Anti-Glycoprotein Antibodies and Sequestration Pattern of Indium Labeled Platelets in Immune Thrombocytopenia

Anti-glycoprotein antibodies play an important role in the pathophysiology of immune thrombocytopenia (ITP). The sequestration pattern of platelets in spleen and liver can be studied with Indium-111 labeled autologous platelet scans. No studies have investigated the role of anti-GP antibodies in sequestration pattern in ITP patients. In this study we examined the association between antibodies and 1) platelet sequestration site and 2) clearance rate of platelets. All ITP patients receiving an Indium-111 labeled autologous platelet study between 2014 and 2018 were included. Antibodies were measured using the direct MAIPA method to determine the presence and titer of anti-GPIIb/IIIa, anti-GPIb/IX and anti-GPV antibodies. Multivariate regression models were used to study the association between anti-GP antibodies, sequestration site and clearance rate. Seventy-four patients were included, with a mean age of 36 years. Forty-seven percent of the patients showed a predominantly splenic sequestration pattern, 29% mixed and 25% a hepatic pattern. In 53% of the patients anti-GP antibodies were detected. Regression models showed a significant association between splenic sequestration and GPV autoantibodies.. Furthermore, in patients where antibodies were present the clearance rate was higher in patients with a splenic sequestration. Anti-GPV antibodies are associated with a splenic sequestration pattern in ITP patients. These associations provide insight in the possible pathophysiological mechanisms of ITP, which may lead to better detection and treatment of this partly idiopathic and prevalent disease.

A case of severe multi-system disease in a sickle cell SC patient caused by parvovirus B19 infection

Sickle Cell Disease (SCD) is an inherited hemoglobinopathy, which results in production of abnormal hemoglobin S. HbSC disease is a variant of SCD, which shares a similar clinical complication profile to HbSS disease, but often thought to be a milder condition. In patients with SCD, Hb S in deoxygenated state undergoes polymerization, leading to hemolysis, vaso-occlusive events, and eventually end-organ damage. Among other complications in patients with SCD is increased risk of complications caused by parvovirus B19. We present a case of a 14-year-old female with HbSC disease who presented to the emergency room with complaint of abdominal pain and found to have splenic sequestration. Splenic sequestration progressed rapidly, Hemoglobin (hb) dropped to 4.6 g/dl and acute chest syndrome (ACS) developed. She was treated following the ACS protocol, received 4 units of Packed Red Blood Cells (PRBC) and subsequently underwent a single volume PRBC exchange transfusion. Considering her unusual presentation, with severe ARDS from alveolar hemorrhage requiring mechanical ventilation and multi-organ injury, several autoimmune and infectious conditions with a cytokine storm component including COVID-19 disease, were considered. Results of viral testing revealed parvovirus B19 IgM antibodies signifying an acute infection. She fully recovered with supportive care and was discharged home. Multisystem involvement simulating connective tissue disorders or malignancies with acute parvovirus B19 infection has been reported and is considered extremely rare. To our knowledge, there were no reports of pediatric patients with SC disease presenting with splenic sequestration and ACS in the setting of parvovirus B19 multisystem disease. Keywords: sickle cell disease; acute respiratory distress syndrome; acute chest syndrome; parvovirus B19.

High Survival in Patients with Myelofibrosis Undergoing a Two-Step Approach to Hematopoietic Stem Cell Transplantation (HSCT): Effects of Donor Source and Pre-HSCT Splenic Therapy on Outcomes

Introduction: Hematopoietic stem cell transplant (HSCT) remains the only curative therapy for myelofibrosis (MF). However as compared to other hematologic malignancies, HSCT for MF is associated with an increased risk of graft failure due to a limited marrow niche and splenic sequestration of allogeneic progenitors. We report on engraftment and other outcomes in 12 consecutive patients with MF undergoing matched (M-HSCT) and haplo-identical (HI-HSCT) utilizing a two-step T cell-tolerization approach. Methods: Regardless of donor source, all patients were conditioned with our institution's two-step approach. After reduced intensity conditioning consisting of fludarabine, 2 Gy total body irradiation, thiotepa (n=3) OR busulfan (n=8), and in 1 case myeloablative conditioning with 12 Gy total body irradiation, patients received an unmanipulated donor lymphocyte product (DLI) containing 2 x 108/kg CD3+ cells. After 2 days, cyclophosphamide (CY) 60 mg/kg was administered daily x 2 for bidirectional T cell tolerization. One day after CY completion, a CD34-selected stem cell product was infused. All patients received mycophenolate mofetil and tacrolimus beginning on d-1. Pre-conditioning splenic radiation was added starting in 2017 to decrease splenic sequestration of donor cells. This change affected the last six patients in the analysis. Results: Six patients had primary MF and six patients had secondary MF. Donor source was a HLA matched (n=5, median age 54y, range 44-65) or haploidentical (n=7, median age 66y, range 47-67) relative. Eight patients received pre-HSCT radiation or splenectomy. Outcome data is summarized in the table. Median follow-up is 29 (range 6-95.6) months. Median time to neutrophil and platelet engraftment was 12 (range 9-13) days and 19 (13-40) days respectively. Patients undergoing pre-HSCT splenic therapy recovered platelets more rapidly than those without, median 19 vs 27 days, (p=0.059). All patients ultimately achieved 100% donor chimerism. While there was a trend in the M-HSCT group for higher donor T cell chimerism at d+28 in patients undergoing pre-HSCT splenic therapy, (p=0.083), donor source had the most significant impact on the pace of donor chimerism recovery. All 4 DLIs given in this group for fluctuating donor T cell chimerism occurred in M-HSCT recipients. At d+28 median donor T cell chimerism was 100% (range 91-100) in HI-HSCT versus 92% (range 67-100%) in M-HSCT recipients, (p=0.037). Probability of OS at 3 years was 90%. No patient receiving splenic therapy experienced disease progression. Two patients who received DLI experienced graft versus host disease (GVHD), grade 3 acute GVHD in one and extensive chronic GVHD in the other. Conclusion: HSCT using the two-step approach is associated with rapid engraftment and excellent survival in patients with MF. Pre-HSCT splenic therapy was associated with more rapid platelet recovery. Unlike HI-HSCT, M-HSCT patients receiving RIC conditioning experienced initial fluctuating donor T-cell chimerism, a finding worth further exploration in larger trials. Table Disclosures Gergis: Jazz: Other: Ad board, Speakers Bureau; Astellas: Consultancy, Speakers Bureau; Kite: Speakers Bureau; Mesoblast: Other: Ad Board; Incyte: Speakers Bureau; Merck: Speakers Bureau. Flomenberg:Tevogen: Consultancy, Honoraria.

Late Splenic Sequestration: A Consequence of Early Hydroxyurea Use?

Background: Acute splenic sequestration is a potentially life-threatening complication in patients with sickle cell disease. It is the second leading cause of death in young children with hemoglobin SS/Sβ0 thalassemia (SCD). The incidence approaches 35% during the first two years of life in SCD. Although splenic sequestration can occur in patients with any sickle phenotype, patients with SCD tend to be significantly younger when compared to patients with hemoglobin SC disease. Splenic function may be preserved in children treated with hydroxyurea. We recommend hydroxyurea for all SCD patients diagnosed via newborn screening, with a goal of starting therapy before 12 months of age. With this aggressive approach and potential for maintaining some splenic function, this study evaluates acute splenic sequestration in this young cohort and compares this to institutional and historical controls Methods: We performed a retrospective search of electronic medical records at Children's Minnesota from 1/1/1999 through 12/31/2019 to identify patients with SCD and splenic sequestration. We used a broad array of ICD-9 an ICD-10 codes in order to capture all appropriate patients. Following this initial search, in-depth chart review was performed to identify patients with SCD and confirmed splenic sequestration. Data collected includes age, sex, hydroxyurea use, splenectomy, and hematologic results including hemoglobin F percentage, if available. Student t-tests for independent samples were performed to compare cohorts. This study was granted exemption by our Institutional Review Board. Results: Over this 21 year period, the initial search revealed 151 patients. Of those, 74 had SCD. In-depth chart review found 38 (24M, 14F) of these children were confirmed to have splenic sequestration. Twelve patients started hydroxyurea before 2 years of age at a mean age of 12.6 months, median 11 months (cohort A). Of these, six started hydroxyurea during infancy at a mean and median age of 6.5 months (cohort B). The remaining 26 patients were not on hydroxyurea at the time of splenic sequestration (cohort C). Children in cohorts A and B were significantly older at the time of splenic sequestration compared to patients in cohort C (mean 58 and 45.8 months vs. 14.9 months, p< 0.0001). Conclusions: Children with SCD who start hydroxyurea at a young age may develop splenic sequestration much later in life than previously expected. More study is needed to confirm this finding. It will be important to educate families and healthcare providers about this potential unintended consequence of early hydroxyurea use. Disclosures No relevant conflicts of interest to declare. OffLabel Disclosure: Hydroxyurea use in children with sickle cell disease < 2 years of age

Failure of CD4 T Cell-Deficient Hosts To Control Chronic Nontyphoidal Salmonella Infection Leads to Exacerbated Inflammation, Chronic Anemia, and Altered Myelopoiesis

ABSTRACTImmunocompromised patients are more susceptible to recurrent nontyphoidal Salmonella (NTS) bacteremia. A key manifestation of HIV infection is the loss of CD4 T cells, which are crucial for immunity to Salmonella infection. We characterized the consequences of CD4 T cell depletion in mice where virulent Salmonella establish chronic infection, similar to chronic NTS disease in humans. Salmonella-infected, CD4-depleted 129X1/SvJ mice remained chronically colonized for at least 5 weeks, displaying increased splenomegaly and more severe splenitis than infected mice with CD4 T cells. Mature erythrocytes, immature erythroid cells, and phagocytes accounted for the largest increase in splenic cellularity. Anemia, which is associated with increased mortality in Salmonella-infected humans, was exacerbated by CD4 depletion in infected mice and was accompanied by increased splenic sequestration of erythrocytes and fewer erythropoietic elements in the bone marrow, despite significantly elevated levels of circulating erythropoietin. Splenic sequestration of red blood cells, the appearance of circulating poikilocytes, and elevated proinflammatory cytokines suggest inflammation-induced damage to erythrocytes contributes to anemia and splenic retention of damaged cells in infected animals. Depleting CD4 T cells led to increased myeloid cells in peripheral blood, spleen, and bone marrow, as well as expansion of CD8 T cells, which has been observed in CD4-depleted humans. This work describes a mouse model of Salmonella infection that recapitulates several aspects of human disease and will allow us to investigate the interplay of innate and adaptive immune functions with chronic inflammation, anemia, and susceptibility to Salmonella infection.

Adverse outcome of acute splenic sequestration crisis in pregnancy

Background Acute splenic sequestration crisis, characterized by abrupt fall in hemoglobin, splenomegaly, hypovolemia, and often thrombocytopenia, occurs infrequently in adults with sickle cell disease and extremely rarely during pregnancy. Case A 25-year-old woman with HbSC presented at 33 weeks’ gestation with vaso-occlusive pain. Sudden worsening of abdominal pain and non-reassuring fetal surveillance on day 3 of admission led to emergent delivery. Acute splenic sequestration crisis was the diagnosis of exclusion based on clinical presentation and intra-operative hemoglobin of 37 g/L. Five- and 10-minute Apgar scores were 4. Neonatal brain magnetic resonance imaging revealed significant diffuse white matter abnormalities. Conclusion Acute splenic sequestration crisis in pregnancy must be considered in the differential diagnosis for this patient population as it can evolve rapidly and lead to maternal and fetal compromise.