Acquired Glanzmann Thrombasthenia in a Pediatric Patient with Alagille Syndrome

Introduction/Objective Acquired Glanzmann Thrombasthenia is a rare bleeding disorder that is characterized by inhibition of glycoprotein IIb/IIIa signaling, usually by an autoantibody, leading to an interference in platelet aggregation. Clinically, this disorder presents with spontaneous mucocutaneous bleeding in the setting of a normal platelet count. Acquired Glanzmann Thrombasthenia has been associated with primary immune thrombocytopenic purpura (ITP), several types of hematologic and solid malignancies, solid organ transplants, and other autoimmune disorders. Methods/Case Report A 4-year-old female patient with a history of Alagille Syndrome requiring liver transplant at age 3 was admitted to the hospital after presenting to the emergency department with complaints of bruising, nosebleeds, and a petechial rash. The patient was found to have a platelet count of 11 K/mm3 and was diagnosed with ITP. The patient received a single dose of IVIG at 1g/kg with subsequent resolution of bleeding and a recovering platelet count of 27 K/mm3 12 hours after administration. However, two months later, the patient presented again with worsening bruising, multiple nosebleeds per day, and worsening petechiae. Lab studies revealed the patient’s platelet count was within normal limits. A platelet antibody screen was positive with a subsequent Platelet Antibody Bead Array revealing anti-Gp IIb/IIIa HPA-1 and HPA-3 positivity. Results (if a Case Study enter NA) N/A Conclusion Acquired Glanzmann Thrombasthenia is a rare bleeding disorder that is the result of interference with platelet aggregation. Antibodies that may be associated with any of several underlying conditions lead to impaired platelet function and subsequent mucocutaneous bleeding. The present case represents an occurrence of Acquired Glanzmann Thrombasthenia in a patient with multiple risk factors for development of the disorder.

Evaluation of influence of IL-6 C-572G gene polymorphism and clinical factors on positive platelet antibody test

Background: Interleukin-6 (IL-6) promotes antibody production. The objective of this study was to investigate whether IL-6 C-572G single nucleotide polymorphisms (SNP) and clinical factors are associated with positive platelet antibody test. Materials and methods: Thirty platelet recipients with platelet antibodies (responders) and 20 platelet recipients without platelet antibodies (non-responders) were randomly selected. The -572 C>G (rs 1800796) SNPs in the promoter region of IL-6 gene were genotyped by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method. Solid phase red cell adherence assay (SPRCA) was used for platelet antibody detection. Results: Age, sex, percentage patients with benign diseases, and percentage of patients with homozygotes for the C allele at position -572 of the IL-6 gene were similar between responders and non-responders. Although the amounts of platelets pheresis transfused to patients with hematologic diseases were higher than those of non-hematologic diseases (47.2 ± 54.2 vs. 17.4 ± 13.8 units, p = 0.019), detection rate of platelet antibodies was lower in patients with hematologic diseases than that in patients with non-hematologic diseases (42.3% vs. 79.2%, p = 0.01). Conclusion: There was no association between IL-6 C-572G gene polymorphism and positive reactivity in solid phase platelet antibody detection method in platelet recipients.

A Single Institution's Adherence to Heparin-Induced Thrombocytopenia and Thrombosis Testing Guidelines

Introduction: What was once an under-recognized clinical entity, heparin induced thrombocytopenia and thrombosis (HITT) has become a well-recognized and frequently tested disease. HITT is a serious and potentially fatal antibody mediated drug reaction to platelet factor 4 and early identification and treatment is essential. The 4T score is well-validated to guide appropriate testing of HITT where a low-probability score of 0-3 equates to a 99.8% negative predictive value for HITT2,3. In an effort to promote cost-conscious care and efficient use of healthcare resources, the American Society of Hematology (ASH) recommends against testing for HITT if the 4T score is 3 or less4. HITT laboratory testing at our institution is not restricted based on 4T score. We hypothesize that many providers are not following cost-conscious guidelines regarding HITT testing at our institution. Methods: We performed a single-institution retrospective analysis of patients who had a heparin-induced platelet antibody assay with reflexive serotonin release assay ordered between July 1, 2016 to July 1, 2017 at the University of Virginia Medical Center (UVA). We primarily assessed how our institution's ordering of heparin-induced platelet antibody for HITT compared to ASH's Choosing Wisely recommendation of forgoing laboratory testing on patients with a 4T score of 0-3 by retrospectively calculating 4T scores on all patients who had laboratory testing4. Patients were also assessed for episodes of bleeding and clotting and were scored on severity via the CTCAE and ISTH grading systems. Data on anticoagulant used after HITT testing was collected. We also checked to see if the blood specimen for assay was collected 2 hours after last heparin product as recommended by lab. Patients were excluded if they were not inpatient when their heparin-induced platelet antibody assay was drawn or if they were transferred or discharged immediately after assay was collected. Ultimately, of the initial 196 patients who had heparin-induced platelet antibody assay collected during this time frame, 184 patients were included for analysis. Results: Of the 184 patients who had a heparin-induced platelet antibody assay sent and were included in analysis, 55.4% of the patients (n=102) had a low pre-test probability of HITT with a 4T score of less than or equal to 3. Of the patients who had HITT testing sent, only 44% (n=81) received treatment with a non-heparin anticoagulant. Of the 102 patients who had a low pre-test probability of HITT with a 4T score of ≤3, 37.3% (n=38) were placed on an alternative anticoagulant. Of this low pre-test probability of HITT cohort, 7.8% (n=8) experienced bleeding as a complication. Interestingly, 15.5% (n=29) of all patients who had HITT testing continued to receive heparin products while awaiting results. Additionally, 19.3% (n=36) of samples were drawn within 2 hours of receiving heparin products. Conclusion: The guidelines for HITT testing and treatment have been well-validated and widely disseminated. Despite providers' familiarity with this clinical entity, the results depict that ordering practices at our institution do not follow guidelines in cost-conscious ordering nor in standard of treatment. Applying ASH's Choosing Wisely recommendation of not ordering laboratory testing on patients with a 4T low-probability score of 0-3, we see that 55.6% of the HITT assays ordered in this time period were inappropriate and at a cost of $455 to the institution per assay resulted in $46,865 of unnecessary health care costs to our institution in one year's time. This does not include the cost of alternative anticoagulation. Heparin costs just $0.04 per mL while argatroban costs $3.81 per mL and bivalirudin $12 per mL resulting in a 100 to 300 fold cost increase respectively. Standard work regarding HITT assay collection and treatment does not exist at our institution. Of concern, 15.5% of patients continued to receive heparin products after HITT testing was sent. The results of this study prompted implementation of a quality improvement project to decrease inappropriate HITT testing and standardize treatment of suspected HITT via an electronic medical record order set that uses the 4T score to suggest appropriate ordering of assays. We plan to collect data on changes in our ordering practices after this intervention. Disclosures No relevant conflicts of interest to declare.

Amelioration of Immune Thrombocytopenia in Human CD44 Transgenic Mice By Anti-Human CD44 Antibodies

Selected monoclonal antibodies to murine CD44 are able to successfully ameliorate murine immune thrombocytopenia (ITP) and other inflammatory diseases at a 3 log fold lower dose than IVIg. Since not all murine CD44 antibodies were successful and, like IVIg, the anti-inflammatory mechanism involved is speculative, progress toward human antibodies has been stymied. To potentially develop a therapeutic antibody for patients, we generated transgenic mice expressing the extracellular and transmembrane sequences of human CD44 linked to the murine intracellular CD44 sequence (huCD44) with knockout of murine CD44. Flow cytometric analysis revealed that these mice express huCD44 on leukocytes, but not on platelets or red blood cells. HuCD44 mice injected with the anti-platelet antibody MWReg30 develop significant thrombocytopenia comparable to normal mice. Utilizing the huCD44 mouse model, we tested 5 monoclonal antibodies reactive with human CD44 of different isotypes; mouse IgG1, mouse IgG2a, mouse IgG2b, rat IgG2a, and rat IgG2b. We report here that pretreatment of mice with all of these antibodies, with the exception of the mouse IgG2b clone all ameliorated thrombocytopenia to the same extent as IVIg, but given at a 3 log-fold lower dosage than IVIg. Interestingly, the mouse IgG2b antibody that was not successful bound to white blood cells as well as the successful antibodies. When mice were re-injected with anti-platelet antibody 24 hr post anti-huCD44 antibody injection, they were still protected from thrombocytopenia at 48 hr, suggesting that these antibodies exhibit durable protection. The clinical effectiveness of these antibodies does not appear to be related to their extent of huCD44 binding or IgG subtype. In addition, the effectiveness of these antibodies may not be restricted or related to specific activating IgG Fc receptors (FcγR) as the successful mouse IgG1 subtype is only known to interact with FcγRIII, while the IgG2b subtype can bind activating FcγRI, III and IV with only one-of-two of this subtype having therapeutic activity. In conclusion we have developed, to our knowledge, the first huCD44 transgenic mouse and demonstrate herein that selected antibodies to huCD44 can ameliorate immune thrombocytopenia. These data suggest that some anti-CD44 antibodies may offer a new therapeutic modality for patients with ITP. Disclosures No relevant conflicts of interest to declare.