Endothelial cell (EC) activation has been suspected of triggering a group of rare and dismal complications that can occur after allogeneic hematopoietic stem cell transplantation (HSCT). Capillary leak syndrome, engraftment syndrome, transplant-associated microangiopathy, diffuse alveolar hemorrhage, and idiopathic pneumonia syndrome are the main nosological entities. Post-HSCT endotheliitis can be triggered by chemotherapy, infections, and calcineurin inhibitors, but allogeneic reactivity is claimed to be the common denominator. Endothelial damages are thought to activate several deleterious pathways (proapoptotic, procoagulant, proinflammatory) and can lead to multiorgan failure; however, clinical manifestations of each syndrome overlap, and their relationship with graft-versus-host disease could be minimal. The lack of well-defined diagnostic criteria does not allow for a clear-cut comparison in the current literature. Therapeutic efforts have been made to intercept the pathogenic mechanisms leading to EC dysfunction, but remission rates and survival remain mostly unsatisfactory. In this article, we have reviewed the incidence, clinical features, and treatment approaches of EC activation syndromes, and we plead for the development of internationally accepted standard definitions.

Cytoplasmic vacuoles in precursors can be seen in a number of clinical settings, including copper deficiency, zinc toxicity, alcohol abuse, antibiotic treatment, myelodysplasia, and VEXAS syndrome. Gurnari et al asked how common VEXAS syndrome is in patients whose bone marrow aspirates show this distinctive feature, finding 2 diagnoses of VEXAS among 24 cases with vacuoles.

TET2 is frequently mutated in myeloid neoplasms. Genetic TET2 deficiency leads to skewed myeloid differentiation and clonal expansion, but minimal residual TET activity is critical for survival of neoplastic progenitor and stem cells. Consistent with mutual exclusivity of TET2 and neomorphic IDH1/2 mutations, here we report that IDH1/2 mutant–derived 2-hydroxyglutarate is synthetically lethal to TET dioxygenase–deficient cells. In addition, a TET-selective small-molecule inhibitor decreases cytosine hydroxymethylation and restricted clonal outgrowth of TET2 mutant but not normal hematopoietic precursor cells in vitro and in vivo. Although TET inhibitor phenocopied somatic TET2 mutations, its pharmacologic effects on normal stem cells are, unlike mutations, reversible. Treatment with TET inhibitor suppresses the clonal evolution of TET2-mutant cells in murine models and TET2-mutated human leukemia xenografts. These results suggest that TET inhibitors may constitute a new class of targeted agents in TET2-mutant neoplasia. Significance: Loss-of-function somatic TET2 mutations are among the most frequent lesions in myeloid neoplasms and associated disorders. Here we report a strategy for selective targeting of residual TET dioxygenase activity in TET-deficient clones that results in restriction of clonal evolution in vitro and in vivo. See related video: https://aacrjournals.org/webinar-minimal-tet-activity-targetable-vulnerability-tet2-and-neomorphic-idh12-mutant

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Aplastic anemia (AA) is a bone marrow failure syndrome characterized by pancytopenia and an empty bone marrow. Standard treatments for AA include immunosuppressive therapy and bone marrow transplantation (BMT). BMT is the preferred option for young AA patients with a sibling donor, whereas in older patients or in those to be grafted from an unrelated donor BMT is exploited as second-line treatment. Current results of BMT for AA demonstrate cure rates up to 80 and 70% in BMT from HLA-matched siblings and unrelated donor, respectively, with age and stem cell source largely affecting the outcome. BMT is also a potential treatment option for paroxysmal nocturnal hemoglobinuria, a rare hematological disorder characterized by complement-mediated intravascular hemolytic anemia, thrombophilia and bone marrow failure.

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Liver blood test anomalies are common after allogeneic hematopoietic stem cell transplantation (allo-HSCT), but their cause often remains difficult to identify. Our objective was to evaluate the safety and utility of liver biopsies in patients who underwent allo-HSCT. In a retrospective single-center cohort study, we reviewed all cases of patients who underwent liver biopsy between June 2005 and July 2017. During this period, 54 biopsies were performed in 45 patients, in which 38 patients underwent allo-HSCT for malignant and 7 for nonmalignant hematological disorders. Median time between allo-HSCT and liver biopsy was 213 days. Seven biopsies were percutaneous, and 47 were transjugular. No adverse event related to the biopsy procedure occurred; 94.5% biopsies (51 of 54) led to a histological diagnosis. Cholestatic graft-versus-host disease was histologically demonstrated in 16 biopsies (30%); hepatitis-like graft-versus-host disease in 9 biopsies (17%); nonalcoholic steatohepatitis in 6 biopsies (9%); regenerative nodular hyperplasia in 4 biopsies (5%); and drug-induced liver injury, sinusoidal obstruction syndrome, and viral hepatitis each in 3 biopsies (5%). Association between clinical, laboratory, imaging and pathological features was poor. Only 34% of physicians' prebiopsy hypotheses were confirmed by pathological findings. Patient management was influenced by liver biopsy results in 65% of cases, allowing us to identify a new diagnosis (n = 13), rule out a differential diagnosis (n = 14), or confirm the main hypothesis (n = 6). In conclusion, liver biopsy is a safe and useful technique to investigate liver blood test anomalies following allo-HSCT.

Idiopathic aplastic anemia (IAA) is a rare autoimmune bone marrow failure disorder initiated by a human leukocyte antigen (HLA)-restricted T cell response to unknown antigens. As for other autoimmune disorders, the predilection for certain HLA profiles seems to represent an etiologic factor, however, the structure-function patterns involved in the self-presentation in this disease remain unclear. Herein we analyzed the molecular landscape of HLA complexes of a cohort of 300 IAA patients and almost 3000 healthy and disease controls, by deeply dissecting their genotypic configurations, functional divergence, self-antigen binding capabilities and T cell receptor (TCR) repertoire specificities. Specifically, analysis of the evolutionary divergence of HLA genotypes (HED) showed that IAA patients carried class II HLA molecules whose antigen binding sites were characterized by a high level of structural homology, only partially explained by specific risk allele profiles. This pattern implies reduced HLA binding capabilities, confirmed by binding analysis of hematopoietic stem cell derived self-peptides. IAA phenotype was associated with the enrichment in a few amino acids at specific positions within the peptide binding groove of DRB1 molecules, affecting the interface HLA-antigen-TCR β and potentially constituting the basis of T-cell dysfunction and autoreactivity. When analyzing associations with clinical outcomes, low HED was associated with risk of malignant progression and worse survival, underlying reduced tumor surveillance in clearing potential neoantigens derived from mechanisms of clonal hematopoiesis. Our data shed light on the immunogenetic risk associated with IAA etiology and clonal evolution, and on general pathophysiological mechanisms potentially involved also in other autoimmune disorders.