Pathophysiology and management of primary immune thrombocytopenia

Does the site of platelet sequestration predict the response to splenectomy in adult patients with immune thrombocytopenic purpura?

Splenectomy is the only potentially curative treatment for chronic immune thrombocytopenic purpura (ITP) in adults. However, one-third of the patients relapse without predictive factors identified. We evaluate the predictive value of the site of platelet sequestration on the response to splenectomy in patients with ITP. Eighty-two consecutive patients with ITP treated by splenectomy between 1992 and 2013 were retrospectively reviewed. Platelet sequestration site was studied by (111)Indium-oxinate-labeled platelets in 93% of patients. Response to splenectomy was defined at last follow-up as: complete response (CR) for platelet count (PC) ≥100 × 10(9)/L, response (R) for PC≥30 × 10(9)/L and <100 × 10(9)/L with absence of bleeding, no response (NR) for PC<30 × 10(3)/L or significant bleeding. Laparoscopic splenectomy was performed in 81 patients (conversion rate of 16%), and open approach in one patient. Median follow-up was 57 months (range, 1-235). Platelet sequestration study was performed in 93% of patients: 50 patients (61%) exhibited splenic sequestration, 9 (11%) hepatic sequestration and 14 patients (17%) mixed sequestration. CR was obtained in 72% of patients, R in 25% and NR in 4% (two with splenic sequestration, one with hepatic sequestration). Preoperative PC, age at diagnosis, hepatic sequestration and male gender were significant for predicting CR in univariate analysis, but only age (HR = 1.025 by one-year increase, 95% CI [1.004-1.047], p = 0.020) and pre-operative PC (HR = 0.112 for > 100 versus <=100, 95% CI [0.025-0.493], p = 0.004) were significant predictors of recurrence-free survival in multivariate analysis. Response to splenectomy was independent of the site of platelet sequestration in patients with ITP. Pre-operative platelet sequestration study in these patients cannot be recommended.

A new ibuprofen derivative inhibits platelet aggregation and ROS mediated platelet apoptosis

Thrombocytopenia is a serious issue connected with the pathogenesis of several human diseases including chronic inflammation, arthritis, Alzheimer's disease, cardiovascular diseases (CVDs) and other oxidative stress-associated pathologies. The indiscriminate use of antibiotics and other biological drugs are reported to result in thrombocytopenia, which is often neglected during the treatment regime. In addition, augmented oxidative stress induced by drugs and pathological conditions has also been shown to induce thrombocytopenia, which seems to be the most obvious consequence of elevated rate of platelet apoptosis. Thus, blocking oxidative stress-induced platelet apoptosis would be of prime importance in order to negotiate thrombocytopenia and associated human pathologies. The current study presents the synthesis and platelet protective nature of novel ibuprofen derivatives. The potent anti-oxidant ibuprofen derivative 4f was selected for the study and the platelet protective efficacy and platelet aggregation inhibitory property has been demonstrated. The compound 4f dose dependently mitigates the oxidative stress-induced platelet apoptosis in both platelet rich plasma and washed platelets. The platelet protective nature of compound 4f was determined by assessing various apoptotic markers such as ROS generation, cytosolic Ca2+ levels, PS externalization, cytochrome C translocation, Caspase activation, mitochondrial membrane depolarization, cytotoxicity, LDH leakage and tyrosine phosphorylation of cytosolic proteins. Furthermore, compound 4f dose dependently ameliorated agonist induced platelet aggregation. Therefore, compound 4f can be estimated as a potential candidate in the treatment regime of pathological disorders associated with platelet activation and apoptosis. In addition, compound 4f can be used as an auxiliary therapeutic agent in pathologies associated with thrombocytopenia.

Redox control of platelet functions in physiology and pathophysiology

SIGNIFICANCE

An imbalance between the production and the detoxification of reactive oxygen species and reactive nitrogen species (ROS/RNS) can be implicated in many pathological processes. Platelets are best known as primary mediators of hemostasis and can be either targets of ROS/RNS or generate radicals during cell activation. These conditions can dramatically affect platelet physiology, leading even, as an ultimate event, to the cell number modification. In this case, pathological conditions such as thrombocytosis (promoted by increased cell number) or thrombocytopenia and myelodysplasia (promoted by cell decrease mediated by accelerated apoptosis) can occur.

RECENT ADVANCES

Usually, in peripheral blood, ROS/RNS production is balanced by the rate of oxidant elimination. Under this condition, platelets are in a nonadherent "resting" state. During endothelial dysfunction or under pathological conditions, ROS/RNS production increases and the platelets respond with specific biochemical and morphologic changes. Mitochondria are at the center of these processes, being able to both generate ROS/RNS, that drive redox-sensitive events, and respond to ROS/RNS-mediated changes of the cellular redox state. Irregular function of platelets and enhanced interaction with leukocytes and endothelial cells can contribute to pathogenesis of atherosclerotic and thrombotic events.

CRITICAL ISSUES

The relationship between oxidative stress, platelet death, and the activation-dependent pathways that drive platelet pro-coagulant activity is unclear and deserves to be explored.

FUTURE DIRECTIONS

Expanding knowledge about how platelets can mediate hemostasis and modulate inflammation may lead to novel and effective therapeutic strategies for the long and growing list of pathological conditions that involve both thrombosis and inflammation.

Eltrombopag and high-dose dexamethasone as frontline treatment of newly diagnosed immune thrombocytopenia in adults

Immune thrombocytopenia (ITP) results from platelet destruction and production suppression. Eltrombopag belongs to a new class of thrombopoietin-mimetic drugs that raise platelet counts in ITP patients. We performed a single-arm study to assess the response to a single course of dexamethasone (40 mg by mouth, days 1-4) in combination with eltrombopag (50 mg, days 5-32) in 12 adults with newly diagnosed ITP in an outpatient setting. Median follow-up was 12.5 months. After therapy (day 33), 100% of patients achieved at least ≥30 × 10(9)/L platelets. Four patients relapsed. Complete response at 6 months (platelets ≥100 × 10(9)/L) was achieved in 50% of patients and response at 6 months (platelets ≥30 <100 × 10(9)/L) was achieved in another 25%; relapse-free survival was 66.7% at 12 months (median response duration of 8.3 months). In conclusion, eltrombopag/dexamethasone is a feasible frontline therapy for ITP. This trial is registered at www.clinicaltrials.gov as NCT01652599.

Moxifloxacin-Induced Immune-Mediated Thrombocytopenia in a Chronic Kidney Disease Patient Receiving Hemodialysis

OBJECTIVE

To alert clinicians to a serious complication from a commonly prescribed medication, moxifloxacin.

CASE SUMMARY

A 65-year-old male, septic, hemodialysis patient developed thrombocytopenia following exposure to vancomycin, ceftazidime, and moxifloxacin. Drug-specific immunoglobulin testing showed positive autoantibodies against only moxifloxacin, and the probability stratification proposed by Naranjo et al would give this case a score of 7-a probable association between moxifloxacin and the adverse event.

DISCUSSION

Idiopathic thrombocytopenic purpura (ITP) results in immune-mediated platelet destruction, with bleeding risk frequently manifested by purpuric skin and mucosal lesions. Although many drugs are associated with ITP, moxifloxacin has only been characterized in 2 previous case reports. This is the first case report where specific immunoglobulin antibody testing showed a positive association between ITP and moxifloxacin.

CONCLUSIONS

Moxifloxacin is a commonly prescribed medication because of its wide spectrum of activity, high bioavailability, and convenient dose schedule. Clinicians need to be aware of this little-known side effect of this commonly prescribed antibiotic.

Long-term follow-up of children with refractory immune thrombocytopenia treated with rituximab

Data on long-term outcomes of children with refractory immune thrombocytopenia (ITP) treated with rituximab are limited. We retrospectively analyzed the long-term effect of rituximab on 22 pediatric ITP patients (11 boys and 11 girls). Compete response (CR) (platelet count ≥100 × 10(9)/L) and partial response (PR) (platelet count 30-99 × 10(9)/L) were achieved in nine (41 %) and two (9 %) patients, respectively. Of the 11 responders, eight subsequently relapsed 2-26 months after initial rituximab treatment. The 5-year relapse-free rate was 14 % (3/22, 95 % confidence interval: 0-27 %) with a median follow-up period of 6.4 years. Five initial responders with subsequent relapse and one non-responder received multiple rituximab treatments of nine courses; all patients responded to the second rituximab therapy without any significant toxicity. All eight patients who relapsed after an initial response and six of 11 non-responders achieved CR or PR with subsequent treatment, including repeated courses of rituximab, splenectomy, steroids, and other immunomodulating agents. Our findings indicated that the sustained effect of rituximab on children with refractory ITP is low, but that the long-term outcome of ITP itself is not poor. Furthermore, repeated rituximab administration may be a promising therapy for those who relapse after an initial response.

Current management of immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune-mediated condition that results from antibody-mediated destruction of platelets and impaired megakaryocyte platelet production. ITP patients exhibit severe thrombocytopenia and are at risk for significant hemorrhage. Few randomized trials exist to guide management of patients with ITP. Ultimately, each patient requires an individualized treatment plan that takes into consideration the platelet count, bleeding symptoms, health-related quality of life, and medication side effects. This article provides an up-to-date review of management strategies drawing on links between the expanding amounts of clinical trial data and associated biology studies to enhance understanding of the disease heterogeneity with regard to the complex pathogenesis and response to treatment.