Oxidative DNA Damage, Inflammatory Signature, and Altered Erythrocytes Properties in Diamond-Blackfan Anemia.

Molecular pathophysiology of Diamond-Blackfan anemia (DBA) involves disrupted erythroid-lineage proliferation, differentiation and apoptosis; with the activation of p53 considered as a key component. Recently, oxidative stress was proposed to play an important role in DBA pathophysiology as well. CRISPR/Cas9-created Rpl5- and Rps19-deficient murine erythroleukemia (MEL) cells and DBA patients' samples were used to evaluate proinflammatory cytokines, oxidative stress, DNA damage and DNA damage response. We demonstrated that the antioxidant defense capacity of Rp-mutant cells is insufficient to meet the greater reactive oxygen species (ROS) production which leads to oxidative DNA damage, cellular senescence and activation of DNA damage response signaling in the developing erythroblasts and altered characteristics of mature erythrocytes. We also showed that the disturbed balance between ROS formation and antioxidant defense is accompanied by the upregulation of proinflammatory cytokines. Finally, the alterations detected in the membrane of DBA erythrocytes may cause their enhanced recognition and destruction by reticuloendothelial macrophages, especially during infections. We propose that the extent of oxidative stress and the ability to activate antioxidant defense systems may contribute to high heterogeneity of clinical symptoms and response to therapy observed in DBA patients.

Impaired cellular and humoral immunity is a feature of Diamond-Blackfan anaemia; experience of 107 unselected cases in the United Kingdom.

Diamond-Blackfan anaemia (DBA) is a rare bone marrow failure syndrome characterised by anaemia, congenital anomalies and cancer predisposition. Although infections are the second leading cause of mortality in non-transplanted patients, immune function is largely unexplored. We identified quantitative deficits in serum immunoglobulins and/or circulating T, natural killer and B lymphocytes in 59 of 107 unselected patients (55·1%) attending our centre over a 7-year period. Immune abnormalities were independent of ribosomal protein genotype and arose in both steroid-treated and steroid-untreated patients. In summary, these data highlight the high prevalence and spectrum of infections and immune defects in DBA.

Innate immune system activation in zebrafish and cellular models of Diamond Blackfan Anemia.

Deficiency of ribosomal proteins (RPs) leads to Diamond Blackfan Anemia (DBA) associated with anemia, congenital defects, and cancer. While p53 activation is responsible for many features of DBA, the role of immune system is less defined. The Innate immune system can be activated by endogenous nucleic acids from non-processed pre-rRNAs, DNA damage, and apoptosis that occurs in DBA. Recognition by toll like receptors (TLRs) and Mda5-like sensors induces interferons (IFNs) and inflammation. Dying cells can also activate complement system. Therefore we analyzed the status of these pathways in RP-deficient zebrafish and found upregulation of interferon, inflammatory cytokines and mediators, and complement. We also found upregulation of receptors signaling to IFNs including Mda5, Tlr3, and Tlr9. TGFb family member activin was also upregulated in RP-deficient zebrafish and in RPS19-deficient human cells, which include a lymphoid cell line from a DBA patient, and fetal liver cells and K562 cells transduced with RPS19 shRNA. Treatment of RP-deficient zebrafish with a TLR3 inhibitor decreased IFNs activation, acute phase response, and apoptosis and improved their hematopoiesis and morphology. Inhibitors of complement and activin also had beneficial effects. Our studies suggest that innate immune system contributes to the phenotype of RPS19-deficient zebrafish and human cells.

Acquired Complement Regulatory Gene Mutations and Hematopoietic Stem Cell Transplant-Related Thrombotic Microangiopathy.

Hematopoietic stem cell transplant-related thrombotic microangiopathy (HSCT-TMA) is a severe complication whose pathophysiology is unknown. We describe 6 patients in which the disease was associated with complement regulatory gene abnormalities received from their respective donors. It is suggested that mutated and transplanted monocyte-derived cells are responsible for production of abnormal proteins, complement dysregulation, and, ultimately, for the disease. This observation might have important drawbacks as far as HSCT-TMA pathophysiology and treatment are concerned.

Late Effects Screening Guidelines after Hematopoietic Cell Transplantation for Inherited Bone Marrow Failure Syndromes: Consensus Statement From the Second Pediatric Blood and Marrow Transplant Consortium International Conference on Late Effects After Pediatric HCT.

Patients with inherited bone marrow failure syndromes (IBMFS), such as Fanconi anemia (FA), dyskeratosis congenita (DC), or Diamond Blackfan anemia (DBA), can have hematologic manifestations cured through hematopoietic cell transplantation (HCT). Subsequent late effects seen in these patients arise from a combination of the underlying disease, the pre-HCT therapy, and the HCT process. During the international consensus conference sponsored by the Pediatric Blood and Marrow Transplant Consortium on late effects screening and recommendations following allogeneic hematopoietic cell transplantation for immune deficiency and nonmalignant hematologic diseases held in Minneapolis, Minnesota in May 2016, a half-day session was focused specifically on the unmet needs for these patients with IBMFS. This multidisciplinary group of experts in rare diseases and transplantation late effects has already published on the state of the science in this area, along with discussion of an agenda for future research. This companion article outlines consensus disease-specific long-term follow-up screening guidelines for patients with IMBFS.

Novel 3q27.2-qter deletion in a patient with Diamond-Blackfan anemia and immunodeficiency: Case report and review of literature.

3q27.2-qter deletion syndromes feature an overlapping set of terminal and interstitial deletions with variable congenital malformations. Diamond-Blackfan anemia (DBA) is etiologically heterogeneous disorder in which one cause is dominant mutations of the RPL35A gene on 3q29. We report a child with a 3q27.2-qter deletion that contains the RPL35A gene. She had clinical and laboratory features consistent with DBA and as well, an unexplained immunodeficiency disorder. Given these unusual findings, we reviewed other patients in the literature with overlapping genomic deletions. In addition, we evaluated our patient for the immunodeficiency disorder, RIDDLE syndrome, due to recessive mutations in the RNF168 gene on 3q29. A PubMed search for case reports of 3q27.2-qter overlapping deletions was performed. To determine if RPL35A was in the deletion region, the chromosomal regions reported were mapped to genomic regions using the UCSC Genome Browser. We identified 85 overlapping deletions, of which six included the RPL35A gene and all should be had DBA. Interestingly, none of the reported cases had immunodeficiency. To evaluate RIDDLE syndrome (radiosensitivity, immunodeficiency, dysmorphic features, and learning difficulties), we sequenced the remaining RNF168 gene and examined her fibroblast culture for a DNA double strand break repair deficiency. These results were normal, indicating that the immunodeficiency is unlikely to result from a RNF168 deficiency. We show that RPL35A haploinsufficiency is a cause of DBA and we report a novel case with 3q27.2-qter deletion and immunodeficiency. The etiology for the immunodeficiency remains unsolved and could be caused by an unknown gene effect or consequent to the DBA phenotype.

Pure red cell aplasia.

Pure red cell aplasia (PRCA) is a syndrome defined by a normocytic normochromic anemia with severe reticulocytopenia and marked reduction or absence of erythroid precursors from the bone marrow. Diamond-Blackfan anemia is a congenital form of PRCA. Acquired PRCA may be either a primary disorder or secondary to some other disorder or agent. Primary acquired PRCA is an autoimmune disorder that is frequently antibody-mediated. Myelodysplastic syndromes may also present with the morphologic appearance of PRCA. Secondary acquired PRCA may be associated with collagen vascular/autoimmune disorders such as systemic lupus erythematosus; lymphoproliferative disorders such as chronic lymphocytic leukemia or large granular lymphocyte leukemia; infections, particularly B19 parvovirus; thymoma and other solid tumors; or a variety of other disorders, drugs, or toxic agents. The therapeutic approach to PRCA typically involves immunosuppression, but specific pathogenic subtypes are associated with specific therapeutic approaches. Cyclosporine A, with or without concurrent corticosteroids, appears to be the single most effective immunosuppressive agent.

Pure red cell aplasia.

Pure red cell aplasia (PRCA) is a syndrome defined by a normocytic normochromic anemia with severe reticulocytopenia and marked reduction or absence of erythroid precursors from the bone marrow. Diamond-Blackfan anemia is a congenital form of PRCA. Acquired PRCA may be either a primary disorder or secondary to some other disorder or agent. Primary acquired PRCA is an autoimmune disorder that is frequently antibody-mediated. Myelodysplastic syndromes may also present with the morphologic appearance of PRCA. Secondary acquired PRCA may be associated with collagen vascular/autoimmune disorders such as systemic lupus erythematosus; lymphoproliferative disorders such as chronic lymphocytic leukemia or large granular lymphocyte leukemia; infections, particularly B19 parvovirus; thymoma and other solid tumors; or a variety of other disorders, drugs, or toxic agents. The therapeutic approach to PRCA typically involves immunosuppression, but specific pathogenic subtypes are associated with specific therapeutic approaches. Cyclosporine A, with or without concurrent corticosteroids, appears to be the single most effective immunosuppressive agent.

Immune status of patients with inherited bone marrow failure syndromes.

Immune function abnormalities have been reported in patients with Fanconi anemia (FA), dyskeratosis congenita (DC) and, rarely, in Shwachman-Diamond syndrome (SDS), and Diamond-Blackfan anemia (DBA), but large systematic studies are lacking. We assessed immunological parameters in 118 patients with these syndromes and 202 unaffected relatives. We compared the results in patients with reference values, and with values in relatives after adjusting for age, sex, corticosteroid treatment, and severe bone marrow failure (BMF). Adult patients (≥18 years) with FA had significantly lower immunoglobulins (IgG, IgA and IgM), total lymphocytes, and CD4 T cells than reference values or adult relatives (P < 0.001); children with FA had normal values. Both children and adults with FA had lower B- and NK cells (P < 0.01) than relatives or reference values. Patients with DC had essentially normal immunoglobulins but lower total lymphocytes than reference values or relatives, and lower T-, B-, and NK-cells; these changes were more marked in children than adults (P < 0.01). Most patients with DBA and SDS had normal immunoglobulins and lymphocytes. Lymphoproliferative responses, serum cytokine levels, including tumor necrosis factor-α and interferon-γ, and cytokine levels in supernatants from phytohemagglutinin-stimulated cultures were similar across patient groups and relatives. Only patients with severe BMF, particularly those with FA and DC, had higher serum G-CSF and Flt3-ligand and lower RANTES levels compared with all other groups or relatives (P < 0.05). Overall, immune function abnormalities were seen mainly in adult patients with FA, which likely reflects their disease-related progression, and in children with DC, which may be a feature of early-onset severe disease phenotype.

A novel reduced-intensity conditioning regimen for unrelated umbilical cord blood transplantation in children with nonmalignant diseases.

Reduced-intensity conditioning (RIC) regimens have the potential to decrease transplantation-related morbidity and mortality. However, engraftment failure has been prohibitively high after RIC unrelated umbilical cord blood transplantation (UCBT) in chemotherapy-naïve children with nonmalignant diseases (NMD). Twenty-two children with a median age of 2.8 years, many with severe comorbidities and prior viral infections, were enrolled in a novel RIC protocol consisting of hydroxyurea, alemtuzumab, fludarabine, melphalan, and thiotepa followed by single UCBT. Patients underwent transplantation for inherited metabolic disorders (n = 8), primary immunodeficiencies (n = 9), hemoglobinopathies (n = 4) and Diamond Blackfan anemia (n = 1). Most umbilical cord blood (UCB) units were HLA-mismatched with median infused total nucleated cell dose of 7.9 × 10(7)/kg. No serious organ toxicities were attributable to the regimen. The cumulative incidence of neutrophil engraftment was 86.4% (95% confidence interval [CI], 65% to 100%) in a median of 20 days, with the majority sustaining > 95% donor chimerism at 1 year. Cumulative incidence of acute graft-versus-host disease (GVHD) grades II to IV and III to IV by day 180 was 27.3% (95% CI, 8.7% to 45.9%) and 13.6% (95 CI, 0% to 27.6%), respectively. Cumulative incidence of extensive chronic GVHD was 9.1% (95% CI, 0% to 20.8%). The primary causes of death were viral infections (n = 3), acute GVHD (n = 1) and transfusion reaction (n = 1). One-year overall and event-free survivals were 77.3% (95% CI, 53.7% to 89.8%) and 68.2% (95% CI, 44.6% to 83.4%) with 31 months median follow-up. This is the first RIC protocol demonstrating durable UCB engraftment in children with NMD. Future risk-based modifications of this regimen could decrease the incidence of viral infections. (www.clinicaltrials.gov/NCT00744692).