Gregory Wallace

Diagnostic and risk criteria for HSCT-associated thrombotic microangiopathy: a study in children and young adults

Transplant-associated thrombotic microangiopathy (TMA) leads to generalized endothelial dysfunction that can progress to multiorgan injury, and severe cases are associated with poor outcomes after hematopoietic stem cell transplantation (HSCT). Identifying patients at highest risk for severe disease is challenging. We prospectively evaluated 100 consecutive HSCT recipients to determine the incidence of moderate and severe TMA and factors associated with poor overall outcomes. Thirty-nine subjects (39%) met previously published criteria for TMA. Subjects with TMA had a significantly higher nonrelapse mortality (43.6% vs 7.8%, P < .0001) at 1 year post-HSCT compared with those without TMA. Elevated lactate dehydrogenase, proteinuria on routine urinalysis, and hypertension were the earliest markers of TMA. Proteinuria (>30 mg/dL) and evidence of terminal complement activation (elevated sC5b-9) in the blood at the time of TMA diagnosis were associated with very poor survival (<20% at 1 year), whereas all TMA subjects without proteinuria and a normal sC5b-9 serum concentration survived (P < .01). Based on these prospective observations, we conclude that severe TMA occurred in 18% of HSCT recipients in our cohort and propose an algorithm to identify the highest-risk patients who might benefit from prompt clinical interventions.

New approaches in the diagnosis, pathophysiology, and treatment of pediatric hematopoietic stem cell transplantation-associated thrombotic microangiopathy

Hematopoietic stem cell transplantation (HSCT)-associated thrombotic microangiopathy (TA-TMA) is an understudied complication of HSCT that significantly affects transplant-related morbidity and mortality. Over the past several decades, the cause of TA-TMA has remained unknown, limiting treatment options to non-specific therapies adapted from other diseases. Recent prospective studies dedicated to the study of TA-TMA have provided new insights into the pathogenesis of, and genetic susceptibility to TA-TMA, raising awareness of this important transplant complication and allowing for the identification of potentially novel therapeutic targets. Specifically, many patients with TA-TMA develop multi-organ tissue injury through endothelial damage mediated by the activation of the complement pathway, leading to rational therapeutic strategies including complement blockade. This new knowledge has the potential to favorably influence clinical practice and change the standard of care for how patients with TA-TMA are managed. In this review, we summarize novel approaches to the recognition and management of TA-TMA, using case examples to illustrate key clinical points that hopefully lead to improved short and long-term outcomes for these complex HSCT patients, who remain at significant risk for treatment-related morbidity and mortality.

Histologic Features of Intestinal Thrombotic Microangiopathy in Pediatric and Young Adult Patients after Hematopoietic Stem Cell Transplantation

High-risk transplantation-associated thrombotic microangiopathy (TMA) can present with multisystem involvement and is associated with a poor outcome after hematopoietic stem cell transplantation (HSCT), with < 20% 1-year survival. TMA may involve the intestinal vasculature and can present with bleeding and ischemic colitis. There are no established pathologic criteria for the diagnosis of intestinal TMA (iTMA). The goal of our study was to identify histologic features of iTMA and describe associated clinical features. We evaluated endoscopic samples from 50 consecutive HSCT patients for 8 histopathologic signs of iTMA and compared findings in 3 clinical groups based on the presence or absence of systemic high-risk TMA (hrTMA) and the presence or absence of clinically staged intestinal graft-versus-host disease (iGVHD): TMA/iGVHD, no TMA/iGVHD, and no TMA/no iGVHD. Thirty percent of the study subjects had a clinical diagnosis of systemic hrTMA. On histology, loss of glands, intraluminal schistocytes, intraluminal fibrin, intraluminal microthrombi, endothelial cell separation, and total denudation of mucosa were significantly more common in the hrTMA group (P < .05). Intravascular thrombi were seen exclusively in patients with hrTMA. Mucosal hemorrhages and endothelial cell swelling were more common in hrTMA patients but this difference did not reach statistical significance. Patients with hrTMA were more likely to experience significant abdominal pain and gastrointestinal bleeding requiring multiple blood transfusions (P < .05). Our study shows that HSCT patients with systemic hrTMA can have significant bowel vascular injury that can be identified using defined histologic criteria. Recognition of these histologic signs in post-transplantation patients with significant gastrointestinal symptoms may guide clinical decisions.

Healthcare Burden, Risk Factors, and Outcomes of Mucosal Barrier Injury Laboratory-Confirmed Bloodstream Infections after Stem Cell Transplantation

Mucosal barrier injury laboratory-confirmed bloodstream infections (MBI-LCBIs) lead to significant morbidity, mortality, and healthcare resource utilization in hematopoietic stem cell transplant (HSCT) patients. Determination of the healthcare burden of MBI-LCBIs and identification of patients at risk of MBI-LCBIs will allow researchers to identify strategies to reduce MBI-LCBI rates. The objective of our study was to describe the incidence, risk factors, timing, and outcomes of MBI-LCBIs in hematopoietic stem cell transplant patients. We performed a retrospective analysis of 374 patients who underwent HSCT at a large free-standing academic childrens hospital to determine the incidence, risk factors, and outcomes of patients that developed a bloodstream infection (BSI) including MBI-LCBI, central line-associated BSI (CLABSI), or secondary BSI in the first year after HSCT. Outcome measures included nonrelapse mortality (NRM), central venous catheter removal within 7 days of positive culture, shock, admission to the pediatric intensive care unit (PICU) within 48 hours of positive culture, and death within 10 days of positive culture. One hundred seventy BSIs were diagnosed in 100 patients (27%): 80 (47%) MBI-LCBIs, 68 (40%) CLABSIs, and 22 (13%) secondary infections. MBI-LCBIs were diagnosed at a significantly higher rate in allogeneic HSCT patients (18% versus 7%, P = .007). Reduced-intensity conditioning (OR, 1.96; P = .015) and transplant-associated thrombotic microangiopathy (OR, 2.94; P = .0004) were associated with MBI-LCBI. Nearly 50% of all patients with a BSI developed septic shock, 10% died within 10 days of positive culture, and nearly 25% were transferred to the PICU. One-year NRM was significantly increased in patients with 1 (34%) and more than 1 (56%) BSIs in the first year post-HSCT compared with those who did not develop BSIs (14%) (P ≤ .0001). There was increased 1-year NRM in patients with at least 1 MBI-LCBI (OR, 1.94; P = .018) and at least 1 secondary BSI (OR, 2.87; P = .0023) but not CLABSIs (OR, 1.17; P = .68). Our data demonstrate that MBI-LCBIs lead to substantial use of healthcare resources and are associated with significant morbidity and mortality. Reduction in frequency of MBI-LCBI should be a major public health and scientific priority.

Vitamin D Deficiency and Survival in Children after Hematopoietic Stem Cell Transplant.

Vitamin D has endocrine function as a key regulator of calcium absorption and bone homeostasis and also has intracrine function as an immunomodulator. Vitamin D deficiency before hematopoietic stem cell transplantation (HSCT) has been variably associated with higher risks of graft-versus-host disease (GVHD) and mortality. Children are at particular risk of growth impairment and bony abnormalities in the face of prolonged deficiency. There are few longitudinal studies of vitamin D deficient children receiving HSCT, and the prevalence and consequences of vitamin D deficiency 100 days after transplant has been poorly studied. Serum samples from 134 consecutive HSCT patients prospectively enrolled into an HSCT sample repository were tested for 25-hydroxy (25 OH) vitamin D levels before starting HSCT (baseline) and at 100 days after transplantation. Ninety-four of 134 patients (70%) had a vitamin D level < 30 ng/mL before HSCT, despite supplemental therapy in 16% of subjects. Post-transplant samples were available in 129 patients who survived to day 100 post-transplant. Vitamin D deficiency persisted in 66 of 87 patients (76%) who were already deficient before HSCT. Moreover, 24 patients with normal vitamin D levels before HSCT were vitamin D deficient by day 100. Overall, 68% of patients were vitamin D deficient (<30 ng/mL) at day 100, and one third of these cases had severe vitamin D deficiency (<20 ng/mL). Low vitamin D levels before HSCT were not associated with subsequent acute or chronic GVHD, contrary to some prior reports. However, severe vitamin D deficiency (<20 ng/mL) at 100 days post-HSCT was associated with decreased overall survival after transplantation (P = .044, 1-year rate of overall survival: 70% versus 84.1%). We conclude that all pediatric transplant recipients should be screened for vitamin D deficiency before HSCT and at day 100 post-transplant and that aggressive supplementation is needed to maintain sufficient levels.

Pulmonary hypertension associated with bronchiolitis obliterans after hematopoietic stem cell transplantation.

Pulmonary hypertension (PH) is a rare and potentially fatal complication of hematopoietic stem cell transplantation (HSCT). PH arises from increased pulmonary vascular resistance leading to increased right ventricular pressure (RVP), right heart failure and death.1 PH is often difficult to diagnose as symptoms can be nonspecific, including shortness of breath, fatigue, weakness and hypoxemia, and may also result in death if left untreated.2

Poor growth, thyroid dysfunction and vitamin D deficiency remain prevalent despite reduced intensity chemotherapy for hematopoietic stem cell transplantation in children and young adults

Myeloablative conditioning regimens for hematopoietic stem cell transplant (HSCT) are known to affect endocrine function, but little is known regarding reduced intensity conditioning (RIC) regimens. We retrospectively reviewed 114 children and young adults after single RIC HSCT. The analysis was grouped by age (<2 and ⩾2 years) and diagnosis (hemophagocytic lymphohistiocystosis/X-linked lymphoproliferative syndrome (HLH/XLP), other immune disorders, metabolic/genetic disorders). All groups displayed short stature by mean height-adjusted Z-score (HAZ) before (−1.29) and after HSCT (HAZ −1.38, P=0.47). After HSCT, younger children with HLH/XLP grew better (HAZ −3.41 vs −1.65, P=0.006), whereas older subjects had decline in growth (HAZ −0.8 vs −1.01, P=0.06). Those with steroid therapy beyond standard GVHD prophylaxis were shorter than those without (P 0.04). After HSCT, older subjects with HLH/XLP became thinner with a mean body mass index (BMI) Z-score of 1.20 vs 0.64, P=0.02, and similar to metabolic/genetic disorders (BMI-Z= 0.59 vs −0.99, P<0.001). BMI increased among younger children in these same groups. Thyroid function was abnormal in 24% (18/76). 25-OH vitamin D levels were insufficient in 73% (49/65), with low bone mineral density in 8 of 19 evaluable subjects. Despite RIC, children and young adults still have significant late endocrine effects. Further research is required to compare post-transplant endocrine effects after RIC to those after standard chemotherapy protocols.

Lower levels of vitamin A are associated with increased gastrointestinal graft-versus-host disease in children

Vitamin A promotes development of mucosal tolerance and enhances differentiation of regulatory T cells. Vitamin A deficiency impairs epithelial integrity, increasing intestinal permeability. We hypothesized that higher vitamin A levels would reduce the risk of graft-versus-host disease (GVHD) through reduced gastrointestinal (GI) permeability, reduced mucosal injury, and reduced lymphocyte homing to the gut. We tested this hypothesis in a cohort study of 114 consecutive patients undergoing allogeneic stem cell transplant. Free vitamin A levels were measured in plasma at day 30 posttransplant. GI GVHD was increased in patients with vitamin A levels below the median (38% vs 12.4% at 100 days, P = .0008), as was treatment-related mortality (17.7% vs 7.4% at 1 year, P = .03). Bloodstream infections were increased in patients with vitamin A levels below the median (24% vs 8% at 1 year, P = .03), supporting our hypothesis of increased intestinal permeability. The GI mucosal intestinal fatty acid-binding protein was decreased after transplant, confirming mucosal injury, but was not correlated with vitamin A levels, indicating that vitamin A did not protect against mucosal injury. Expression of the gut homing receptor CCR9 on T-effector memory cells 30 days after transplant was increased in children with vitamin A levels below the median (r = -0.34, P = .03). Taken together, these data support our hypothesis that low levels of vitamin A actively promote GI GVHD and are not simply a marker of poor nutritional status or a sicker patient. Vitamin A supplementation might improve transplant outcomes.

RSV infection without ribavirin treatment in pediatric hematopoietic stem cell transplantation

RSV infection without ribavirin treatment in pediatric hematopoietic stem cell transplantation

A Complete Histologic Approach to Gastrointestinal Biopsy From Hematopoietic Stem Cell Transplant Patients With Evidence of Transplant-Associated Gastrointestinal Thrombotic Microangiopathy

CONTEXT - Transplant-associated thrombotic microangiopathy is a serious complication of hematopoietic stem cell transplant that may progress to multi-organ dysfunction. Transplant-associated thrombotic microangiopathy may involve the intestinal vasculature (intestinal transplant-associated thrombotic microangiopathy [iTMA]), causing patients to experience debilitating symptoms of ischemic colitis, including disproportionately severe abdominal pain and gastrointestinal bleeding, requiring heavy narcotic use and frequent transfusion support. Pathophysiology remains poorly investigated but may include endothelial damage mediated by inflammatory markers and the complement system. Endoscopy of hematopoietic stem cell transplant patients often produces biopsy samples, in which mucosal lamina propria capillaries are sufficient for an evaluation of iTMA features. OBJECTIVE - To provide a detailed review of histologic features of iTMA. DATA SOURCES - We conducted a systematic review of studies assessing histologic features of iTMA. Studies were identified by PubMed search and included a cohort study performed by our group. CONCLUSIONS - The histologic hallmark of iTMA is endothelial cell injury that leads to hemorrhage and thrombosis of the capillaries. Histologic features include endothelial cell swelling, endothelial cell separation, perivascular mucosal hemorrhage, intraluminal schistocytes, intraluminal fibrin, intraluminal microthrombi, loss of glands, and total denudation of mucosa. Identification of features consistent with iTMA has immediate implications for clinical management that could potentially improve outcome and survival.