Immunosuppressive treatment of aplastic anemia with antithymocyte globulin and cyclosporine

Treatment of newly diagnosed severe aplastic anemia in children: Evidence-based recommendations

Severe aplastic anemia (SAA) is a rare potentially fatal hematologic disorder. Although overall outcomes with treatment are excellent, there are variations in management approach, including differences in treatment between adult and pediatric patients. Certain aspects of treatment are under active investigation in clinical trials. Because of the rarity of the disease, some pediatric hematologists may have relatively limited experience with the complex management of SAA. The following recommendations reflect an up-to-date evidence-based approach to the treatment of children with newly diagnosed SAA.

Relapse and transformation to myelodysplastic syndrome and acute myeloid leukemia following immunosuppressive therapy for aplastic anemia is more common as compared to allogeneic stem cell transplantation with a negative impact on survival

We studied the incidence of relapse, transformation to myelodysplastic syndrome/acute myeloid leukemia, and survival in patients with aplastic anemia (AA) surviving more than 1 year after ATG/ALG-based immunosuppressive therapy (IST) between 1985 and 2020. Four-hundred seventy patients (413 adults and 57 children) were studied, and data were compared with 223 patients who underwent matched sibling donor transplant (MSD HSCT). Median follow-up is 50 months (12-359). Relapse occurred in 21.9% at a median time of 33.5 months (5-228) post IST. Twenty-six (5.5%) patients progressed to PNH, while 20 (4.3%) evolved to MDS/AML. Ten-year estimated overall survival (OS) is 80.9 ± 3% and was significantly better in patients without an event (85.1 ± 4%) compared to relapse (74.6% ± 6.2%) or clonal evolution (12.8% ± 11.8%) (p = 0.024). While the severity of AA (p = 0.011) and type of ATG (p = 0.028) used predicted relapse, only age at IST administration influenced clonal evolution (p = 0.018). Among HSCT recipients, relapse rates were 4.9% with no clonal evolution, and the 10-year OS was 94.5 ± 2%. In patients who survived 1 year following IST, outcomes were good except with clonal evolution to MDS/AML. These outcomes, however, were still inferior compared to matched sibling donor HSCT.

A Case of Aplastic Anemia Complicated With Cerebral Infarction

Aplastic anemia is usually associated with hemorrhagic stroke. Here, we report a case of ischemic stroke secondary to aplastic anemia in a 28-year-old male who presented with sudden-onset right hemiplegia and aphasia when he was not on any immunosuppression for five months. His laboratory findings showed pancytopenia, and his peripheral blood smear showed no atypical cells. Magnetic resonance imaging of the brain with magnetic resonance angiography (MRA) of the neck and brain vessels revealed an infarct in the left cerebral hemisphere in the middle cerebral artery territory, and no significant stenosis or aneurysm was observed on MRA. The patient was managed conservatively and discharged in stable condition.

Population Pharmacokinetics of Cyclosporine in Chinese Pediatric Patients With Acquired Aplastic Anemia

Cyclosporine (CsA) is a component of the first-line treatment for acquired aplastic anemia (acquired AA) in pediatric patients. This study aimed to develop a population pharmacokinetic (PK) model of CsA in Chinese pediatric patients with acquired AA to inform individual dosage regimens. A total of 681 CsA whole blood concentrations and laboratory data of 157 pediatric patients with acquired AA were retrospectively collected from two hospitals in Shanghai. A nonlinear mixed-effect model approach was used to build the population PK model. Potential covariate effects of age, body weight, and biochemical measurements (renal and liver functions) on CsA PK disposition were evaluated. Model fit was assessed using the basic goodness of fit and a visual predictive check. The CsA concentration data were accurately described using a two-compartment disposition model with first-order absorption and elimination. Body weight value was implemented as a fixed allometric function on all clearance and volume of distribution parameters. Total bilirubin level was identified as a significant covariate on apparent clearance (CL/F), with a 1.07% reduction per 1 nmol/L rise in total bilirubin level. The final estimates for CL/F and central volume (Vc/F) were 29.1 L/h and 325 L, respectively, for a typical 28 kg child. Other covariates (e.g., gender, age, albumin, hemoglobin, hematocrit, serum creatinine, and concomitant medication) did not significantly affect the PK properties of CsA. This population PK model, along with a maximum a posteriori Bayesian approach, could estimate individual PK parameters in pediatric patients with acquired AA to conduct individual CsA therapy.

The Role of T Lymphocytes in the Pathogenesis of Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem cell genetic mutation disease that causes defective erythrocyte membrane hemolysis. Its pathologic basis is the mutation of the PIG-A gene, whose product is necessary for the synthesis of glycosylphosphatidylinositol (GPI) anchors; the mutation of PIG-A gene results in the reduction or deletion of the GPI anchor, which leads to the deficiency of GPI-anchored proteins (GPI-APs), such as CD55 and CD59, which are complement inhibitors. The deficiency of complement inhibitors causes chronic complement-mediated intravascular hemolysis of GPI-anchor-deficient erythrocyte. PIG-A gene mutation could also be found in bone marrow hematopoietic stem cells (HSCs) of healthy people, but they have no growth advantage; only the HSCs with PIG-A gene mutation in PNH patients have this advantage and expand. Besides, HSCs from PIG-A-knockout mice do not show clonal expansion in bone marrow, so PIG-A mutation cannot explain the clonal advantage of the PNH clone and some additional factors are needed; thus, in recent years, many scholars have put forward the theories of the second hit, and immune escape theory is one of them. In this paper, we focus on how T lymphocytes are involved in immune escape hypothesis in the pathogenesis of PNH.

Pediatric bone marrow failure: Clinical, hematological and targeted next generation sequencing data

OBJECTIVE

In this study, clinico-hematological, genetic and outcome profile of children with BMF was evaluated to delineate the underlying genotype and phenotype.

DESIGN

Cases were evaluated as two groups: Group 1 (n = 56; DBA-23, FA-18, DC-2, UBMFS-13) included children with suspected IBMFS based on clinical phenotype and accessible lab investigations and Group 2 (n = 53) included children with IAA treated with IST. Targeted NGS was carried out in a subset of these children (n = 42) and supplemented with WES wherever required.

RESULTS

We identified causative mutation in overall 15 of 27 tested children (55.5%) in group 1 and 2 of 15 tested children (13.3%) in group 2. In DBA, a mutation was noted in 50% cases with involvement of RPS 19 (75%) and RPL5 (25%) genes. Phenotypic abnormalities were present in 69.5% and response to steroids in 68.4% of cases at a median follow up of 33 months. In children with IAA, overall response (complete + partial) was present in 51% at a median follow up of 23 months. The 3-year OS and FFS for the cohort of IAA were 68% and 48% respectively. Targeted sequencing could also pick up germline mutations in 50% of UBMFS cases and nearly 19% of IAA cases.

Recent Advances and Long-Term Results of Medical Treatment of Acquired Aplastic Anemia: Are Patients Cured?

Horse antithymocyte globulin plus cyclosporine remains standard immunosuppressive therapy in severe aplastic anemia, with hematologic response rates of 60% to 70%. In those refractory to this regimen, a second course of therapy with rabbit antithymocyte globulin plus cyclosporine or alemtuzumab produces responses in 30% to 40%. Eltrombopag, a thrombopoietin receptor agonist, showed activity as a single agent in those refractory to initial immunosuppression with hematologic response rates of 40% to 50%. When combined with immunosuppression as frontline therapy, eltrombopag increased the rate of overall and complete response rates. Longer follow-up is needed to better define these outcomes.

Human embryonic stem cell therapy for aplastic anemia

Human embryonic stem cell (hESC) therapy is the potential therapeutic option for the treatment of patients with aplastic anemia (AA). The study showed a remarkable improvement in the AA patient subsequent to hESC administration. No adverse events occurred in the patient. hESC therapy is safe and effective for AA patients.

[Delayed hematologic response to immunosuppressive therapy in severe aplastic anemia]

Objective: To explore the characteristics of delayed hematologic response in very/severe aplastic anemia (V/SAA) patients who were treated with immunosuppressive treatment (IST) as first-line approach, and investigate the rationality of early salvage treatment in refractory patients. Methods: The data of V/SAA patients front-line treated with IST were retrospectively analyzed. Delayed response was defined as acquiring hematologic response between 6 and 12 months after 1 course of IST. The clinical as well as hematologic characteristics of the delayed responded patients were investigated. Results: Of the 533 patients, 45 (8.44%, 45/533) were delayed hematologic responders, which accounted for 29.03% (45/155) of the whole non-responders at 6 months. The quality of response in delayed responders analyzed at 12 months (χ2=62.616, P <0.001) and at the end of follow-up (χ2=6.299, P=0.043) was significantly worse than that of robust response group. There were more VSAA patients in delayed response group compared with robust response group (57.8% vs 38.3%, P=0.013), and all the baseline absolute reticulocyte (ARC) count, ARC proportion and absolute neutrophil count (ANC) were much lower than that in delayed response group. Multivariate analysis about the above 2 groups showed that the baseline ARC count <10×109/L significanty reduced the chance of hematologic response within 6 months [OR=3.641(95% CI 1.718-7.719) , P=0.001], and not any factor was found to predict delayed hematologic response in non-responders at 6 months. The 5-year overall survival of 76.50% (95% CI 71.6%-81.4%) and event free survival of 29.10%(95% CI 25.2%-33.0% ) in non-responders at 6 months, both were worse than 97.6% (95% CI 96.6%-98.6% ) and 84.0% (95% CI 81.1%-86.9% ) (P <0.001) of robust response group. Conclusion: The incidence of delayed hematologic response in V/SAA patients by IST is low. The quality of delayed response is not satisfactory and there is no effective means to predict the delayed response. It is reasonable to carry out salvage treatment as early as possible.

Impaired Autophagy in Adult Bone Marrow CD34+ Cells of Patients with Aplastic Anemia: Possible Pathogenic Significance

Aplastic anemia (AA) is a bone marrow failure syndrome that is caused largely by profound quantitative and qualitative defects of hematopoietic stem and progenitor cells. However, the mechanisms underlying these defects remain unclear. Under conditions of stress, autophagy acts as a protective mechanism for cells. We therefore postulated that autophagy in CD34⁺ hematopoietic progenitor cells (HPCs) from AA patients might be impaired and play a role in the pathogenesis of AA. To test this hypothesis, we tested autophagy in CD34⁺ cells from AA samples and healthy controls and investigated the effect of autophagy on the survival of adult human bone marrow CD34⁺ cells. We found that the level of autophagy in CD34⁺ cells from AA patients was significantly lower than in age/sex-matched healthy controls, and lower in cases of severe AA than in those with non-severe AA. Autophagy in CD34⁺ cells improved upon amelioration of AA but, compared to healthy controls, was still significantly reduced even in AA patients who had achieved a complete, long-term response. We also showed that although the basal autophagy in CD34⁺ cells was low, the autophagic response of CD34⁺ cells to “adversity” was rapid. Finally, impaired autophagy resulted in reduced differentiation and proliferation of CD34⁺ cells and sensitized them to death and apoptosis. Thus, our results confirm that autophagy in CD34⁺ cells from AA patients is impaired, that autophagy is required for the survival of CD34⁺ cells, and that impaired autophagy in CD34⁺ HPCs may play an important role in the pathogenesis of AA.

Model-Based Determination of Effective Blood Concentrations of Cyclosporine for Neutrophil Response in the Treatment of Severe Aplastic Anemia in Children

Optimal immunosuppressive therapy in acquired severe aplastic anemia (SAA) remains to be refined, especially cyclosporine (CsA) use. Current recommendations state that CsA trough blood concentrations (TBC) should be maintained between 200 and 400 ng/mL despite the lack of supporting data. This study aimed at quantifying relationships between CsA exposure and neutrophil response and determining an effective range for CsA TBC. Twenty-three SAA patients treated with CsA were retrospectively analyzed. Nonlinear mixed effect modeling approaches were used to develop a pharmacokinetic-pharmacodynamic model. The pharmacokinetic model described the relationships between CsA doses and TBC. The pharmacodynamic model allowed to estimate boundaries for optimal CsA effects, neutrophils being used as biomarker of response. A time-to-event model linked effective concentration to time-to-therapeutic success. CsA TBC were adequately described by a two-compartment model with first-order absorption, a lag time, and a linear elimination. The efficient range of CsA TBC was estimated between 87 and 120 ng/mL. Model-based simulations and external validation in three additional patients confirmed these results. This original modeling approach was successful in describing the relationship between CsA TBC and neutrophil response in SAA patients. Although further evaluation of the model is necessary, this work suggests that an optimal CsA TBC target of 100 ng/mL would be associated with a better neutrophil response in children with SAA.

Increased immunosuppressive treatment combined with unrelated umbilical cord blood infusion in children with severe aplastic anemia

A combination treatment of unrelated umbilical cord blood (UCB) and increased immunosuppressive treatment (IST) were investigated to reveal the potentially curative therapy for the severe aplastic anemia (SAA). A total of 36 children (2-17 ages) with SAA who received UCB infusion after an IST were analyzed. The treatment consisted of 100mg/kg cyclophosphamide, 12.5-15 mg/kg antithymocyte globulin and 3mg/kg cyclosporine. After 3 months, the hematologic complete response (CR) rate was 22.2% and partial response (PR) rate was 38.9%. After 6 months, the CR rate and PR rate was 50.4% and 26.3%, respectively. The probability of 3-year survival was 83.3%. There was no difference in the survival rate either between the horse-ATG and rabbit-ATG or between the SAA and VSAA. The results indicated that the increased IST combined with unrelated UCB infusion has an effective therapeutic potential for children with SAA who lack of compatible donor for transplantation.

Antithymocyte globulin/antilymphocyte globulin plus kidney-nourishing Chinese medicinal: effect on severe aplastic anemia

OBJECTIVE

To explore the effect of antithymocyte globulin (ATG)/antilymphocyte globulin (ALG) plus kidney-nourishing Chinese medicinal (KNCM) on severe aplastic anemia (SAA).

METHODS

Twenty-five subjects of severe aplastic anemia were treated with ATG/ALD plus KNCM between 1992 and 2009, and the clinical data before and after treatment were collected and analyzed.

RESULTS

Of the 25 patients, 9 were nearly cured, 6 were improved, 5 were in remission, and 5 failed. The overall effective rate was 80.0%. The 3-year, 5-year, 10-year, 15-year survival rate were respectively 98.6%, 97.3%, 97.3%, 67.5%, and median survival time was 180 months. Compared to the conditions before administering the medication of ATG/ ALG plus KNCM, after 2 weeks, reticulocyte was first improved (P = 0.001); one month later, followed by palette (P = 0.037); two months later, by neutrophil cell in peripheral blood (P = 0.001); three months later, then by the hemoglobin (P = 0.012). By conducting 1-year follow-up, 1 case of complication--paroxysmal nocturnal hemoglobinuria (PNH) was identified and the patient still alive today.

CONCLUSION

ATG/ALG plus KNCM had better effect on SAA and could improve patients' survival rate.

Immunosuppressive therapy in aplastic anemia

OBJECTIVE

To assess the response to antithymocyte globulin based immunosuppressive therapy (IST) in pediatric patients with idiopathic aplastic anemia.

METHODS

Thirty patients (19 boys and 11 girls) with aplastic anemia received antithymocyte globulin and cyclosporine. Twenty-two patients had severe and 8 had very severe aplastic anemia.

RESULTS

Mean age of the patients was 9.19 ± 2.56 y. Three patients died within 1 mo of therapy, two due to sepsis and one due to intracranial hemorrhage. Twenty-seven patients were analyzed for response to therapy. Eight patients (29.7%) responded at 3 mo: 3 complete response (CR) and 5 partial response (PR). Six mo after the therapy, overall response (OR) was seen in 9/27 (33.3%), with one more patient in no response group achieving partial response. At 1 year, patients in CR maintained their status and 1 patient in PR group relapsed. He again achieved partial response with repeat course of ATG. Responders had significantly shorter duration of illness and higher absolute neutrophil count as compared to non responders to IST. None of the patients developed acute leukemia in the follow up.

CONCLUSIONS

The treatment of aplastic anemia in pediatric patients is a challenging task. One third of the patients achieved overall response which included both complete and partial response.

Hydrogen therapy may be an effective and specific novel treatment for aplastic anemia

Aplastic anemia (AA) is a rare bone marrow failure disorder with high mortality rate, which is characterized by pancytopenia and an associated increase in the risk of hemorrhage, infection, organ dysfunction and death. The oxidation phenomenon and/or the formation of free radicals have been suggested to be causally related to various hematological disorders, including aplastic anemia. TNF-α, IL-6, and IL-2 also play important roles in the pathogenesis of AA. Recent studies have provided evidence that hydrogen inhalation can selectively reduce cytotoxic oxygen radicals and exert antioxidant effects. It was also reported that hydrogen could suppress the levels of TNF-α and IL-6. Based on these findings, we hypothesize that hydrogen therapy may be an effective, simple, economic and novel strategy in the treatment of aplastic anemia.

Activity of alemtuzumab monotherapy in treatment-naive, relapsed, and refractory severe acquired aplastic anemia

Antithymocyte globulin (ATG) + cyclosporine is effective in restoring hematopoiesis in severe aplastic anemia (SAA). We hypothesized that the humanized anti-CD52 mAb alemtuzumab might be active in SAA because of its lymphocytotoxic properties. We investigated alemtuzumab monotherapy from 2003-2010 in treatment-naive, relapsed, and refractory SAA in 3 separate research protocols at the National Institutes of Health. Primary outcome was hematologic response at 6 months. For refractory disease, patients were randomized between rabbit ATG + cyclosporine (n = 27) and alemtuzumab (n = 27); the response rate for alemtuzumab was 37% (95% confidence interval [CI], 18%-57%) and for rabbit ATG 33% (95% CI, 14%-52%; P = .78). The 3-year survival was 83% (95% CI, 68%-99%) for alemtuzumab and 60% (95% CI, 43%-85%) for rabbit ATG (P = .16). For relapsed disease (n = 25), alemtuzumab was administered in a single-arm study; the response rate was 56% (95% CI, 35%-77%) and the 3-year survival was 86% (95% CI, 72%-100%). In treatment-naive patients (n = 16), alemtuzumab was compared with horse and rabbit ATG in a 3-arm randomized study; the response rate was 19% (95% CI 0%-40%), and the alemtuzumab arm was discontinued early. We conclude that alemtuzumab is effective in SAA, but best results are obtained in the relapsed and refractory settings. The present trials were registered at www.clinicaltrials.gov as NCT00195624, NCT00260689, and NCT00065260.

Survival after immunosuppressive therapy in children with aplastic anemia

OBJECTIVE

To determine the survival of children =18 y, treated with immunosuppressive therapy (IST) using equine antithymocyte globulin (e-ATG) and cyclosporine (CsA).

DESIGN

Prospective data entry as per a specified format.

SETTING

Tertiary care hospital.

PATIENTS

From January 1998 to December 2009, 40 children were diagnosed with acquired aplastic anemia; 33 patients, who received IST, were analyzed. 31 children (94%) received one course of e-ATG and CsA. 2 patients (6%) received two courses of ATG.

INTERVENTION

Immunosuppressive therapy using equine ATG and cyclosporine.

MAIN OUTCOME MEASURES

Overall response and overall survival.

RESULTS

The overall response (complete response + partial response) to IST at 6 months was 87.9%. 8 (24.2%) patients achieved CR, 21 (63.6%) patients had PR and 4 (12.1%) patients did not respond to IST. Median follow-up was 24 (6-102) months. Overall survival at 24 months was 90%, with an actual survival of 85.4% at 5 years. Seventeen patients (51.5%) received G-CSF for a median duration of 32 (23-64) days. The patients who received G-CSF had fewer infectious complications (P=0.002), but G-CSF administration did not influence survival/ outcome. No patient developed myelodysplastic syndrome or acute leukemia.

CONCLUSIONS

The survival of patients who respond to IST is excellent. Also, G-CSF reduces the infectious complications without conferring any survival advantage.

Rabbit antithymocyte globulin (thymoglobulin): 25 years and new frontiers in solid organ transplantation and haematology

The more than 25 years of clinical experience with rabbit antithymocyte globulin (rATG), specifically Thymoglobulin, has transformed immunosuppression in solid organ transplantation and haematology. The utility of rATG has evolved from the treatment of allograft rejection and graft-versus-host disease to the prevention of various complications that limit the success of solid organ and stem cell transplantation. Today, rATG is being successfully incorporated into novel therapeutic regimens that seek to reduce overall toxicity and improve long-term outcomes. Clinical trials have demonstrated the efficacy and safety of rATG in recipients of various types of solid organ allografts, recipients of allogeneic stem cell transplants who are conditioned with both conventional and nonconventional regimens, and patients with aplastic anaemia. Over time, clinicians have learnt how to better balance the benefits and risks associated with rATG. Advances in the understanding of the multifaceted mechanism of action will guide research into new therapeutic areas and future applications.

Influence of nucleated cell dose on overall survival of unrelated cord blood transplantation for patients with severe acquired aplastic anemia: a study by eurocord and the aplastic anemia working party of the European group for blood and marrow transplantation

Information is scarce on outcomes after unrelated cord blood transplantation (UCBT) for patients with severe aplastic anemia (SAA). We retrospectively analyzed 71 patients (median age, 13 years; 28 adults) with SAA (9 with paroxysmal nocturnal hemoglobinuria [PNH]) who received a single-unit (n = 57; 79%) or double-unit UCBT (n = 14; 19%) in 32 centers between 1996 and 2009. A reduced-intensity conditioning regimen was provided in 68% of the patients. The cumulative incidence (CI) of neutrophil recovery was 51% ± 6% at day 60, with significantly better engraftment seen in recipients of higher prefreezing total nucleated cell (TNC) dose (>3.9 10(7)/kg; hazard ratio [HR], 1.5; P = .05). The CI of platelet engraftment at day 180 posttransplantation was 37% ± 7%, that of grade II-IV acute GVHD was 20% ± 5%, and that of chronic GVHD at 3 years was 18% ± 5%. At a median follow-up of 35 months (range, 3-83 months), the estimated probability of 3-year overall survival (OS) was 38% ± 6%. Significantly improved OS was seen in recipients of >3.9 10(7) TNCs/kg prefreezing (45%, compared with 18% for recipients of ≤ 3.9 10(7) TNC/kg; HR, 0.4; P = .007). These results highlight the fundamental role of cell dose for both engraftment and OS in patients with SAA undergoing UCBT.

The role of the Th1 transcription factor T-bet in a mouse model of immune-mediated bone-marrow failure

The transcription factor T-bet is a key regulator of type 1 immune responses. We examined the role of T-bet in an animal model of immune-mediated bone marrow (BM) failure using mice carrying a germline T-bet gene deletion (T-bet(-/-)). In comparison with normal C57BL6 (B6) control mice, T-bet(-/-) mice had normal cellular composition in lymphohematopoietic tissues, but T-bet(-/-) lymphocytes were functionally defective. Infusion of 5 x 10(6) T-bet(-/-) lymph node (LN) cells into sublethally irradiated, major histocompatibility complex-mismatched CByB6F1 (F1) recipients failed to induce the severe marrow hypoplasia and fatal pancytopenia that is produced by injection of similar numbers of B6 LN cells. Increasing T-bet(-/-) LN-cell dose to 10 to 23 x 10(6) per recipient led to only mild hematopoietic deficiency. Recipients of T-bet(-/-) LN cells had no expansion in T cells or interferon-gamma-producing T cells but showed a significant increase in Lin(-)Sca1(+)CD117(+)CD34(-) BM cells. Plasma transforming growth factor-beta and interleukin-17 concentrations were increased in T-bet(-/-) LN-cell recipients, possibly a compensatory up-regulation of the Th17 immune response. Continuous infusion of interferon-gamma resulted in hematopoietic suppression but did not cause T-bet(-/-) LN-cell expansion or BM destruction. Our data provided fresh evidence demonstrating a critical role of T-bet in immune-mediated BM failure.

Aplastica anemia and viral hepatitis

Acquired aplastic anemia (aAA) is a severe and rare disease, characterized by hematopoietic bone marrow failure and peripheral cytopenia. The pathophysiology is immune mediated in most cases, activated T1 lymphocytes have been identified as effector cells. The disease can be successfully treated with combined immunosuppressive therapy or allogeneic hematopoietic stem cell transplantation. Hepatitis-associated aplastic anemia (HAA) is a syndrome of bone marrow failure following the development of acute seronegative hepatitis. HAA syndrome most often affects young males who presented severe pancytopenia two to three months after an episode of acute hepatitis. The clinical course of hepatitis is more frequently benign but a fulminant severe course is also described. The bone marrow failure can be explosive and severe and it is usually fatal if untreated, no correlations have been observed between severity of hepatitis and AA. In none of the studies a specific virus could be identified and most cases are seronegative for known hepatitis viruses. The clinical characteristics and response to immunotherapy indicate a central role for immune-mediated mechanism in the pathogenesis of HAA. The initial target organ of the immune response is the liver as suggested by the time interval between hepatitis and the onset of bone marrow failure. Liver histology is characterized by T cell infiltrating the parenchyma as reported in acute hepatitis. Recently in HAA it has been demonstrated intrahepatic and blood lymphocytes with T cell repertoire similar to that of confirmed viral acute hepatitis. The expanded T cell clones return to a normal distribution after response to immunosuppressive treatment, suggesting the antigen or T cell clearance. Therapeutic options are the same as acquired aplastic anemia.

A hospital-based case control study of aplastic anemia in Shanghai, China

We report results of a hospital-based case control study of 137 consecutive patients diagnosed with aplastic anemia (AA) in participating hospitals over a 4-year period. Diagnoses were made by a single laboratory, subjects were age- and gender-matched to two controls and interviewed concerning previous disease, work histories and exposures to potential etiologic agents. Analysis was conducted on two distinct subgroups: severe aplastic anemia (SAA) and moderate aplastic anemia (MAA). In univariate regression models, the strongest associations were observed for exposure to benzene and SAA (OR=3.12, 95% CI=1.12-8.65) and life on a farm and MAA (OR=3.08, 95% CI=1.44-6.56). Benzene exposure did not show a strong dose-response relationship with either subtype. When accounting for all of the potential confounders we considered in conditional regression models, the previous relationships persisted. Other explanatory variables included hair-dye use for MAA and farm exposures, such as livestock for SAA, although most of these additional variables fell just short of statistical significance. Adjusted R-squared values were only 10% for each subtype, leaving 90% of AA occurrence unexplained. Our results suggest that: (a) benzene exposure is more strongly related to SAA than MAA, (b) farm and livestock exposures are related to both forms of AA, confirming some previous results, and (c) a large percentage of AA remains unexplained, which may indicate that individual susceptibility has a major influence on AA occurrence.

Acquired immune mediated aplastic anemia: is it antineoplastic?

There is increasing evidence that autoimmunity can inhibit growth of solid tumors. We propose that anti-tumor activity also operates in autoimmunity against hematopoietic stem cells in acquired aplastic anemia (AA). Reduction/dysfunction of regulatory T cells (T(REG)) in AA - rather than being the primary event - could be a response to insufficient or failing anti-tumor reactivity in predisposed individuals, causing elimination of tumor cells and collateral damage to adjacent normal hematopoietic tissue. This pathophysiological mechanism could also apply to otherwise unexplained pancytopenic syndromes which frequently occur in patients with leukemia and lymphoma and non-hematological malignancies. Observations supporting an anti-tumor effect of marrow hypoplasia/aplasia are presented and illustrated with case reports. The conclusion would be that pancytopenia occurring in AA or in AA-like syndromes reflects an ongoing immune reaction against underlying malignancy or infection.

Long-term outcome of pediatric patients with severe aplastic anemia treated with antithymocyte globulin and cyclosporine

OBJECTIVE

To determine the long-term outcomes in children with severe aplastic anemia (SAA) treated with antithymocyte globulin (ATG) and cyclosporine (CsA) through a retrospective analysis of the pediatric patients treated at our institution in all protocols that included horse ATG (h-ATG) and CsA.

STUDY DESIGN

Between 1989 and 2006, a total of 406 patients, 20% of whom were children under age 18 years, received an initial course of immunosuppressive therapy (IST) at our institution. Here we report the outcome of 77 children who were treated with an h-ATG plus CsA-based regimen during this period.

RESULTS

The overall response rate at 6 months was 74% (57/77); the cumulative incidence of relapse at 10 years was 33%, and the median time to relapse was 558 days. The cumulative incidence of evolution after IST was 8.5%; all 3 such events occurred in partial responders. Overall, there were 13 deaths (17%), with 4 occurring within the 3 months after IST in patients who had a pretreatment absolute neutrophil count of < 100/microL and the other 9 occurring more than 6 months after initiation of IST. The median time to death was 570 days. The overall 10-year survival for the entire cohort was 80%; long-term survival in the children who responded to IST was 89%.

CONCLUSIONS

The long-term survival in pediatric patients who respond to IST is excellent, at about 90%. IST remains a good alternative in pediatric patients who lack an HLA-matched sibling donor and should be offered as initial therapy before possible hematopoietic stem cell transplantation from an unrelated donor.

Predicting response to immunosuppressive therapy and survival in severe aplastic anaemia

Horse anti-thymocyte globulin (h-ATG) and ciclosporin are the initial therapy for most patients with severe aplastic anaemia (SAA), but there is no practical and reliable method to predict response to this treatment. To determine whether pretreatment blood counts discriminate patients with SAA who have a higher likelihood of haematological response at 6 months to immunosuppressive therapy (IST), we conducted a single institution retrospective analysis on 316 SAA patients treated with h-ATG-based IST from 1989 to 2005. In multivariate analysis, younger age, higher baseline absolute reticulocyte count (ARC), and absolute lymphocyte count (ALC) were highly predictive of response at 6 months. Patients with baseline ARC > or = 25 x 10(9)/l and ALC > or = 1 x 10(9)/l had a much greater probability of response at 6 months following IST compared to those with lower ARC and ALC (83% vs. 41%, respectively; P < 0.001). This higher likelihood of response translated to greater rate of 5-year survival in patients in the high ARC/ALC group (92%) compared to those with a low ARC/ALC (53%). In the era of IST, the baseline ARC and ALC together serve as a simple predictor of response following IST, which should guide in risk stratification among patients with SAA.

Aplastic anemia

PURPOSE OF REVIEW

Most acquired aplastic anemia is the result of immune-mediated destruction of hematopoietic stem cells causing pancytopenia and an empty bone marrow, which can be successfully treated with either immunosuppressive therapy or hematopoietic stem-cell transplantation.

RECENT FINDINGS

In aplastic anemia, oligoclonally expanded cytotoxic T cells induce apoptosis of hematopoietic progenitors. T-bet, a transcription factor that binds to the interferon-gamma promoter region, is upregulated in aplastic anemia T cells. Regulatory T cells are significantly reduced in patients' peripheral blood and in an aplastic anemia murine model, infusion of regulatory T cells ameliorates disease progression. In a minority of cases, loss-of-function mutations in telomerase complex genes may underlie disease development. Long-term survival, once strongly linked to response to immunosuppressive therapy, can now be achieved even among nonresponders due to significant advances in supportive care and better salvage treatments.

SUMMARY

Evidence has accumulated in the recent years further corroborating an immune-mediated process underlying aplastic anemia pathogenesis. Hematopoietic stem-cell transplantation from a matched sibling donor is preferred for children and young adults with severe aplastic anemia, and immunosuppressive therapy is employed when hematopoietic stem-cell transplantation is not feasible due to age, lack of a histocompatible sibling, co-morbidities, or by patient choice.

Outcome of children with aplastic anemia treated with immunosuppressive therapy

BACKGROUND

Immunosuppressive therapy (IST) is the alternative treatment in children with aplastic anemia (AA) who do not have an HLA-matched sibling. The aim of this study is to evaluate the outcome of children with AA treated with IST.

METHODS

We retrospectively reviewed the hospital records of children with AA from 1984 to 2004, treated at our institution with antithymocyte globulin (ATG), cyclosporine (CS), and short course of prednisone.

RESULT

Forty-two patients were treated with IST (24 boys, 18 girls); of whom 26% received G-CSF. The median age at diagnosis was 8.5 years. Sixty-nine, 19, and 12% were diagnosed with severe, very severe, and moderate AA, respectively. Twenty-one percent had hepatitis-associated AA. Median follow-up time was 53.3 months. Sixty-two percent had complete response; 19% had partial response. Two patients relapsed and received a second course of ATG; both had a partial response. The actuarial 5 years survival rate was 67.5%. Two patients developed myelodysplastic syndrome (MDS); both received long-term G-CSF and had partial response after two courses of IST. Fifteen percent of survivors had significant hypertension which persisted after CS was discontinued.

CONCLUSIONS

This study shows promising response in children with AA treated with IST; however, the outcome was inferior to our institutional results with hematopoietic stem cell transplantation from a sibling donor. Hypertension and MDS are late complications. Longer follow-up, larger cohorts, and prospective studies are warranted to evaluate late complications and risk factors.

Autoimmunity and malignancy in hematology—More than an association

Several associations between hematological malignancies and autoimmunity directed against hematopoietic cells exist. Antibody mediated elimination of mature blood cells such as autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP) are frequent complications of non-Hodgkin lymphomas, most prominently chronic lymphocytic leukemia. Autoimmunity directed against hematopoietic precursor cells is the hallmark of aplastic anemia, but many features of this disease are shared by two related disorders, paroxysmal nocturnal hemoglobinuria (PNH) and myelodysplastic syndrome (MDS). While the clinical associations between hematological malignancy and autoimmunity have been described many decades ago, only in the last several years have the common pathogenetic mechanisms been elucidated. We summarize the recent progress made in understanding how hematological malignancy gives rise to autoimmunity directed against blood cells and vice versa, and illustrate parallels in the etiology of malignant and autoimmune hematological disorders. Specifically, recent progress in the recognition of the association of lymphoproliferative disorders and autoimmunity against mature blood cells, and common pathogenetic background of aplastic anemia, paroxysmal nocturnal hemoglobinuria, and myelodysplastic syndrome are discussed.

Allogeneic stem cell transplantation for aplastic anemia

Aplastic anemia encompasses a heterogeneous group of diseases with distinct pathophysiologies and a common clinical endpoint of marrow failure. Patients with severe aplastic anemia can be treated with immunosuppressive therapy (IST) or hematopoietic stem cell transplantation (HSCT). Over the last 30 years, advances in both treatment modalities have significantly improved the prognosis for this disease; yet this evolution complicates the central therapeutic question in aplastic anemia: which patients should receive IST and which ones should receive HSCT as front-line therapy? In this review, we describe the major improvements that have occurred in transplantation for aplastic anemia in the last 3 decades. We then outline a framework for deciding which patients should be considered for upfront transplantation.

Distinct EBV and CMV reactivation patterns following antibody-based immunosuppressive regimens in patients with severe aplastic anemia

The natural history of EBV and CMV reactivation and the potential for serious complications following antibody-based immunosuppressive treatment for bone marrow failure syndromes in the absence of transplantation is not known. We monitored blood for EBV and CMV reactivation by polymerase chain reaction (PCR) weekly in 78 consecutive patients (total of 99 immunosuppressive courses) with aplastic anemia. Four regimens were studied: (1) HC, horse ATG/cyclosporine; (2) HCS, horse ATG/CsA/sirolimus; (3) RC, rabbit ATG/CsA; and (4) CP, alemtuzumab. There were no cases of EBV or CMV disease, but EBV reactivation occurred in 82 (87%) of 94 and CMV reactivation in 19 (33%) of 57 seropositive patients after starting immunosuppression. The median peak EBV copies were higher in the RC group when compared with HC, HCS, and alemtuzumab (P < .001). The median duration of PCR positivity for EBV was higher in the RC group compared with HC, HCS, and alemtuzumab (P = .001). Subclinical reactivation of both EBV and CMV is common and nearly always self-limited in patients with bone marrow failure receiving immunosuppression; different regimens are associated with different intensity of immunosuppression as measured by viral load and lymphocyte count; and viral reactivation patterns differ according to immunosuppressive regimens.

Long-term outcome in acquired aplastic anemia treated with an intensified dose schedule of horse antilymphocyte globulin in combination with androgens

Aplastic anemia (AA) is a rare hematopoietic stem cell disease, which can be treated with horse antilymphocyte globulin (ALG) for patients not eligible for bone marrow transplantation. ALG gives about 60% overall survival rate (OS) after 5 years, a 30% of persistent complete remission and a 20% early death rate related to failure. ALG has been incriminated in the emergence of 10 to 20% therapy-related AML/MDS (t-AML/MDS) with the usual doses. Questions remain whether higher doses of ALG could improve the response and OS rates and whether the combination with androgens is able to protect patients from t-AML/MDS. We have carried out a single institutional retrospective study of 87 AA treated with higher doses of ALG, twice the usual posology (140 mg/kg instead of 75 mg/kg), combined to androgens. The overall response rate was 77% and the OS rate at 5 years was 78%. Androgens in combination with ALG improved response and OS rates. At diagnosis, 6% of AA had an abnormal karyotype using conventional cytogenetic not related to any time-to-event. Two patients displayed a cytogenetic conversion related to the occurrence of secondary malignancies. The incidence of t-AML/MDS was 2.3% with an estimated 10-year cumulative incidence of 3.1. Our results show that higher doses of ALG combined to androgens are feasible and give results close to those recently describe with the immunosuppressive treatments including ALG associated to cyclosporine, with a low SMD/AML incidence rate.

Current concepts in the pathophysiology and treatment of aplastic anemia

Aplastic anemia, an unusual hematologic disease, is the paradigm of the human bone marrow failure syndromes. Almost universally fatal just a few decades ago, aplastic anemia can now be cured or ameliorated by stem-cell transplantation or immunosuppressive drug therapy. The pathophysiology is immune mediated in most cases, with activated type 1 cytotoxic T cells implicated. The molecular basis of the aberrant immune response and deficiencies in hematopoietic cells is now being defined genetically; examples are telomere repair gene mutations in the target cells and dysregulated T-cell activation pathways. Immunosuppression with antithymocyte globulins and cyclosporine is effective at restoring blood-cell production in the majority of patients, but relapse and especially evolution of clonal hematologic diseases remain problematic. Allogeneic stem-cell transplant from histocompatible sibling donors is curative in the great majority of young patients with severe aplastic anemia; the major challenges are extending the benefits of transplantation to patients who are older or who lack family donors. Recent results with alternative sources of stem cells and a variety of conditioning regimens to achieve their engraftment have been promising, with survival in small pediatric case series rivaling conventional transplantation results.

Diagnosis and treatment of children with aplastic anemia

BACKGROUND

Long-term survival rates among children diagnosed with severe aplastic anemia (SAA) are excellent due to the success of human leukocyte antigen (HLA)-identical related hematopoietic stem cell transplantation (HSCT), concurrent advances in immunosuppressive treatment (IST), and improved supportive care. The challenge in making treatment recommendations for children with SAA, therefore, is to balance the apparent chronicity and morbidity following IST, with the potential up-front toxicity and complications of HSCT.

METHODS

This review provides an update on the diagnosis and a risk-based treatment algorithm for children with acquired SAA. Recent experience using alternative donor HSCT and efforts to extend HSCT eligibility through advances in donor matching, de-escalation of conditioning regimens, and potential marrow graft engineering are highlighted. We discuss IST response rates, risks of relapse, and complications including clonal evolution.

CONCLUSIONS

While good treatment options exist for a majority of children diagnosed with SAA, novel non-transplantation treatments for unresponsive and relapsed patients without suitable transplant donors are needed. Further improvements in outcome will ultimately require a more complete understanding of the pathophysiology of aplastic anemia (AA).

Management of acquired aplastic anaemia

Outcome of patients with aplastic anaemia (AA), whether treated with allogeneic BMT or immunosuppressive therapy has steadily increased over the last three decades. However, there is a difference in quality of outcome between these two therapeutic modalities. There is no plateau for survival after ATG as patients are at later risk of transformation to myelodysplasia (MDS) or acute myeloid leukaemia (AML), paroxysmal nocturnal haemoglobinuria and relapse of their aplasia. In contrast, AA patients are not at risk of these later complications if they have undergone successful bone marrow transplantation. Long term survival after HLA identical sibling BMT is 80-90%, but GVHD and graft rejection remain to be addressed. The results of unrelated donor BMT for AA have shown considerable improvement over the last five years. Difficulties remain for those patients who fail immunosuppressive therapy and in whom BMT is not possible, since alternative immunosuppressive agents have so far proven to be somewhat disappointing.

Natural history of moderate aplastic anemia in children

BACKGROUND

Moderate aplastic anemia (MAA) in children is a rare, idiopathic condition of bone marrow insufficiency that can resolve spontaneously, persist for months or years, or progress to severe aplastic anemia (SAA). We evaluated the rate of progression to SAA.

METHODS

We reviewed the records of 136 children referred for evaluation of bone marrow failure from 1978 to 2002 at St. Jude Children's Research Hospital. MAA was defined by a hypocellular bone marrow (<50%) and 2 or 3 cytopenias (absolute neutrophil count <1,500/mm(3), absolute reticulocyte count <40,000/mm(3), platelet count <100,000/mm(3)) lasting at least 6 weeks.

RESULTS

Twenty-four patients met the criteria for MAA. At a median follow-up of 66 months (range, 10-293), 16 patients (67%) progressed to SAA, 5 (21%) had persistent MAA, and 3 (12%) had complete resolution of MAA. No risk factors for progression could be identified.

CONCLUSIONS

When childhood MAA is treated with supportive care alone, 2/3 of patients progress to SAA.