Thrombotic thrombocytopenic purpura: A 5-year tertiary care centre experience

Autoantibodies to ADAMTS13 in human immunodeficiency virus-associated thrombotic thrombocytopenic purpura

BACKGROUND AND OBJECTIVES

Thrombotic thrombocytopenic purpura (TTP) is a potentially fatal thrombotic microangiopathic disorder that can result from human immunodeficiency virus (HIV) infection. The pathogenesis involves a deficiency of the von Willebrand factor (vWF) cleaving protease ADAMTS13 (a disintegrin and metalloprotease with thrombospondin motifs member 13) and the presence of anti-ADAMTS13 autoantibodies. However, there is insufficient information regarding the epitope specificity and reactivity of these autoantibodies. This study aimed to perform epitope-mapping analysis to provide novel insights into the specific epitopes on ADAMTS13 domains affected by autoantibodies.

MATERIALS AND METHODS

The study analysed 59 frozen citrate plasma samples from HIV-associated TTP patients in South Africa, measuring ADAMTS13 activity using Technozyme® ADAMTS13 activity test, total immunoglobulin (Ig) M and IgA antibodies levels using ELISA kit and purifying IgG antibodies using NAb™ Protein G spin columns. A synthetic ADAMTS13 peptide library was used for epitope mapping.

RESULTS

Overall, 90% of samples showed anti-ADAMTS13 IgG autoantibodies, with 64% of these antibodies being inhibitory, as revealed by mixing studies. Samples with ADAMTS13 antigen levels below 5% showed high anti-ADAMTS13 IgG autoantibody titres (≥50 IU/mL), whereas those with 5%-10% levels had low autoantibody titres (<50 IU/mL).The metalloprotease, cysteine-rich and spacer domains were 100% involved in binding anti-ADAMTS13 IgG antibodies, with 58% of samples containing antibodies binding to the C-terminal part of the ADAMTS13 disintegrin-like domain, indicating different pathogenic mechanisms.

CONCLUSION

The metalloprotease, cysteine-rich and spacer domains are the primary targets for anti-ADAMTS13 IgG autoantibodies in patients with HIV-associated TTP. These findings suggest potential effects on the proteolytic activity of ADAMTS13, highlighting the complex nature of the pathogenic mechanisms involved.

HIV-Associated Thrombotic Thrombocytopenic Purpura in a Virally Suppressed Patient With Normal CD4 Count: A Rare Presentation

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic process characterized by multiorgan failure secondary to microvascular thrombi comprising platelets and von Willebrand factor. HIV is a known risk factor for TTP. However, patients generally have low CD4+ count during initial presentation or subsequent flare-ups. This case report describes a 69-year-old man with HIV who presented with an initial presentation of TTP while having a prior history of HIV with a normal CD4 count and undetectable viral load on presentation. A 69-year-old Caucasian male with a previous history of HIV on antiretroviral therapy (ART), a history of recurrent deep vein thrombosis maintained on Coumadin, and no previous history of tobacco dependence or substance use presented to the emergency department with symptoms of fatigue and dyspnea worsening on exertion. The patient had stable vital signs on arrival. The initial lab workup was remarkable for hemoglobin of 9.3 g/dL, hematocrit 29%, platelets 22 x 109/L, prothrombin time (PT) 51 seconds, activated partial thromboplastin time (PTT) 41 seconds, international normalized ratio (INR) 4.3 (on warfarin), blood urea nitrogen (BUN) 29 mg/dL, creatinine 2.0 mg/dL, total bilirubin 1.8 mg/dL, lactate dehydrogenase (LDH) 1229 U/L, haptoglobin less than 10 mg/dL, reticulocyte count 6.21%, fibrinogen 519 mg/dL, and D-dimer within normal limits. A clinical diagnosis of TTP was made with a peripheral blood smear showing schistocytes, as well as evidence of hemolytic anemia and thrombocytopenia. Prompt initiation of treatment with plasma exchange therapy was started. The patient was also given high-dose steroids and prednisone 1 mg/kg with a prolonged taper. Due to the delay in improvement in platelet count, the patient was also given concurrent rituximab therapy. TTP in HIV is rare, primarily seen in HIV patients who have a high viral load, low CD4 count, or if there is a delay in starting ART. In HIV-induced TTP patients, the relationship between CD4 count and viral load is complex and not fully elucidated. Further research is needed to understand better the interplay between HIV parameters (such as CD4 count and viral load) and the development of TTP in HIV-infected individuals who are already on treatment. This understanding could aid in identifying high-risk patients and developing targeted interventions to prevent or manage TTP in this population.

A Rare Intersection: Managing Thrombotic Thrombocytopenic Purpura in the Context of Dengue Fever

Thrombotic thrombocytopenic purpura (TTP) is a rare, life-threatening condition that can lead to severe morbidity and mortality if untreated. This case report discusses a 31-year-old male with dengue fever who developed TTP, resulting in fatality despite timely diagnosis and comprehensive treatment. The patient presented with worsening symptoms, including body aches, gastrointestinal bleeding, and neurological issues. Initial treatment focused on managing dengue hemorrhagic fever, but TTP was later suspected, leading to the cessation of platelet transfusions and initiation of plasma exchange, steroids, and rituximab. Despite these efforts, the patient's condition deteriorated. This case underscores the challenges in managing TTP, especially when triggered by infections like dengue. The use of the PLASMIC score can be highly effective in suspecting TTP in these patients, allowing for the initiation of early management. While standard treatments include plasma exchange and immunosuppressive therapy, emerging treatments such as caplacizumab and the potential use of splenectomy may offer hope for better outcomes in the future.

Thrombotic thrombocytopaenic purpura in the era of HIV: A single-centre experience

Background

Thrombotic thrombocytopaenia purpura (TTP) is a rare disorder which carries a high mortality. HIV is an important cause of TTP.

Objectives

We assessed the presentation and response to plasma exchange (PEX) by HIV status.

Method

A single-centre retrospective review of all patients receiving PEX for TTP between 01 January 2010 and 31 December 2019 was undertaken. Demographics and presenting parameters were compared between HIV-associated TTP and other aetiologies using Mann-Whitney U and Kruskal Wallis analysis of variance testing, as appropriate. The effect of aetiology and presenting parameters on PEX duration was modelled using Cox proportional hazards; effect of these variables on mortality and residual renal dysfunction in survivors was analysed using stepwise multivariate regression.

Results

Uncontrolled HIV infection was the commonest cause (81.9%) of TTP in the 83 patients identified. Thrombocytopaenia was more severe and neurological deficit more frequent in HIV-associated TTP; but renal dysfunction was milder in this group. Aetiology did not influence mortality risk. Aetiological category and presenting parameters did not predict PEX duration. Residual renal dysfunction was less frequent in survivors of HIV-associated TTP.

Conclusion

HIV is an important cause of TTP in the local context. Haematological and neurological involvement are more severe in HIV-associated TTP. Acceptable survival rates are achievable with PEX even in advanced HIV infection; renal sequalae are less common in this group.

HIV-associated thrombotic thrombocytopenic purpura (HIV-TTP): A practical guide and review of the literature

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP), a serious thrombotic microangiopathy (TMA), is prevalent in the South African HIV-infected population. The exact pathogenesis of HIV-associated TTP (HIV-TTP) is however still unclear with diagnostic and therapeutic inconsistancies.

METHODS

A systematic review of the published literature regarding HIV-TTP was performed.

RESULTS

HIV-TTP is still associated with significant morbidity and mortality in Africa despite the availability of anti-retroviral therpy (ART). Diagnosis of HIV-TTP requires the presence of a micro-angiopathic haemolytic anaemia with significant red blood cell schistocytes and thrombocytopenia in the absence of another TMA but background activation of the coagulation system and inflammation in HIV infected people can result in diagnostic anbiguity. Plasma therapy in the form of infusion or exchange is successful but expensive, associated with side-effects and not widely available. Adjuvant immunosuppression therapy may of benefit in patients with HIV-TTP and ART must always be optimised. Endothelial dysfunction caused by chronic inflammation and complement activation most likely contributes to the development of HIV-TTP.

CONCLUSION

The role of adjuvant immunomodulating therpy, the therapeutic targets and pathogenic contribution from endothelial dysfunction in HIV-TTP requires further investigation.

Incidence of thrombotic microangiopathies in Quebec: insight from a laboratory centralizing ADAMTS-13 testing

BACKGROUND

Thrombotic microangiopathies (TMA) are serious medical conditions requiring a prompt diagnosis to adapt treatment. The determination of ADAMTS-13 activity enables discriminating thrombotic thrombocytopenic purpura (TTP) from other forms of TMA. The purpose of this study was to provide an estimate of the incidence of TTP and TMA in the Canadian Quebec province using data collected from a laboratory centralizing ADAMTS-13 testing for the whole province.

RESULTS

From 2012 to 2019, 846 patients were evaluated for plasma ADAMTS-13 activity due to a suspicion of TMA. TTP was identified in 147 patients. Of these, 118 patients with a median age of 51.5 years and a male-female ratio of 1:1.4 had their first episode of TTP during the study period. The number of ADAMTS-13 tests performed and the number of patients with suspected TMA increased annually by 19% and 21% respectively. While the incidence of non-TTP TMA increased annually, that for TTP remained unchanged. This averaged 10.2 (95% CI 5.9-14.4) per million persons per year for suspected non-TTP TMA and 1.8 (95% CI 1.3-2.4) for confirmed TTP. The incidence rate of TMA other than TTP was higher in the age group 70-79 years (21.8; 95% CI 5.4-38.1) for females and in the age group 80-89 years (24.4; 95% CI 7.2-41.7) for males compared to other age groups. The incidence rate of TTP was higher in the age group 40-49 years (4.0; 95% CI 2.0-5.9) for women and in the age group 60-69 years (3.4; 95% CI 1.1-5.6) for men compared to other age groups.

CONCLUSION

The analysis of centralized data measuring ADAMTS-13 activity allowed us to adequately establish the incidence rate and demographic characteristics of TMA, particularly TTP, in Quebec. TTP incidence remained stable while suspected non-TTP TMA steadily increased from 2012 to 2019.

Complement in Secondary Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) is a condition characterized by thrombocytopenia and microangiopathic hemolytic anemia (MAHA) with varying degrees of organ damage in the setting of normal international normalized ratio and activated partial thromboplastin time. Complement has been implicated in the etiology of TMA, which are classified as primary TMA when genetic and acquired defects in complement proteins are the primary drivers of TMA (complement-mediated TMA or atypical hemolytic uremic syndrome, aHUS) or secondary TMA, when complement activation occurs in the context of other disease processes, such as infection, malignant hypertension, autoimmune disease, malignancy, transplantation, pregnancy, and drugs. It is important to recognize that this classification is not absolute because genetic variants in complement genes have been identified in patients with secondary TMA, and distinguishing complement/genetic-mediated TMA from secondary causes of TMA can be challenging and lead to potentially harmful delays in treatment. In this review, we focus on data supporting the involvement of complement in aHUS and in secondary forms of TMA associated with malignant hypertension, drugs, autoimmune diseases, pregnancy, and infections. In aHUS, genetic variants in complement genes are found in up to 60% of patients, whereas in the secondary forms, the finding of genetic defects is variable, ranging from almost 60% in TMA associated with malignant hypertension to less than 10% in drug-induced TMA. On the basis of these findings, a new approach to management of TMA is proposed.

Understanding the Health Literacy in Patients With Thrombotic Thrombocytopenic Purpura

Following an acute thrombotic thrombocytopenic purpura (TTP) episode, patients are at risk for relapse, and a careful long-term follow-up is needed. Adherence to the follow-up by patients implies a good understanding of the disease. However, TTP literacy in patients is currently unknown. To explore the TTP literacy in patients and identify factors associated with poor disease understanding, a questionnaire was developed focusing on patient's characteristics, knowledge about TTP and patients' actions in an emergency. The questionnaire was presented to 120 TTP patients in remission from the French National Registry for Thrombotic Microangiopathies. TTP literacy was low in 24%, intermediate in 43% and high in 33% of the patients. Low TTP literacy was associated with older age and low education level. Among the knowledge gaps identified, few patients knew that plasma exchange in acute phase is mandatory and has to be done daily (39%), 47% of participants did not consider themselves at risk for relapse, and 30% of women did not know that pregnancy exposes them to a greater risk of relapse. Importantly, few patients responded about life-saving actions in an emergency. Hence, the design of educational material should pay special attention to the age and education level of the target population focusing on the events leading to TTP, the importance of the emergency treatment, controllable predisposing factors for TTP development and patient attitude in an emergency.