients and their variants was found, likely due to the extensive variety of mutations.* primer sequences derived from Ilda et al. 2 ** primer designed in-house.