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The intestinal microbiota is an important prognostic factor for allogeneic hematopoietic stem cell transplantation (allo-HCT), and decreased diversity of the intestinal microbiota is linked to shorter overall survival, high transplant-related mortality, and acute graft-versus-host disease (GVHD). Major factors that alter the intestinal microbiota during allo-HCT are broad-spectrum antibiotics and intestinal GVHD. Broad-spectrum antibiotics dysregulate the immune system and impair intestinal epithelial regeneration by reducing beneficial commensal bacteria and activating mucus-degrading bacteria, which disrupts the colonic barrier function. Intestinal GVHD leads to decreased secretion of antimicrobial peptides into the intestinal lumen, as well as mitochondrial dysfunction in the intestinal epithelium, altering the intestinal microbiota. Various therapeutic approaches targeting the intestinal microbiota have been investigated in clinical trials. Protecting the intestinal microbiota may further enhance the safety and efficacy of allo-HCT by regulating intestinal immune responses, promoting intestinal epithelial regeneration, and facilitating the production of beneficial metabolites derived from commensal bacteria.

A 25-year-old male with a medical history of stress polycythemia was admitted to a previous hospital for leukocytosis, anemia, and thrombocytopenia. Bone marrow examination revealed left-shifted myeloid hyperplasia without increased blasts and normal male karyotype. No mutations of JAK2, V617F, and colony-stimulating factor 3 receptor gene (CSF3R) were detected. Fluorescence in-situ hybridization for BCR-ABL1 and FIP1L1-PDGFRA were negative. Based on these findings, a diagnosis of an unclassifiable myeloproliferative neoplasm was made, and he was started on hydroxyurea treatment. He was referred to our hospital in April 2016 for transfusion dependence. Bone marrow examination performed at our hospital revealed granulocytic dysplasia and CSF3R T618I was detected. After induction therapy, CSF3R T618I became undetectable, and he went on to undergo allogeneic stem cell transplantation in October 2016. He has been in remission for >4 years posttransplantation. CSF3R T618I is one of the genes responsible for chronic neutrophilic leukemia and atypical chronic myeloid leukemia, suggesting its involvement in the pathogenesis of this case.

A 22-year-old woman presented with high fever, chest tightness and cough in January 20XX. Since CT scans revealed an anterior mediastinal mass, percutaneous needle biopsies of the mass were performed and she was diagnosed with T-cell lymphoblastic lymphoma (T-LBL). After the immunophenotype of lymphocytes in her pleural effusion had been identified, she received CHOP therapy because her dyspnea worsened, and induction therapy for acute lymphoblastic leukemia was subsequently performed after confirmation of her diagnosis as T-LBL. During this induction therapy, she developed paralytic ileus. One week thereafter, she suddenly exhibited visual disturbance, headache and nausea. Her cerebrospinal fluid was normal. Magnetic resonance imaging showed symmetrical high signal intensities on T2-weighted and fluid-attenuated inversion recovery images, and low signal intensities on T1-weighted images in the cortical and subcortical white matter of the posterior parietal and occipital lobes. Based on these findings, she was diagnosed as having posterior reversible encephalopathy syndrome (PRES). During chemotherapy for hematologic malignancies, some patients with PRES reportedly develop paralytic ileus or tumor lysis syndrome. PRES should be considered in patients with neurological abnormalities following such complications during chemotherapy.

A 76-year-old woman presented with vaginal bleeding and discharge in September 2009. She was admitted to our hospital because a tumor of 5 cm in diameter was found in the vagina in a nearby clinic. She was diagnosed with primary vaginal diffuse large B-cell lymphoma (DLBCL) on biopsy of the tumor because CT, MRI and FDG-PET showed no area of lymphomatous involvement other than the vagina and direct involvement into the bladder. She achieved complete response (CR) after chemotherapy followed by localized radiation therapy, but she had a relapse in the central nervous system (CNS) two months after CR. A study of 57 reported cases of primary vaginal lymphoma suggested that the most common histologic type was DLBCL, and most of patients were in a localized stage and responded well to combination of chemotherapy and radiation therapy. To date, two cases of primary vaginal lymphoma with a relapse in the CNS have been reported. We presumed that direct involvement into the bladder of vaginal lymphoma contributed to the relapse in the CNS in this case.