{Reference Type}: Case Reports {Title}: Outcome of Cyclophosphamide Treatment Following Hematopoietic Stem Cell Transplantation in a Thalassemia Patient: A Case Study. {Author}: M Bahlol H;M Khalil S;R El-Shanshory M;L Salem M; {Journal}: Iran J Immunol {Volume}: 21 {Issue}: 2 {Year}: 2024 06 30 {Factor}: 1.206 {DOI}: 10.22034/iji.2024.101584.2752 {Abstract}: Hematopoietic stem cell transplantation (HSCT) is the only curative therapy for β-thalassemia major in children. However, it often induces graft-versus-host-disease (GVHD), which is associated with complications. In the present study, we used cyclophosphamide (Cy) to treat a thalassemia patient post-HSCT to reduce the adverse effects of GVHD. We monitored the numbers and phenotype of granulocytes. In this case study, an 11-year-old female patient, diagnosed with β-thalassemia major (Pesaro class II), was treated with Cy before and after HSCT with mobilized CD34+ cells. Both the relative and absolute granulocyte counts, as well as CD33+CD11b+ cell counts, increased significantly after HSCT until day 56. However, they suddenly began to decrease after day 56, accompanied by severe diarrhea, skin rash, and a decrease in bilirubin levels compared to day -12. Furthermore, compared to day -12, IL-22 levels increased until day 56, and then decreased, while IDO levels continued to rise after day 56. Our data suggest the potential use of IL-22 and IDO as biomarkers for GVHD assessment. It also indicates that Cy promotes HSCT reconstitution by increasing CD33+CD11b+ cells, which may play a crucial role in reducing GVHD risks. However, further studies are needed to elucidate the mechanism behind GVHD recurrence.