Thrombotic thrombocytopenic purpura-hemolytic uremic syndrome following allogeneic HPC transplantation: a diagnostic dilemma

Thrombotic microangiopathies: an update

Thrombotic microangiopathies (TMA) are microvascular occlusive disorders characterized by hemolytic anemia caused by fragmentation of erythrocytes and thrombocytopenia due to increased platelet aggregation and thrombus formation, eventually leading to disturbed microcirculation with reduced organ perfusion. Although several disease states may manifest as TMA, the two most relevant conditions associated with TMA are thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), characterized by prominent brain or renal lesions, respectively. However, occasionally the clinical distinction between these two conditions can be difficult. In this review, we focus on the epidemiologic and diagnostic criteria as well as on the most recent insights into the pathophysiology and treatment of these two conditions.

Acute renal failure after allogeneic myeloablative stem cell transplantation: retrospective analysis of incidence, risk factors and survival

Acute renal failure (ARF) is an important complication after stem cell transplantation (SCT). We retrospectively analysed ARF in 363 recipients of allogeneic myeloablative SCT to identify incidence, risk factors, associated post-transplantation complications and mortality of ARF. ARF was graded as grade 0 (no ARF) to grade 3 (need for dialysis) according to creatinine, estimated glomerular filtration rate and need for dialysis. The incidence of severe renal failure (grades 2 and 3 combined) was 49.6% (180 of 363 patients). Hypertension present at SCT was identified as a risk factor for ARF (P=0.003). Despite this, survival of these patients was not different compared to patients without hypertension. Admission to the intensive care unit (ICU) was a post-transplantation complication significantly associated with ARF (P<0.001). Survival rate was highest in patients with ARF grade 0-1 and lowest in patients with grade 3 (P<0.001). However, after correction for complications associated with high mortality (admission to the ICU, thrombotic thrombocytopenic purpura, sinusoidal occlusion syndrome (SOS) and acute graft-versus-host disease) the significant difference in survival disappeared, showing that ARF without co-morbid conditions has a good prognosis, and ARF with co-morbid conditions has a poor prognosis. This poor prognosis is due to the presence of co-morbid conditions rather than development of ARF itself.

Post-appendectomy thrombotic thrombocytopenic purpura: a case report and review of the literature

Thrombotic thrombocytopenic purpura (TTP) is a syndrome characterized by microangiopathic hemolytic anemia and thrombocytopenia with varying degrees of renal dysfunction, neurologic signs and symptoms, and fever. Evidence has supported that a large proportion of cases of acquired TTP are due to the accumulation of ultralarge von Willebrand factor (vWF) multimers due to an acquired deficiency in the vWF cleaving protease, ADAMTS-13. TTP is rare in the post-surgical setting but is best described after cardiothoracic and vascular surgeries. We present a case of postoperative TTP first presenting with microangiopathic hemolytic anemia and thrombocytopenia 9 days after emergent appendectomy for a ruptured appendix. ADAMTS-13 and factor H levels returned normal and an ADAMTS-13 inhibitor was not identified. To our knowledge, this is the first case report of postoperative TTP after an appendectomy and the first report with correlative ADAMTS-13 data. Plasma exchange with fresh frozen plasma followed by cryopoor plasma, along with steroids resulted in eventual remission of TTP in our patient. Early postoperative diagnosis and aggressive management with consideration of initiation of plasma exchange is imperative to decrease the morbidity and morality associated with TTP.

Thrombotic microangiopathy following allogeneic hematopoietic stem cell transplantation

PURPOSE OF REVIEW

The aim of this article is to assess the current understanding and uncertainties about the evaluation and management of thrombotic microangiopathy that occurs following allogeneic hematopoietic stem cell transplantation.

RECENT FINDINGS

Current data may not be sufficient to establish posttransplantation thrombotic microangiopathy as a discrete clinical or pathologic entity, distinct from other well recognized transplant-related complications. Analysis of case series of posttransplantation thrombotic microangiopathy illustrates uncertainties regarding incidence, risk factors, diagnosis, treatment, and survival. These studies have suggested the lack of efficacy of plasma exchange treatment and have identified other transplant-related complications, such as acute graft-versus-host disease and opportunistic infections, as the predominant causes of death in patients who had been diagnosed with posttransplantation thrombotic microangiopathy. Recently consensus diagnostic criteria were proposed by two independent groups to provide more uniform identification of patients with posttransplantation thrombotic microangiopathy; these criteria may result in a clearer definition of this syndrome.

SUMMARY

Posttransplantation thrombotic microangiopathy remains a diagnostic and therapeutic challenge. Further studies are required to determine if it is a specific entity and to define its relation to other transplant-related complications.

Transplant-associated microangiopathy in patients receiving tacrolimus following allogeneic stem cell transplantation: risk factors and response to treatment

Transplant-associated microangiopathy (TAM) is a life-threatening complication after allogeneic HSCT, particularly with the use of calcineurin inhibitors as post-transplantation immunosuppressive therapy. We report our experience with TAM after HSCT with tacrolimus-based GVHD prophylaxis in a single-center study. Sixty-six of 1219 transplant recipients developed TAM with a cumulative incidence of 5.9%. Risk factors for TAM were female gender, lymphoid malignancy, receipt of a matched unrelated donor, and grade II-IV aGVHD. Most patients had infection and/or active GVHD at the diagnosis of TAM (82%). In the absence of renal dysfunction or encephalopathy, tacrolimus was generally continued, maintaining blood levels within the lower therapeutic range. Sixty-three patients were treated with plasma exchange. The cumulative incidence of response of TAM was 60%. Only 1 patient had a response of TAM without resolution of concomitant infections or GVHD. Six-month survivals were 0% and 50% for TAM nonresponders and responders, respectively. In conclusion, TAM is a common, life-threatening complication of allogeneic hematopoietic transplantation using tacrolimus prophylaxis. Control of TAM generally requires response of associated infections and GVHD. TMA response may occur despite continuation of tacrolimus treatment.

Circulating Endothelial Cells as a Prognostic Marker in Thrombotic Microangiopathy

BACKGROUND

Circulating endothelial cells (CECs) are a reliable marker of disease activity in a variety of vascular disorders. Damage to microvascular endothelial cells is a hallmark of thrombotic microangiopathy (TMA). The aim of this study is to identify and count CECs during the course of TMA and evaluate whether cell numbers may serve as a prognostic marker in patients undergoing plasma exchange.

METHODS

Fifteen patients (8 women, 7 men) aged 31 to 66 years with TMA of different causes were studied before and after 4 sessions of plasma exchange. CECs were isolated by using anti-CD146-driven immunomagnetic isolation and counted after staining with Ulex Europaeus lectin-1.

RESULTS

Numbers of CECs were markedly elevated in all patients before treatment (64 to 672 CEC/mL; mean, 320 +/- 205 CEC/mL) compared with healthy controls (0 to 16 CEC/mL; mean, 6.4 +/- 4.2 CEC/mL; P < 0.001). Patients with a favorable outcome had significantly greater initial CEC levels (mean, 426 +/- 175 CEC/mL; P < 0.001), and cell numbers decreased significantly after 4 treatments of plasma exchange (mean, 101 +/- 53 CEC/mL; P = 0.001). Patients with disease unresponsive to plasma exchange presented with lower initial CEC levels (mean, 108 +/- 36 CEC/mL), and numbers failed to decrease after plasma exchange (mean, 114 +/- 57 CEC/mL; P = 0.827).

CONCLUSION

Markedly elevated numbers of CECs reflect severe and widespread endothelial damage in patients with TMA. Cell numbers at presentation and their degree of decrease after 4 sessions of plasma exchange could provide important prognostic clues.

Risk Factors and Severe Outcome in Thrombotic Microangiopathy After Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND

Thrombotic microangiopathy (TMA) has been described as severe complication after hematopoietic stem cell transplantation (HSCT). The principal aim of this study was to focus the incidence and the outcome of TMA in the era of more complex HSCTs.

METHODS

We analyzed the role of some predicting factors for the incidence and the outcome of TMA after HSCT. We enrolled 539 consecutive patients (307 males, median age 31 years) undergoing HSCT from match or mismatch human leukocyte antigen family donor (314) or match/mismatch unrelated (195) and haploidentical donor (30) for malignant or nonmalignant diseases. TMA diagnosis was performed by homogeneous clinical and laboratory criteria.

RESULTS

Sixty-four of 539 patients presented TMA (11,87%) and the five-year cumulative incidence of TMA was 14% (HR=0.13). Fifty nine of 64 patients were affected by malignant and 5/64 by non-malignant diseases. On multivariate analysis, TMA occurrence was influenced by graft versus host disease >grade II (P=0.0001), donor type (P=0.029), gender (P=0.0233), total body irradiation based conditioning regimen (P=0.0041). Three factors for TMA outcome proved to be statistically significant by multivariate analysis: age (P=0.009), donor type (P=0.0187) and TMA index (P=0.029). The TMA mortality rate was 50%. The outcome was influenced by defibrotide (P=0.02 in univariate analysis).

CONCLUSIONS

The study underlines the possibility of finding out which patients are more prone to developing post-HSCT TMA, and identifies which risk factors are more frequently associated with a dismal outcome after TMA.

Prospective study on the behaviour of the metalloprotease ADAMTS13 and of von Willebrand factor after bone marrow transplantation

Thrombotic microangiopathies (TMAs) are rare but serious complications of bone marrow transplantation (BMT). Clinical manifestations are similar to those of thrombotic thrombocytopenic purpura (TTP), but prognosis is generally poorer despite plasma exchange. The enzymatic activity of the plasma metalloprotease ADAMTS13, which cleaves ultralarge thrombogenic multimers of von Willebrand factor (VWF) derived from activated endothelial cells, is very low or undetectable in patients with classic TTP, and protease deficiency is thought to play a mechanistic role in the formation of platelet thrombi in the microcirculation. This is the first prospective study to evaluate the incidence of TMA in 46 consecutively recruited patients undergoing autologous or allogeneic BMT and explore in parallel the behaviour of ADAMTS13, VWF antigen and VWF multimer size. The incidence of post-BMT TMA was 6% (three of 46); all cases occurred after allogeneic BMT. Compared with baseline values plasma ADAMTS13 activity was significantly reduced in patients undergoing BMT, particularly after the conditioning regimen (mean values: 50 +/- 22 vs. 77 +/- 32%; P < 0.0001). In the three patients who developed TMA, ADAMTS13 decreased after conditioning, but was very low in one case only (8%). VWF antigen levels progressively increased after the conditioning regimen (228 +/- 75 vs. 178 +/- 76% at baseline, P = 0.002). The mean proportion of high-molecular weight VWF multimers did not change in the various stages of BMT, even though ultralarge multimers were transiently found in same cases with and without TMA. Hence, the measurements evaluated in this study are not clinically useful to predict the occurrence of post-BMT TMA.

Risk factor analysis for thrombotic microangiopathy after reduced-intensity or myeloablative allogeneic hematopoietic stem cell transplantation

Thrombotic microangiopathy (TMA) impairs long-term survival after allogeneic hematopoietic stem cell transplantation (HSCT). As the allogeneic HSCT procedure has developed, addressing risk factors for TMA has become more complicated. The aim of this study was to investigate the impact of transplant-associated factors on TMA incidence in patients who have undergone HSCT in various settings. One hundred twenty-three consecutive allogeneic HSCT patients with hematologic diseases receiving myeloablative and reduced-intensity conditioning were evaluated retrospectively. Of 123 patients, 22 (17.9%) developed TMA after HSCT. Multivariate analysis showed the significance of GVHD grade II-IV, and the use of FK506 and the use of high-dose busulfan (Bu) (16 mg/kg) persisted. The hazard ratios of the use of FK506, the use of high-dose Bu (16 mg/kg), and GVHD grade II-IV for TMA were 8.7 (95% CI 2.0-37), 5.7 (95% CI 1.5-21), and 3.4 (95% CI 1.3-9.1), respectively. In the present study, reduced-intensity conditioning did not have an advantage over myeloablative conditioning in decreasing the incidence of TMA after HSCT. Our results also showed that high-dose Bu (16 mg/kg) for the conditioning and FK506 for the prophylaxis of GVHD might contribute more significantly to TMA onset after HSCT than other agents.

Thrombotic Microangiopathy With Acquired Deficiency in ADAMTS 13 Activity in Lung Transplant Recipients

BACKGROUND

Thrombotic microangiopathy may develop after solid organ transplantation, but it is usually not associated with severe deficiency in von Willebrand factor-cleaving metalloprotease (ADAMTS 13) activity.

METHODS

We present the cases of two lung transplant recipients who experienced a thrombotic microangiopathy associated with an acquired severe (<5%) deficiency in ADAMTS 13 activity.

RESULTS

A major feature of both cases was the occurrence of a diffuse alveolar hemorrhage.

CONCLUSION

Our two cases of lung transplant patients, with thrombotic microangiopathy related to an acquired ADAMTS 13 deficiency recipients, confirm that this mechanism may also be involved in the pathogenesis of thrombotic microangiopathy developing after solid organ transplantation. Therefore, we consider that ADAMTS 13 activity should be assessed on a systematic basis in this setting.

A classification of hemolytic uremic syndrome and thrombotic thrombocytopenic purpura and related disorders

The diagnostic terms hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are based on historical and overlapping clinical descriptions. Advances in understanding some of the causes of the syndrome now permit many patients to be classified according to etiology. The increased precision of a diagnosis based on causation is important for considering logical approaches to treatment and prognosis. It is also essential for research. We propose a classification that accommodates both a current understanding of causation (level 1) and clinical association in cases for whom cause of disease is unclear (level 2). We tested the classification in a pediatric disease registry of HUS. The revised classification is a stimulus to comprehensive investigation of all cases of HUS and TTP and is expected to increase the proportion of cases in whom a level 1 etiological diagnosis is confirmed.

Sirolimus and thrombotic microangiopathy after allogeneic hematopoietic stem cell transplantation

Thrombotic microangiopathy (TMA) may occur after allogeneic hematopoietic stem cell transplantation (HSCT) and is related in part to calcineurin inhibitor toxicity. We observed a higher-than-expected rate of TMA when calcineurin inhibitors were combined with sirolimus. To determine the incidence of and risk factors for TMA after HSCT, we performed a retrospective cohort analysis of myeloablative allogeneic HSCT recipients between 1997 and 2003. TMA diagnosis required the simultaneous occurrence of (1) creatinine increase >2 mg/dL or >50% above baseline, (2) schistocytosis, (3) increased lactate dehydrogenase, and (4) no evidence of disseminated intravascular coagulopathy. A total of 111 sirolimus-exposed subjects were compared with 216 nonexposed subjects after HSCT. TMA occurred in 10.8% of the sirolimus group and 4.2% in the nonsirolimus group (odds ratio, 2.79; P=.03). Sirolimus exposure was associated with TMA earlier than in nonsirolimus patients (25 versus 58 days; P=.04). Only the use of sirolimus (exact odds ratio, 3.49; P=.02) and grade II to IV acute graft-versus-host disease (exact odds ratio, 6.60; P=.0002) were associated with TMA in regression analyses. Treatment of TMA varied among affected individuals. Renal recovery was complete in 92% of sirolimus-treated patients. Overall survival after TMA diagnosis was better for sirolimus subjects than for nonsirolimus subjects (58.3% versus 11.1%; P=.02). Sirolimus seems to potentiate the effects of calcineurin inhibitors on TMA after HSCT. TMA associated with sirolimus seems reversible and has a favorable prognosis when compared with TMA associated with calcineurin inhibitors alone. A careful monitoring strategy for TMA should be used with a sirolimus-containing graft-versus-host disease prophylaxis regimen.

Blood and marrow transplant clinical trials network toxicity committee consensus summary: thrombotic microangiopathy after hematopoietic stem cell transplantation

The syndrome of microangiopathic hemolysis associated with renal failure, neurologic impairment, or both is a recognized complication of hematopoietic stem cell transplantation. This entity is often called hemolytic uremic syndrome (HUS) or thrombotic thrombocytopenic purpura (TTP), yet it is clear that the pathophysiology of transplant-associated HUS/TTP is different from that of classic HUS or TTP. Furthermore, the incidence of this syndrome varies from 0.5% to 76% in different transplant series, primarily because of the lack of a uniform definition. The toxicity committee of the Blood and Marrow Transplant Clinical Trials Network has reviewed the current literature on transplant-related HUS/TTP and recommends that it be henceforth renamed posttransplantation thrombotic microangiopathy (TMA). An operational definition for TMA based on the presence of microangiopathic hemolysis and renal and/or neurologic dysfunction is proposed. The primary intervention after diagnosis of TMA should be withdrawal of calcineurin inhibitors. Plasma exchange, although frequently used in this condition, has not been proven to be effective. In the absence of definitive trials, plasma exchange cannot be considered a standard of care for TMA. It is hoped that these positions will improve the identification and reporting of this devastating complication after hematopoietic stem cell transplantation and facilitate future clinical studies for its prevention and treatment.

Transplant-associated microangiopathy (TAM) in recipients of allogeneic hematopoietic stem cell transplants

We studied occurrence, risk factors and outcome of patients with transplant-associated microangiopathy (TAM) after allogeneic stem cell transplantation (HSCT). A total of 221 consecutive patients were transplanted between 1995 and 2002. TAM is defined as evidence of hemolysis and schistocytes in the first 100 days. Outcomes analyzed included TAM and overall survival. Of 221 patients, 68 had TAM. The cumulative incidence was 31 (25-38)% at 100 days. Patients with TAM had higher LDH, higher bilirubin, higher creatinine and more often neurologic symptoms. TAM was not associated with stem cell source, cyclosporine levels and was not more frequent in recent years. In multivariate analysis, risk factors for TAM included donor type, age, gender, ABO-incompatibility and acute graft-versus-host disease (aGvHD). In patients with TAM, 1-year survival was lower than in patients without TAM (27 +/- 18% for TAM with high schistocyte counts; 53 +/- 15% for TAM with low schistocyte counts; vs 78 +/- 7% in patients without TAM; P<0.0001). TAM was independently associated with mortality adjusting for donor type, age and aGvHD occurrence and severity. TAM is frequent after HSCT and is associated with mortality even after adjustment for aGvHD grade. Risk factors of TAM are similar to aGvHD. TAM may represent endothelial damage driven by donor-host interactions.

Usefulness of particle image analyzer for evaluation of fragmented red cells

Quantitative determination of fragmented red cells (FRCs) in peripheral blood is useful in various clinical fields. We have previously reported an automatic detection method using a hematology analyzer essentially based on detection of small red cells. We then tried to use another instrument, the FPIA 2100, to reflect the characteristic morphology of red cells. As the circularity obtained by FPIA 2100 correlated with the FRC%, this type of instrument might be helpful to establish better automatic detection methods.

Usefulness of Sequential Automated Analysis of Fragmented Red Blood Cells for the Differential Diagnosis of Thrombotic Thrombocytopenic Purpura-Hemolytic Uremic Syndrome following Allogeneic Hematopoietic Cell Transplantation

Differentiating thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) from other complications following allogeneic hematopoietic cell transplantation (HPCT) requires objective, reliable markers. To this purpose, we assessed the clinical usefulness of sequential quantified analysis of fragmented red blood cells (FRC) with the Sysmex XE-2100 automated hematology analyzer. The correlation between manual and automated counting was significant (r = 0.917; P < .0001). Of 25 cases, the peak FRC percentage (FRC%) exceeded 1.3% after allogeneic HPCT in 11 cases, and lactate dehydrogenase levels were elevated in 5 of these 11 cases. Two patients received diagnoses of TTP-HUS following allogeneic HPCT, and both had initial diagnoses of acute graft-versus-host disease. In both cases, the sharp increase in the FRC% to >3% simultaneously with clinical exacerbation was helpful for differentiating TTP-HUS following allogeneic HPCT from other complications. We conclude that FRC% data sequentially obtained by an automated count seem to be useful as an objective marker of TTP-HUS following allogeneic HPCT.

Sirolimus for GVHD prophylaxis in allogeneic stem cell transplantation

Sirolimus is a novel macrolide immunosuppressant widely used in solid organ transplantation. We have conducted three clinical trials using this compound as prophylaxis against GVHD after allogeneic stem cell transplantation. Our studies have demonstrated excellent GVHD control even when mismatched and unrelated donors were used. The morbidity and mortality associated with transplantation were reduced due to the omission or reduction in methotrexate dose. Furthermore, CMV reactivation and fungal infection rates were low. However, we have noted that sirolimus may be associated with increased rates of thrombotic microangiopathy after transplantation. Sirolimus has other uses, such as the treatment of established acute and chronic GVHD, and may be useful for treatment of post transplant lymphoproliferative disorder and perhaps as an antineoplastic agent against a wide variety of hematologic and solid neoplasms.

Thrombotic Microangiopathy after Allogeneic Blood and Marrow Transplantation Is Associated with Dose-Intensive Myeloablative Conditioning Regimens, Unrelated Donor, and Methylprednisolone T-Cell Depletion

BACKGROUND

Allogeneic blood and marrow transplantation (BMT)-associated thrombotic microangiopathy (TM) contributes to transplant-related morbidity and mortality. This report examines the incidence of and risk factors for allogeneic BMT-associated TM in two patient cohorts treated before and after changes in myeloablative conditioning regimen intensity (high vs. standard intensity).

METHODS

Cohort 1 includes 153 consecutive allogeneic BMT patients who underwent transplantation between April 1994 and October 1997 with an allogeneic BMT-associated TM crude incidence of 12%. Cohort 2 includes 75 consecutive allogeneic BMT patients who underwent transplantation from November 1997 to November 2000 with an allogeneic BMT-associated TM crude incidence of 1%.

RESULTS

In cohort 1, matched unrelated donor transplant and methylprednisolone (MP) T-cell depletion (TCD) of donor bone marrow were significantly associated with allogeneic BMT-associated TM by univariate analysis; therefore, a logistic model incorporating these effects was constructed to calculate the expected number of allogeneic BMT-associated TM cases in cohort 2. Seven cases would have been expected, but only one was observed (P = 0.003; bayesian predictive test). The multivariate analysis of both cohorts yielded MP-TCD (P<0.001), high-intensity myeloablative conditioning regimens used in cohort 1 (P = 0.02), and matched unrelated donor (P = 0.03) as significant predictors of time to allogeneic BMT-associated TM.

CONCLUSION

Avoidance of high-intensity conditioning regimens may decrease the incidence of allogeneic BMT-associated TM.

The Oklahoma Thrombotic Thrombocytopenic Purpura-Hemolytic Uremic Syndrome Registry: a program for patient care, education and research

The Oklahoma Thrombotic Thrombocytopenic Purpura-Hemolytic Uremic Syndrome (TTP-HUS) Registry was created by collaboration of the Oklahoma Blood Institute and the Colleges of Medicine and Public Health of the University of Oklahoma Health Sciences Center, combining their respective strengths of community service, patient care, education, and clinical research methodology. The organization of the Registry is based on the fundamental principles of patient-oriented research: 1) all consecutive patients are identified at a uniform time early in the course of their disease; 2) analysis of clinical data requires quantitative and reproducible definitions; 3) patient follow-up is complete; and 4) therefore the data are generalizable to community practice. A summary of 15 years experience with 301 consecutive patients is presented. Some of these results and interpretations are different from other case series. These differences emphasize the distinct perspective of the Registry that includes all patients in the community who have had a clinical diagnosis of TTP or HUS and for whom plasma-exchange treatment was requested. The Oklahoma TTP-HUS Registry provides educational and research opportunities, in addition to improved patient care, and serves as a model for productive collaboration of community blood centers and universities.