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Background. The epidemiology of human herpesvirus 6 (HHV-6) encephalitis after allogeneic hematopoietic cell transplantation (HCT) and its relationship with HHV-6 reactivation have not been sufficiently characterized. Methods. This prospective, multicenter study of 230 allogeneic HCT recipients investigated the epidemiology of HHV-6 reactivation and HHV-6 encephalitis. Plasma HHV-6 DNA load was prospectively evaluated twice weekly until 70 days after HCT. Results. Cumulative incidence of positive HHV-6 DNA and high-level HHV-6 reactivation (plasma HHV-6 DNA ≥10 4 copies/mL) at day 70 after HCT was 72.2% and 37.0%, respectively. Multivariate analysis identified myeloablative conditioning (hazard ratio [HR], 1.9; P = .004), umbilical cord blood transplantation (UCBT) (HR, 2.0; P = .003), and male sex (HR, 1.6; P = .04) as risk factors for displaying high-level HHV-6 reactivation. HHV-6 encephalitis occurred in 7 patients, and cumulative incidence at day 70 was 3.0%. None of the144 patients without high-level HHV-6 reactivation and 7 of 86 patients (8.1%) with high-level HHV-6 reactivation developed HHV-6 encephalitis (P = .0009). Prevalence of HHV-6 encephalitis was significantly higher among patients receiving UCBT than in patients with other sources (cumulative incidence at day 70, 7.9% vs 1.2%, P = .008). In each of 7 patients with HHV-6 encephalitis, central nervous system (CNS) symptoms developed concomitant with peak plasma HHV-6 DNA (range, 21 656–433 639 copies/mL). Conclusions. High levels of plasma HHV-6 DNA are associated with higher risk of HHV-6 encephalitis. UCBT is a significant risk factor for HHV-6 encephalitis. HHV-6 encephalitis should be considered if CNS dysfunction develops concomitant to high-level plasma HHV-6 DNA after allogeneic HCT.

Graft failure (GF) is a life-threatening complication after allogeneic stem cell transplantation (SCT). Although salvage SCTs can be performed with haploidentical donor (HID) or cord blood (CB), no study has compared the performances of these two sources. Using nationwide registration data, we compared the transplant outcomes of patients who developed GF and underwent salvage transplantation from HID (n = 129) and CB (n = 570) from 2007 to 2016. The HID group demonstrated better neutrophil recovery (79.7 vs. 52.5% at 30 days, P < 0.001). With a median follow-up of 3 years, both groups demonstrated similar overall survival (OS) and nonrelapse mortality (NRM; 1-year OS, 33.1 vs. 34.6% and 1-year NRM, 45.1 vs. 49.8% for the HID and CB groups). After adjustments for other covariates, OS did not differ in both groups. However, HID was associated with a lower NRM (hazard ratio, 0.71; P = 0.038) than CB. The incidence of acute graft-versus-host disease (GVHD)-related deaths was significantly higher in the HID group, although infection-related deaths were observed more frequently in the CB group. HID may be a promising salvage SCT option after GF due to its faster engraftment and low NRM.

This prospective multicenter study aimed to determine the effects of human herpesvirus-6B (HHV-6B) reactivation on central nervous system (CNS) function in cord blood transplant (CBT) recipients. Our focus was to track HHV-6B reactivation and evaluate its association with delirium and cognitive function, specifically in the domains of verbal memory, attention/processing speed, and quality of life (QOL). A cohort of 38 patients participated in this study. Of the 37 patients evaluated, seven (18.9%) developed delirium, with six of these cases emerging after HHV-6B reactivation (median lag, 7 days). Evaluation of verbal memory showed that the final trial score for unrelated words at 70 days after transplantation was significantly lower than that before preconditioning ( P  = 0.004) among patients ( n  = 15) who experienced higher-level HHV-6B reactivation (median or higher maximum plasma HHV-6 DNA load for participating patients). Patients without higher-level reactivation did not show significant declines in verbal memory scores. QOL was assessed using the 36-item Short-Form Health Survey, and the social functioning score 1 year post-transplantation was significantly lower in patients who experienced higher-level HHV-6B reactivation than in those who did not. Our findings suggest that higher-level HHV-6B reactivation can detrimentally affect certain cognitive functions in CBT recipients.

Background CD36-deficient individuals may produce anti-CD36 antibodies through antigenic exposure to CD36, in situations including blood transfusions. Therefore, allogeneic hematopoietic stem cell transplantation (HSCT) from CD36-positive donors to CD36-negative patients remains a challenge. Case report A 64-year-old man with acute myeloid leukemia became refractory to platelet transfusions during chemotherapy. Anti-CD36 antibodies without anti-HLA antibodies were detected in serum, and the absence of CD36 expression on platelets and monocytes confirmed type I CD36 deficiency. The patient achieved complete remission, and received maintenance therapy with CD36-negative platelet transfusions. However, he relapsed soon afterward, and thus underwent peripheral blood stem cell transplantation (PBSCT) from a CD36-positive unrelated donor. The anti-CD36 antibody titer had decreased before the transplant, and the PBSCT-course was uneventful. The patient has been well without any complications associated with CD36 status mismatch. Discussion The few reports of allogeneic HSCT in patients with CD36 deficiency have suggested that anti-CD36 antibodies could be involved in several post-transplant complications, such as delayed platelet recovery, transfusion refractoriness, and transfusion-related acute lung injury. Our present case confirmed that stem cell transplantation from CD36-positive donors to negative patients is feasible, when it includes careful prior assessment of anti-CD36 antibody titers and interventions to attenuate them.

Reports of myelitis associated with human herpesvirus-6 (HHV-6) following allogeneic transplantation are rare. Of 121 cases of cord blood transplantation (CBT) performed at Nagano Red Cross Hospital, five cases (4.1%) of HHV-6 myelitis developed at around the time of engraftment. The major symptom identified in all five patients was superficial pain or pruritus linked to segmental levels of the spinal cord. Other identified symptoms were fever or low-grade fever in all five patients, autonomic nerve disorder in four patients, bladder and rectal disturbance in two patients, and extrapyramidal disorder in two patients. These symptoms were experienced primarily 16–39 days after CBT. HHV-6 PCR tests were all positive for cerebrospinal fluid and for plasma. Of the four cases tested by magnetic resonance imaging (MRI), three showed spinal cord abnormality. Antiviral therapy using foscarnet or ganciclovir was effective in every case. Although one case treated from 12 days after onset experienced long-term pain resembling postherpetic neuralgia, symptoms in the four cases were completely relieved after antiviral therapy. In summary, the major symptoms of HHV-6 myelitis were superficial pain linked to segmental levels of the spinal cord. Prognosis may be improved by early initiation of antiviral therapy.

Toxoplasmosis is a rare and possibly underestimated complication following hematopoietic stem cell transplantation (HSCT) associated with a high mortality rate, although the incidence of toxoplasmosis after HSCT in Japan has not been established. We retrospectively studied patients with toxoplasmosis after HSCT, and identified five patients who had been diagnosed with an acute exacerbation of toxoplasmosis among 279 HSCT recipients at our institution between 1998 and 2011, representing an incidence of 1.8 %. Among 87 autologous HSCT recipients, one definite case was diagnosed. The serological test for Toxoplasma gondii before HSCT was positive in 18 of 192 allogeneic HSCT recipients. Of the 18 seropositive patients, three had definite infections, and one had possible infection. All four definite cases were diagnosed at autopsy. In the definite cases, three allogeneic HSCT recipients had disseminated or pulmonary toxoplasmosis and one autologous HSCT recipient had toxoplasmic encephalitis, although toxoplasmosis was not suspected at the premortem examination due to non-specific clinical and radiological manifestations. Thus, acute exacerbation of toxoplasmosis should be suspected in recipients after HSCT. Early diagnosis and treatment for toxoplasmosis would certainly contribute to a decrease in mortality after HSCT.

The prognosis of pulmonary toxoplasmosis, including disseminated toxoplasmosis involving the lungs, following hematopoietic stem cell transplantation (HSCT) is extremely poor due to the difficulties associated with early diagnosis and the rapidly progressive deterioration of multiorgan function. In our institution, we identified nine cases of toxoplasmosis, representing incidences of 2.2 and 19.6 % among all HSCT recipients and seropositive HSCT recipients, respectively. Of the patients with toxoplasmosis, six had pulmonary toxoplasmosis. Chest computed tomography (CT) findings revealed centrilobular, patchy ground-glass opacities ( n  = 3), diffuse ground-glass opacities ( n  = 2), ground-glass opacities with septal thickening ( n  = 1), and marked pleural effusion ( n  = 1). All cases died, except for one with suspected pulmonary toxoplasmosis who was diagnosed by a polymerase chain reaction assay 2 days after the onset of symptoms. In pulmonary toxoplasmosis, CT findings are non-specific and may mimic pulmonary congestion, atypical pneumonia, viral pneumonitis, and bronchopneumonia. Early diagnosis and treatment is crucial for overcoming this serious infectious complication. Pulmonary toxoplasmosis should be considered during differential diagnosis in a recipient with otherwise unexplained signs of infection and CT findings with ground-glass opacities, regardless of the distribution.

Mixed‐phenotype acute leukemia (MPAL) with FLT3‐TKD mutations is a rare and challenging subtype of leukemia. Effective management strategies are crucial for improving patient outcomes. A 31‐year‐old man with FLT3‐TKD‐mutated MPAL achieved hematological remission through the JALSG ALL202‐O protocol and gilteritinib, followed by cord blood transplantation (CBT). Post‐transplant complications included adenovirus‐induced hemorrhagic cystitis, managed with bladder irrigation and ribavirin, and engraftment failure, necessitating a second CBT on Day 35. Subsequent adenoviral conjunctivitis resolved with vidarabine. The patient achieved neutrophil engraftment by Day 76 and was discharged on Day 173 without relapse. This case highlights the importance of vigilant supportive care and tailored therapy in managing MPAL with FLT3 mutations, especially in the context of post‐transplant complications.

TP53 gene abnormality has been reported to be an unfavorable prognostic factor in acute myeloid leukemia (AML). However, almost all studies of TP53 gene abnormality so far have been limited to mutation searches in the DNA binding domain. As there have been few reports examining both mutation and deletion over the full-length of the TP53 gene, the clinical characteristics of TP53 gene abnormality have not yet been clearly established. In this study, TP53 gene mutation was observed in 7.3% of the total 412 de novo AML cases (33 mutations in 30 cases), with mutation outside the DNA binding domain in eight cases (27%). TP53 gene deletion was observed in 3.1% of 358 cases. All cases had monoallelic deletion with TP53 gene mutation on the opposite allele. Multivariate analysis demonstrated that TP53 gene mutation in the DNA binding domain and outside the DNA binding domain was an independent poor prognostic factor for overall survival and relapse-free survival among the total cohort and it is also an unfavorable prognostic factor in FLT3-ITD-negative AML cases aged 70 years or below with intermediate cytogenetic prognosis. In stratified treatment, full-length search for TP53 gene mutation is therefore very important.

Graft failure (GF) remains a major problem in cord blood transplantation (CBT). In 36 adult patients undergoing CBT at our hospital between July 2003 and December 2009, six patients developed GF (primary, n  = 5; secondary, n  = 1). All six patients underwent second stem cell transplantation (SCT). Three patients had acute myeloid leukemia, one had acute lymphoblastic leukemia, one had chronic myeloid leukemia, and one had aplastic anemia. Five patients were complicated with sepsis before the second SCT. The median elapsed time from first CBT to the diagnosis of primary GF was 27 days. Secondary GF was diagnosed on day 567. The median elapsed time from primary GF to second SCT was 9 days. In the patient with secondary GF, the elapsed time was 35 days. Cord blood grafts were used in 5 patients and a matched sibling donor in one patient. All 6 patients underwent second transplantation following a modified ‘1-day’-based preparative regimen consisting of fludarabine (30 mg/m 2 , 1 day, n  = 2; 2 days, n  = 1; 3 days, n  = 3), cyclophosphamide (2 g/m 2 ), and total body irradiation (2 Gy). All patients achieved neutrophil engraftment, and the median elapsed time from second SCT to engraftment was 35 days. Four patients remain alive between 5 and 38 months after second SCT. ‘1-day’-based short-term conditioning may be a promising salvage regimen.