HIV-associated thrombotic microangiopathy in the era of highly active antiretroviral therapy: an observational study

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.

Platelet and HIV Interactions and Their Contribution to Non-AIDS Comorbidities

Platelets are anucleate cytoplasmic cell fragments that circulate in the blood, where they are involved in regulating hemostasis. Beyond their normal physiologic role, platelets have emerged as versatile effectors of immune response. During an infection, cell surface receptors enable platelets to recognize viruses, resulting in their activation. Activated platelets release biologically active molecules that further trigger host immune responses to protect the body against infection. Their impact on the immune response is also associated with the recruitment of circulating leukocytes to the site of infection. They can also aggregate with leukocytes, including lymphocytes, monocytes, and neutrophils, to immobilize pathogens and prevent viral dissemination. Despite their host protective role, platelets have also been shown to be associated with various pathophysiological processes. In this review, we will summarize platelet and HIV interactions during infection. We will also highlight and discuss platelet and platelet-derived mediators, how they interact with immune cells, and the multifaceted responsibilities of platelets in HIV infection. Furthermore, we will give an overview of non-AIDS comorbidities linked to platelet dysfunction and the impact of antiretroviral therapy on platelet function.

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.

Heme-Induced Macrophage Phenotype Switching and Impaired Endogenous Opioid Homeostasis Correlate with Chronic Widespread Pain in HIV

Chronic widespread pain (CWP) is associated with a high rate of disability and decreased quality of life in people with HIV-1 (PWH). We previously showed that PWH with CWP have increased hemolysis and elevated plasma levels of cell-free heme, which correlate with low endogenous opioid levels in leukocytes. Further, we demonstrated that cell-free heme impairs β-endorphin synthesis/release from leukocytes. However, the cellular mechanisms by which heme dampens β-endorphin production are inconclusive. The current hypothesis is that heme-dependent TLR4 activation and macrophage polarization to the M1 phenotype mediate this phenomenon. Our novel findings showed that PWH with CWP have elevated M1-specific macrophage chemokines (ENA-78, GRO-α, and IP-10) in plasma. In vitro, hemin-induced polarization of M0 and M2 macrophages to the M1 phenotype with low β-endorphins was mitigated by treating cells with the TLR4 inhibitor, TAK-242. Similarly, in vivo phenylhydrazine hydrochloride (PHZ), an inducer of hemolysis, injected into C57Bl/6 mice increased the M1/M2 cell ratio and reduced β-endorphin levels. However, treating these animals with the heme-scavenging protein hemopexin (Hx) or TAK-242 reduced the M1/M2 ratio and increased β-endorphins. Furthermore, Hx attenuated heme-induced mechanical, heat, and cold hypersensitivity, while TAK-242 abrogated hypersensitivity to mechanical and heat stimuli. Overall, these results suggest that heme-mediated TLR4 activation and M1 polarization of macrophages correlate with impaired endogenous opioid homeostasis and hypersensitivity in people with HIV.

Atypical hemolytic uremic syndrome in a patient with HIV treated with eculizumab: A case report

Thrombotic microangiopathy defines a group of pathologies characterized by microvascular dysfunction with the concurrence of microangiopathic hemolytic anemia, thrombocytopenia, and organ damage. It represents the most frequent microvascular manifestation of human immunodeficiency virus (HIV) infection. We report the case of a man in the seventh decade of life with a recent diagnosis of infection by HIV, who develops hemolytic uremic syndrome, requiring continuous renal replacement therapy and plasma replacement therapy, without response, ADAMTS13 with preserved activity, ruling out other etiologies (infectious, metabolic, and genetic) with successful response to eculizumab.

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.

Virus-Associated Nephropathies: A Narrative Review

While most viral infections cause mild symptoms and a spontaneous favorable resolution, some can lead to severe or protracted manifestations, specifically in immunocompromised hosts. Kidney injuries related to viral infections may have multiple causes related to the infection severity, drug toxicity or direct or indirect viral-associated nephropathy. We review here the described virus-associated nephropathies in order to guide diagnosis strategies and treatments in cases of acute kidney injury (AKI) occurring concomitantly with a viral infection. The occurrence of virus-associated nephropathy depends on multiple factors: the local epidemiology of the virus, its ability to infect renal cells and the patient's underlying immune response, which varies with the state of immunosuppression. Clear comprehension of pathophysiological mechanisms associated with a summary of described direct and indirect injuries should help physicians to diagnose and treat viral associated nephropathies.

Diagnosis and treatment of thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is characterized by thrombocytopenia, microangiopathic haemolytic anaemia and end organ damage. TMAs have varying underlying pathophysiology and can therefore present with an array of clinical presentations. Renal involvement is common as the kidney is particularly susceptible to the endothelial damage and microvascular occlusion. TMAs require rapid assessment, diagnosis, and commencement of appropriate treatment due to the high morbidity and mortality associated with them. Ground-breaking research into the pathogenesis of TMAs over the past 20 years has driven the successful development of targeted therapeutics revolutionizing patient outcomes. This review outlines the clinical presentations, pathogenesis, diagnostic tests and treatments for TMAs.

Indications and diagnostic value of bone marrow examination in HIV-positive individuals: A 3-year review at Tygerberg Hospital

Background

Bone marrow examination is a useful diagnostic tool in human immunodeficiency virus (HIV)-positive patients presenting with cytopenias and fever. However, its role in the afebrile and asymptomatic patient presenting with an isolated cytopenia is not well established. This study was conducted to determine the indications for bone marrow examination and its diagnostic yield, in HIV-positive patients at Tygerberg Hospital.

Methods

A retrospective, cross-sectional descriptive study was performed over a 3-year period from 01 September 2015 to 31 August 2018. The bone marrow examination reports for the HIV-positive patients who had a bone marrow examination during the study period were retrieved. Clinical and laboratory information was captured.

Results

Altogether 374 bone marrow reports for HIV-positive patients were found. The indication of the bone marrow examination included investigation of unexplained cytopenias, suspected haematological malignancies, follow-up examination for patients with known haematological diseases, staging of haematological or non-haematological malignancies and investigation of suspected disseminated infection. The patients' median age was 43 years and the interquartile range was 27-60 years. There was a slight female predominance with females 51% and males 49%. The diagnostic yield was 33.7%. Acute leukaemia and lymphoma were the most common diagnoses. Haematinic deficiency and pure red cell aplasia were found in the majority of cases with isolated anaemia. All cases with isolated thrombocytopenia were due to immune thrombocytopenia.

Conclusion

Bone marrow examination is a useful investigation for HIV-positive patients with cytopenias, suspected haematological malignancy and lymphoma staging. However, its early use in patients with isolated anaemia and isolated thrombocytopenia is questionable.

Infection in Patients with Suspected Thrombotic Microangiopathy Based on Clinical Presentation

BACKGROUND AND OBJECTIVES

In contrast to shigatoxin-associated Escherichia coli (STEC) causing hemolytic uremic syndrome, STEC-unrelated infections associated with thrombotic microangiopathy are less characterized.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our retrospective study in a four-hospital institution of 530 consecutive patients with adjudicated thrombotic microangiopathies during the 2009-2016 period studied STEC-unrelated infections' epidemiology and major outcomes (death, acute dialysis, and major cardiovascular events).

RESULTS

STEC-unrelated infection was present in 145 of 530 (27%) patients, thrombotic microangiopathies without infection were present in 350 of 530 (66%) patients, and STEC causing hemolytic and uremic syndrome was present in 35 of 530 (7%) patients. They (versus thrombotic microangiopathy without infection) were associated with age >60 years (36% versus 18%), men (53% versus 27%), altered consciousness (32% versus 11%), mean BP <65 mm Hg (21% versus 4%), lower hemoglobin and platelet count, and AKI (72% versus 49%). They were associated with more than one pathogen in 36 of 145 (25%) patients (either isolated [14%] or combined [86%] to other causes of thrombotic microangiopathy); however, no significant clinical or biologic differences were noted between the two groups. They were more frequently due to bacteria (enterobacteria [41%], Staphylococcus aureus [11%], and Streptococcus pneumonia [3%]) than viruses (Epstein-Barr [20%], cytomegalovirus [18%], influenza [3%], hepatitis C [1%], HIV [1%], and rotavirus [1%]). STEC-unrelated infections were independent risk factors for in-hospital death (odds ratio, 2.22; 95% confidence interval, 1.18 to 4.29), major cardiovascular event (odds ratio, 3.43; 95% confidence interval, 1.82 to 6.69), and acute dialysis (odds ratio, 3.48; 95% confidence interval, 1.78 to 7.03). Bacteria (versus other pathogens), and among bacteria, enterobacteria, presence of more than one bacteria, and E. coli without shigatoxin were risk factors for acute dialysis.

CONCLUSIONS

Infections are frequent thrombotic microangiopathy triggers or causes, and they are mostly unrelated to STEC. Infections convey a higher risk of death and major complications. The most frequent pathogens were enterobacteria, S. aureus, Epstein-Barr virus, and cytomegalovirus.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_09_07_CJN17511120.mp3.

Acquired Thrombotic Thrombocytopenic Purpura in a Newly Diagnosed HIV Patient: A Case Report and Literature Review

Thrombotic thrombocytopenic purpura (TTP) is a rare but a potentially fatal condition. Although the majority of TTP cases are of unknown etiology, certain viral infections, malignancies, and medications have been linked to the acquired form of the illness. Regardless of the underlying etiology, TTP remains a great challenge diagnostically and therapeutically. TTP remains a very uncommon complication of HIV. We reviewed the current literature to better understand the relationship between HIV and TTP and address some of the major obstacles that may impede or delay the correct diagnosis. Here, we present a case of a 28-year-old male with complaints of light-headedness, fatigue, and gingival bleeding. He was found to have severe anemia and thrombocytopenia. He tested positive for the HIV and was then diagnosed with TTP. Despite needing endotracheal intubation for airway protection, he clinically improved with packed red blood cells, plasmapheresis, and highly active antiretroviral therapy.

Pharmacotherapeutic options for kidney disease in HIV positive patients

INTRODUCTION

Since the developmentof combined antiretroviral therapy (cART), HIV-associated mortality and the incidence of HIV-associated end-stage kidney disease (ESKD) has decreased. However, in the United States, an increase in non-HIV-associated kidney diseases within the HIV-positive population is expected.

AREAS COVERED

In this review, the authors highlight the risk factors for kidney disease within an HIV-positive population and provide the current recommendations for risk stratification and for the monitoring of its progression to chronic kidney disease (CKD), as well as, treatment. The article is based on literature searches using PubMed, Medline and SCOPUS.

EXPERT OPINION

The authors recommend clinicians (1) be aware of early cART initiation to prevent and treat HIV-associated kidney diseases, (2) be aware of cART side effects and discriminate those that may become more nephrotoxic than others and require dose-adjustment in the setting of eGFR ≤ 30ml/min/1.73m², (3) follow KDIGO guidelines regarding screening and monitoring for CKD with a multidisciplinary team of health professionals, (4) manage other co-infections and comorbidities, (5) consider changing cART if drug induced toxicity is established with apparent eGFR decline of ≥ 10ml/min/1.73m² or rising creatinine (≥0.5mg/dl) during drug-drug interactions, and (6) strongly consider kidney transplant in appropriately selected individuals with end stage kidney failure.

Heme attenuates beta-endorphin levels in leukocytes of HIV positive individuals with chronic widespread pain

The prevalence of chronic widespread pain (CWP) in people with HIV is high, yet the underlying mechanisms are elusive. Leukocytes synthesize the endogenous opioid, β-endorphin, within their endoplasmic reticulum (ER). When released into plasma, β-endorphin dampens nociception by binding to opioid receptors on sensory neurons. We hypothesized that the heme-dependent redox signaling induces ER stress, which attenuates leukocyte β-endorphins levels/release, thereby increasing pain sensitivity in people with HIV. Results demonstrated that HIV positive individuals with CWP had increased plasma methemoglobin, erythrocytes membrane oxidation, hemolysis, and low plasma heme scavenging enzyme, hemopexin, compared to people with HIV without CWP and HIV-negative individuals with or without pain. In addition, the leukocytes from people with HIV with CWP had attenuated levels of the heme metabolizing enzyme, heme oxygenase-1, which metabolizes free heme to carbon-monoxide and biliverdin. These individuals also had elevated ER stress, and low β-endorphin in leukocytes. In vitro, heme exposure or heme oxygenase-1 deletion, decreased β-endorphins in murine monocytes/macrophages. Treating cells with a carbon-monoxide donor or an ER stress inhibitor, increased β-endorphins. To mimic hemolytic effects in a preclinical model, C57BL/6 mice were injected with phenylhydrazine hydrochloride (PHZ). PHZ increased cell-free heme and ER stress, decreased leukocyte β-endorphin levels and hindpaw mechanical sensitivity thresholds. Treatment of PHZ-injected mice with hemopexin blocked these effects, suggesting that heme-induced ER stress and a subsequent decrease in leukocyte β-endorphin is responsible for hypersensitivity in people with HIV.

Haemolytic uremic syndrome: diagnosis and management

The thrombotic microangiopathies (TMAs) are a group of diseases characterised by microangiopathic haemolysis, thrombocytopenia, and thrombus formation leading to tissue injury. Traditionally, TMAs have been classified as either thrombotic thrombocytopenic purpura (TTP) or haemolytic uremic syndrome (HUS) based on the clinical presentation, with neurological involvement predominating in the former and acute kidney injury in the latter. However, as our understanding of the pathogenesis of these conditions has increased, it has become clear that this is an over-simplification; there is significant overlap in the clinical presentation of TTP and HUS, there are different forms of HUS, and TMAs can occur in other, diverse clinical scenarios. This review will discuss recent developments in the diagnosis of HUS, focusing on the different forms of HUS and how to diagnose and manage these potentially life-threatening diseases.

Thrombotic thrombocytopenic purpura (TTP)-like syndrome in the HIV era

Background

The thrombotic microangiopathies (TMAs) is a heterogeneous group of relatively uncommon but serious disorders presenting with thrombocytopenia and microangiopathic haemolysis. Thrombotic thrombocytopenic purpura (TTP) is one of these microangiopathic processes. HIV infection is an acquired cause of TTP but the pathogenesis is poorly understood. HIV-associated TTP was previously described to be associated with advanced immunosuppression. The incidence of HIV-related TTP was expected to decline with access to anti-retroviral therapy (ART).

Methods

We undertook an observational study of patients with a diagnosis of TTP admitted to our hospital (CMJAH). The patient demographics, laboratory test results and treatment outcomes were recorded.

Results

Twenty-one patients were admitted with a diagnosis of TTP during the study period. All patients had schistocytes and severe thrombocytopaenia. The presenting symptoms were non-specific and renal dysfunction and neurological compromise were uncommon. 77% of the patients were HIV-infected and, in 7 patients, TTP was the index presentation. The remainder of the HIV infected patients were on ART and the majority were virologically suppressed. A significant female preponderance was present. Only 4 of the 21 patients tested HIV negative with a positive Coombs test in 2. All patients in this cohort received treatment with plasma exchange therapy for a median period of 12 days with a 96.5% survival rate. Neither the baseline laboratory features nor the degree of immunosuppression was predictive of the duration of therapy needed for remission.

Conclusion

HIV-related TTP is still a cause of morbidity and the clinical presentation is heterogeneous which may present a diagnostic challenge in the absence of sensitive biomarkers. Early treatment with plasma exchange is effective but expensive and invasive.

Acute kidney injury in HIV-infected patients: a critical review

Acute kidney injury (AKI) is characterized by a rapid decline of renal function associated with worse outcomes. The purpose of the authors is to perform a critical review of the incidence, risk factors, pathogenesis and outcome of AKI in HIV-infected patients. Human immunodeficiency virus (HIV)-infected patients have an increased risk of developing AKI, to which contribute both HIV-dependent and HIV-independent factors as well as the nephrotoxicity of drugs used. The increased risk of AKI in HIV-infected patients and its negative impact on prognosis highlights the need for identification of patients at risk, creation of prevention strategies and management. HIV-infected patients have an increased risk of developing AKI, to which both HIV-dependent and HIV-independent factors contribute, as well as the nephrotoxicity of drugs used. The increased risk of AKI in HIV-infected patients and its negative impact on prognosis highlight the need for identification of patients at risk, creation of prevention strategies and management.

The Differential Diagnosis and Treatment of Thrombotic Microangiopathies

BACKGROUND

Thrombotic microangiopathies are rare, life-threatening diseaseswhose care involves physicians from multiple specialties. The past five years haveseen major advances in our understanding of the pathophysiology, classification,and treatment of these conditions. Their timely diagnosis and prompt treatment cansave lives.

METHODS

This review is based on pertinent articles published up to 17 December2017 that were retrieved by a selective search of the National Library of Medicine'sPubMed database employing the terms "thrombotic microangiopathy," "thromboticthrombocytopenic purpura," "hemolytic-uremic syndrome," "drug-induced TMA," and"EHEC-HUS."

RESULTS

The classic types of thrombotic microangiopathy are thrombotic thrombo -cytopenic purpura (TTP) and typical hemolytic-uremic syndrome (HUS), also knownas enterohemorrhagic Escherichia coli-associated HUS (EHEC-HUS). There are anumber of further types from which these must be differentiated. The key test,beyond a basic hematological evaluation including a peripheral blood smear, ismeasurement of the blood level of the protease that splits von Willebrand factor,which is designated ADAMTS13 (a disintegrin and metalloprotease with thrombo -spondin type 1 motif, member 13). The quantitative determination of ADAMTS13, ofADAMTS13 activity, and of the ADAMTS13 inhibitor serves to differentiate TTP fromother types of thrombotic microangiopathy. As TTP requires urgent treatment,plasmapheresis should be begun as soon as TTP is suspected on the basis of afinding of hemolysis with schistocytes and thrombocytopenia. The treatment shouldbe altered as indicated once the laboratory findings become available.

CONCLUSION

Rapid differential diagnosis is needed in order to determine the specifictype of thrombotic microangiopathy that is present, because only patients with TTPand only a very small percentage of those with atypical hemolytic-uremic syndrome(aHUS) can benefit from plasmapheresis. The establishment of a nationwideregistry in Germany with an attached biobank might help reveal yet unknowngenetic predispositions.

Pathogenic factors associated with development of disseminated intravascular coagulopathy (DIC) in a tertiary academic hospital in South Africa

Introduction

Disseminated intravascular coagulopathy (DIC) is a thrombotic microangiopathy arising from consumption of both coagulation factors and platelets. DIC is triggered by a number of clinical conditions including severe infection, trauma and obstetric complications. Early diagnosis and treatment of the underlying condition is paramount. A high clinical index of suspicion is needed to ensure that patients at risk of developing DIC are appropriately investigated.

Methods

In order to establish the clinical conditions most frequently associated with DIC, we reviewed all DIC screens received at a tertiary hospital in Johannesburg, South Africa over a 1 year period.

Results

The commonest clinical condition associated with DIC in our population was infection with 84% of patients infected with an identified pathogen. The most frequently diagnosed pathogen was HIV followed by Mycobacterium tuberculosis and other bacterial infections. In the majority of cases, bacteria were isolated from blood cultures. In 47 patients, HIV was the only pathogen which could be isolated. A relative risk ratio of 2.73 and an odds ratio of 29.97 was attributed to HIV for development of a DIC. A malignancy was present in 51 of the patients of which approximately 60% had co-existing infection. No cause could be attributed in 30 patients.

Conclusion

Infection was identified in the majority of the patients diagnosed with DIC in this study. HIV showed the highest relative risk ratio of all pathogens although previous studies have not suggested that HIV was strongly associated with DIC. In almost half of the HIV infected patients, there was no other pathogen isolated despite extensive investigation. This suggests that HIV has a strong association with the development of DIC, warranting further research into the relationship between HIV and disseminated microvascular thrombosis.

Thrombotic Microangiopathy and the Kidney

Thrombotic microangiopathy can manifest in a diverse range of diseases and is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and organ injury, including AKI. It can be associated with significant morbidity and mortality, but a systematic approach to investigation and prompt initiation of supportive management and, in some cases, effective specific treatment can result in good outcomes. This review considers the classification, pathology, epidemiology, characteristics, and pathogenesis of the thrombotic microangiopathies, and outlines a pragmatic approach to diagnosis and management.

Thrombotic microangiopathy in the setting of human immunodeficiency virus infection: High incidence of severe thrombocytopenia

BACKGROUND

Human immunodeficiency virus (HIV) infection increases the risk of thrombotic microangiopathy (TMA), but TMA in the setting of HIV infection is not well characterized. The experience with TMA in the setting of HIV infection at the University of Maryland Medical Center was reviewed.

STUDY DESIGN AND METHODS

Patients undergoing therapeutic plasma exchange (TPE) for TMA from January 1, 2000 through December 31, 2012 were reviewed. Those with known HIV-positive and -negative status were compared.

RESULTS

Among 102 patients with known HIV status, 28 (27%) were HIV-positive, including 3 with previously undiagnosed HIV. HIV-positive patients had a median viral load of 89 500 copies/mL (range, 0->750 000 copies/mL) and a median CD4 count of 58 cells/µL (range, 2-410 cells/µL). Compared to HIV-negative patients, HIV-positive patients more frequently presented with concurrent infections (60.7% vs. 23.7%; P = .0007), had a trend toward lower median platelet counts (3000/µL vs. 15 000/µL; P = .07) and more frequently had platelet counts less than 10 000/mcL (P = .02). Nevertheless, number of TPE procedures required for remission, remission rate, mortality, and relapse incidence were similar in HIV-positive and HIV-negative patients.

CONCLUSIONS

The incidence described herein of HIV infection among TMA patients is the highest reported outside of South Africa. More severe thrombocytopenia in HIV-positive patients may reflect TMA in the setting of preexisting HIV-associated thrombocytopenia. HIV should be considered in patients with TMA, and TMA should be considered in HIV-positive patients with severe thrombocytopenia.

Complement C5-inhibiting therapy for the thrombotic microangiopathies: accumulating evidence, but not a panacea

Thrombotic microangiopathy (TMA), characterized by organ injury occurring consequent to severe endothelial damage, can manifest in a diverse range of diseases. In complement-mediated atypical haemolytic uraemic syndrome (aHUS) a primary defect in complement, such as a mutation or autoantibody leading to over activation of the alternative pathway, predisposes to the development of disease, usually following exposure to an environmental trigger. The elucidation of the pathogenesis of aHUS resulted in the successful introduction of the complement inhibitor eculizumab into clinical practice. In other TMAs, although complement activation may be seen, its role in the pathogenesis remains to be confirmed by an interventional trial. Although many case reports in TMAs other than complement-mediated aHUS hint at efficacy, publication bias, concurrent therapies and in some cases the self-limiting nature of disease make broader interpretation difficult. In this article, we will review the evidence for the role of complement inhibition in complement-mediated aHUS and other TMAs.

Cytopenias among ART-naive patients with advanced HIV disease on enrolment to care and treatment services at a tertiary hospital in Tanzania: A cross-sectional study

BACKGROUND

HIV/AIDS causes high morbidity and mortality through both immunosuppression and complications not directly related to immunosuppression. Haematological abnormalities, including various cytopenias, occur commonly in HIV through immune and non-immune pathways. Though these complications could potentially cause serious clinical implications, published literature on the magnitude of this problem and its associated factors in Tanzania is scarce. This study aimed at determining the prevalence and risk factors of HIV-associated cytopenias among ART-naive patients enrolling for care and treatment services at Bugando Care and Treatment Centre (CTC) in Mwanza, Tanzania.

METHODS

This was a cross-sectional clinic-based study done between March 2015 and February 2016, involving all antiretroviral therapy (ART)-naive adult HIV-positive patients enrolling for care and treatment services at Bugando CTC. Patients younger than 18 years and those with missing data were excluded. Data were analysed using Stata version 11 to determine the prevalence and risk factors of cytopenias.

RESULTS

A total of 1205 ART-naive patients were included. Median age was 41 years (interquartile range [IQR] 32 to 48). Most participants were female (n = 789; 65.6%), with a female-to-male ratio of 2:1. The median baseline CD4 count was 200 cells/µL (IQR 113 to 439). About half (49%) of the study participants had baseline CD4 counts less than 200 cells/µL. Anaemia, leucopenia, and thrombocytopenia were found in 704 (58.4%), 285 (23.6%), and 174 (14.4%) participants, respectively, and these were strongly associated with advanced HIV infection.

CONCLUSIONS

The magnitude of cytopenias is high among ART-naive HIV-positive adults, and cytopenias are more marked with advanced HIV infection. Early diagnosis of HIV and timely initiation of ART could potentially reduce the number of people living with advanced HIV disease and its associated complications, including the cytopenias investigated in this study. Patients with cytopenias should undergo thorough screening for tuberculosis, which is an important and treatable correlate of cytopenia, in addition to close follow-up for any potential negative outcomes.

Kidney Disease in Human Immunodeficiency Virus-seropositive Patients: Absence of Human Immunodeficiency Virus-associated Nephropathy was a Characteristic Feature

Human immunodeficiency virus (HIV) infection can cause a broad spectrum of renal diseases. However, there is paucity of Indian data on the patterns of renal lesions in HIV-seropositive patients. The aim of the present study was to delineate the spectrum of renal lesions in HIV/acquired immunodeficiency syndrome patients. In this prospective study, all HIV-positive patients of both genders aged >18 years were screened for renal disease. Patients with proteinuria of more than 1 g/24 h were subjected to renal biopsy. A total of 293 HIV-positive patients were screened; of these, 136 (46.4%) patients found to have renal involvement. Dipstick-positive proteinuria of 1+ or more was observed in 112 (38.2%) patients, and 16 (14.2%) patients had proteinuria of more than 1 g/24 h. Renal biopsy in 14 cases revealed glomerulonephritis (GN) in 12 (85.7%) (isolated GN in 4 [28.5%] and GN mixed with chronic TIN in 8 [57.1%]) patients. These include mesangioproliferative GN in 5 (35.7%), membranoproliferative GN in 2 (14.2%), focal segmental glomerulosclerosis in 2 (14.2%), diffuse proliferative GN in 2 (14.2%), and diabetic nephropathy in 1 (7.1%) patients. Chronic interstitial nephritis was noted in 10 (71.42%) (superimposed on GN in 8 [57.1%], isolated in 2 [14.2%]) patients. Granulomatous interstitial nephritis was seen in 3 (24.1%) cases. GN and chronic interstitial nephritis were noted in 85.7% and 71.42% of patients, respectively, mostly superimposed on each other. Mesangioproliferative GN was the most common glomerular lesion, but classical HIV-associated nephropathy was not observed.

Update on current management of chronic kidney disease in patients with HIV infection

The prevalence of HIV-associated chronic kidney disease (CKD) varies geographically and depends on the definition of CKD used, ranging from 4.7% to 38% globally. The incidence, however, has decreased with the use of effective combined antiretroviral therapy (cART). A wide variety of histological patterns are seen in HIV-associated kidney diseases that include glomerular and tubulointerstitial pathology. In resource-rich settings, there has been a plateau in the incidence of end-stage renal disease secondary to HIV-associated nephropathy (HIVAN). However, the prevalence of end-stage renal disease in HIV-positive individuals has risen, mainly due to increased longevity on cART. There is a disparity in the occurrence of HIVAN among HIV-positive individuals such that there is an 18- to 50-fold increased risk of developing kidney disease among HIV-positive individuals of African descent aged between 20 and 64 years and who have a poorer prognosis compared with their European descent counterparts, suggesting that genetic factors play a vital role. Other risk factors include male sex, low CD4 counts, and high viral load. Improvement in renal function has been observed after initiation of cART in patients with HIV-associated CKD. Treatment with an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker is recommended, when clinically indicated in patients with confirmed or suspected HIVAN or clinically significant albuminuria. Other standard management approaches for patients with CKD are recommended. These include addressing other cardiovascular risk factors (appropriate use of statins and aspirin, weight loss, cessation of smoking), avoidance of nephrotoxins, and management of serum bicarbonate and uric acid, anemia, calcium, and phosphate abnormalities. Early diagnosis of kidney disease by screening of HIV-positive individuals for the presence of kidney disease is critical for the optimal management of these patients. Screening for the presence of kidney disease upon detection of HIV infection and annually thereafter in high-risk populations is recommended.

Thrombotic Microangiopathy in the Setting of HIV Infection: A Case Report and Review of the Differential Diagnosis and Therapy

Before the modern era of HIV/AIDS therapeutics, which enabled a cascade of early recognition of infection, prompt initiation of effective antiretroviral therapies, and close follow-up, severe forms of microvascular clotting disorders known as thrombotic microangiopathies (TMAs) were frequent in the setting of advanced HIV disease. Their incidence was as high as 7% in the period 1984-1999, but fell dramatically, to <0.5%, by 2002. This profound change was predicated on one critical development: availability of new classes of anti-HIV drugs, enabling reduction and maintenance of HIV viral loads to undetectable levels. Another development in the period 1999-2002 related to TMA therapy: with recognition of autoantibodies against the von Willebrand factor cleaving protease ADAMTS13 as the etiology of most cases of one major form of TMA, thrombotic thrombocytopenic purpura, it permitted appropriate use of life-saving interventions based on plasma exchange and immune suppression. A more recent factor in TMA therapeutics was the 2011 approval by the US FDA and European EMA of eculizumab, a humanized monoclonal antibody against complement component C5, for the treatment of atypical hemolytic uremic syndrome, another major form of TMA. Despite these milestones, life- and organ-threatening TMAs still occur in untreated HIV disease and, to a much lesser extent, in those patients with suppressed viral loads. Confusion in terms of the differential diagnosis of these TMAs also impedes use of directed treatments. This report utilizes a case study of a young woman with advanced AIDS who presented with a severe TMA, characterized by coma and renal failure, to highlight the diagnostic and therapeutic challenges raised by complex hematologic conditions occurring in the setting of HIV.

Thrombotic microangiopathy as first manifestation of acute human immunodeficiency virus infection: a case report and review of the literature

Background

We present the case of a patient with acute human immunodeficiency virus infection and a thrombotic microangiopathy as the first clinical manifestation, a presentation that has not, to the best of our knowledge, been previously reported.

Case presentation

A 35-year-old Bolivian man presented with epistaxis and thrombocytopenia. We found microangiopathic anemia, lymphopenia, elevated lactate dehydrogenase, progressive acute renal failure, negative direct antiglobulin test, and normal activity of ADAMTS13. An human immunodeficiency virus ELISA test was negative, with an human immunodeficiency virus viral load of 10,000,000 RNA copies/mL. Antiretroviral therapy and three sessions of therapeutic plasma exchange were able to control thrombotic microangiopathy.

Conclusions

Hematologic manifestations of human immunodeficiency virus infection are frequent. However, the debut of acute human immunodeficiency virus infection with thrombotic microangiopathy is a rare event. A high index of suspicion and early treatment is required.

Thrombotic microangiopathy as an initial manifestation in HIV patients

Thrombotic microangiopathy (TMA) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, microvascular thrombosis, and various organ dysfunctions. TMA usually occurs in a more advanced stage of HIV disease. TMA as an initial presenting feature is rare. We here report a male patient who presented with oliguric renal failure. Investigations revealed anemia, thrombocytopenia, schistocytes in peripheral smear, and HIV-positive. Renal biopsy revealed TMA. He was treated with hemodialysis and started on highly active antiretroviral therapy.

Haematological manifestations of human immune deficiency virus infection

Early in the human immunodeficiency virus (HIV) epidemic, infected patients presented to medical attention with striking abnormalities in each of the major blood cell lineages. The reasons for these derangements remain complex and multifactorial. HIV infects multipotent haematopoietic progenitor cells and establish latent cellular reservoirs, disturbs the bone marrow microenvironment and also causes immune dysregulation. These events lead to cytokine imbalances and disruption of other factors required for normal haematopoiesis. Activation of the reticulo-endothelial system can also result in increased blood cell destruction. The deleterious effects of medications, including first and second generation anti-retroviral agents, on haematopoiesis were well documented in the early years of HIV care; in the current era of HIV-care, the advent of newer and less toxic anti-retroviral drugs have had a more beneficial impact on haematopoiesis. Due to impaired regulation of the immune system and potential side effects of one or more anti-retroviral agents, there is also an increase in coagulation abnormalities such as thromboembolism, and less frequently, acquired disorders of coagulation including thrombotic thrombocytopenic purpura, immune thrombocytopenic purpura and acquired inhibitors of coagulation. In this article we review the epidemiology and aetiology of select non-oncological haematological disorders commonly seen in people living with HIV-acquired immune deficiency syndrome.

Non-immune Hemolysis: Diagnostic Considerations

Non-immune hemolytic anemia (NIHA) is characterized by positive routine hemolytic tests but negative anti-human immunoglobulin (Coombs) test. Hereditary non-immune hemolysis includes disorders of erythrocytic enzymes, membrane, hemoglobin (qualitative and quantitative disorders), as well as the rare hereditary forms of thrombotic microangiopathies. Acquired NIHA includes paroxysmal nocturnal hemolysis (PNH), infections, drug and metal intoxications with as a target red blood cells or endothelium of capillaries, the rare acquired forms of thalassemia or erythrocytic membrane disorders, and hemolysis secondary to a dysfunctioning artificial (prosthetic) cardiac valve. Identification of the specific cause of NIHA is sometimes difficult and requires not only a good knowledge of this entity but mainly a qualified specialized hematologic laboratory. An algorithm to be used in every new patient consulting for NIHA is proposed in the last part of this article.

HIV-associated nephropathies: epidemiology, pathology, mechanisms and treatment

HIV is a highly adaptive, rapidly evolving virus, which is associated with renal diseases including collapsing glomerulopathy-the classic histomorphological form of HIV-associated nephropathy. Other nephropathies related to viral factors include HIV-immune-complex kidney disease and thrombotic microangiopathy. The distribution of HIV-associated kidney diseases has changed over time and continues to vary across geographic regions worldwide. The reasons for this diversity are complex and include a critical role of APOL1 variants and possibly other genetic factors, disparities in access to effective antiviral therapies, and likely other factors that we do not yet fully understand. The mechanisms responsible for HIVAN, including HIV infection of podocytes and tubular epithelial cells, the molecules responsible for HIV entry, and diverse mechanisms of cell injury, have been the focus of much study. Although combined antiretroviral therapy is effective at preventing and reversing HIVAN, focal segmental glomerulosclerosis, arterionephrosclerosis and diabetic nephropathy are increasingly common in individuals who have received such therapy for many years. These diseases are associated with metabolic syndrome, obesity and premature ageing. Future directions for HIV-related kidney disease will involve regular screening for drug nephrotoxicity and incipient renal disease, as well as further research into the mechanisms by which chronic inflammation can lead to glomerular disease.

Clinical practice guideline for the management of chronic kidney disease in patients infected with HIV: 2014 update by the HIV Medicine Association of the Infectious Diseases Society of America

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.

The impact of HIV-associated anaemia on the incidence of red blood cell transfusion: implications for blood services in HIV-endemic countries

Cytopaenias, especially anaemia, are common in the HIV-infected population. The causes of HIV related cytopaenias are multi-factorial and often overlapping. In addition, many of the drugs used in the management of HIV-positive individuals are myelosuppresive and can both cause and exacerbate anaemia. Even though blood and blood products are still the cornerstone in the management of severe cytopaenias, how HIV may affect blood utilisation is not well understood. The impact of HIV/AIDS on blood collections has been well documented. As the threat posed by HIV on the safety of the blood supply became clearer, South Africa introduced progressively more stringent donor selection criteria, based on the HIV risk profile of the donor cohort from which the blood collected. The implementation of new testing technology in 2008 which significantly improved the safety of the blood supply enabled the removal of what was perceived by many as a racially based donor risk model. However, this new technology had a significant and sustained impact on the cost of blood and blood products in South Africa. In contrast, it would appear little is known of how HIV influences the utilisation of blood and blood products. Considering the high prevalence of HIV among hospitalised patients and the significant risk for anaemia among this group, there would be an expectation that the transfusion requirements of an HIV-infected patient would be higher than that of an HIV-negative patient. However, very little published data is available on this topic which emphasises the need for further large-scale studies to evaluate the impact of HIV/AIDS on the utilisation of blood and blood products and how the large-scale roll-out of ARV programs may in future play a role in determining the country's blood needs.

[Thrombotic microangiopathy]

Thrombotic microangiopathy should be suspected every time the combination of microangiopathic hemolytic anemia without a coexisting cause, thrombocytopenia as well as renal and/or neurologic abnormalities occurs. The general term thrombotic microangiopathy includes different subtypes of the disease leading to abnormalities in multiple organ systems by endothelial injury and formation of platelet-rich thrombi in small vessels. The main types include thrombotic thrombocytopenic purpura in case of dominant neurologic abnormalities and the hemolytic uremic syndrome in case of acute kidney injury, respectively. Although these syndromes differ in their etiologies, clinical features, response to treatment, and prognosis, an early initiation of a direct therapeutic intervention frequently determines the clinical course of the patient. Irrespectively of the underlying etiology, plasma exchange is an essential component of acute therapeutic intervention while ongoing diagnostics are used to identify the definite treatment.

Predictors of HIV-associated nephropathy

Renal disease accounts for significant morbidity and mortality in patients with HIV-1 infection. HIV-associated nephropathy (HIVAN) is an important cause of end stage renal disease in this population. Although multiple genetic, clinical, and laboratory characteristics such as Apolipoproetin-1 genetic polymorphism, high viral load, low CD-4 count, nephrotic range proteinuria, and increased renal echogenicity on ultrasound are predictive of HIVAN, kidney biopsy remains the gold standard to make the definitive diagnosis. Current treatment options for HIVAN include initiation of combined active antiretroviral therapy, blockade of the renin-angiotensin system, and steroids. In patients with progression of HIVAN, renal transplant should be pursued as long as their systemic HIV infection is controlled.

Review: Viral infections and mechanisms of thrombosis and bleeding

Viral infections are associated with coagulation disorders. All aspects of the coagulation cascade, primary hemostasis, coagulation, and fibrinolysis, can be affected. As a consequence, thrombosis and disseminated intravascular coagulation, hemorrhage, or both, may occur. Investigation of coagulation disorders as a consequence of different viral infections have not been performed uniformly. Common pathways are therefore not fully elucidated. In many severe viral infections there is no treatment other than supportive measures. A better understanding of the pathophysiology behind the association of viral infections and coagulation disorders is crucial for developing therapeutic strategies. This is of special importance in case of severe complications, such as those seen in hemorrhagic viral infections, the incidence of which is increasing worldwide. To date, only a few promising targets have been discovered, meaning the implementation in a clinical context is still hampered. This review discusses non‐hemorrhagic and hemorrhagic viruses for which sufficient data on the association with hemostasis and related clinical features is available. This will enable clinicians to interpret research data and place them into a perspective. J. Med. Virol. 84:1680–1696, 2012. © 2012 Wiley Periodicals, Inc.

Kidney Disease in HIV-Infected Persons

Kidney disease is more prevalent among persons living with HIV, and may arise from a combination of comorbidities, co-infections, and medication-associated toxicities. Additional effects of HIV-1 viral replication, immunodeficiency and genetic factors also contribute to kidney disease. As is true in the general population, persons of African descent exhibit a disproportionate risk for severe kidney disease. Antiretroviral therapy (ART) modifies the natural history of HIV-associated nephropathy (HIVAN), and renal benefits of ART may not be limited to persons with HIVAN. Robust associations between proteinuria and cardiovascular disease imply that common mechanisms of vascular endothelial dysfunction may contribute to both processes.

Viral-associated thrombotic microangiopathies

Thrombotic microangiopathies encompass a group of disorders characterized by microangiopathic hemolytic anemia, thrombocytopenia associated with hyaline thrombi (comprised primarily of platelet aggregates in the microcirculation), and varying degrees of end-organ failure. Many primary (genetic) and secondary etiological predisposing factors have been described-namely pregnancy, autoimmune disorders, cancer, drugs and antineoplastic therapy, bone marrow transplantation/solid organ transplantation, and infections. In the setting of infectious diseases, the association with Shiga or Shiga-like exotoxin of Escherichia coli 0157:h7 or Shigella dysenteriae type 1-induced typical hemolytic uremic syndrome is well known. Recently however, an increasing body of evidence suggests that viruses may also play an important role as trigger factors in the pathogenesis of thrombotic microangiopathies. This is a comprehensive review focusing on the current understanding of viral associated/induced endothelial stimulation and damage that ultimately leads to the development of this life-threatening multisystemic disorder.

Hemolytic uremic syndrome: new developments in pathogenesis and treatment

Hemolytic uremic syndrome is defined by the characteristic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. In children, most cases of HUS are caused by Shiga-toxin-producing bacteria, especially Escherichia coli O157:H7. Common vehicles of transmission include ground beef, unpasteurized milk, and municipal or swimming water. Shiga-toxin-associated HUS is a main cause of acute renal failure in young children. Management remains supportive as there is at present no specific therapy to ameliorate the prognosis. Immediate outcome is most often favourable but long-term renal sequelae are frequent due to nephron loss. Atypical HUS represents 5% of cases. In the past 15 years, mutations in complement regulators of the alternative pathway have been identified in almost 60% of cases, leading to excessive complement activation. The disease has a relapsing course and more than half of the patients either die or progress to end-stage renal failure. Recurrence after renal transplantation is frequent.

Thrombotic microangiopathy in haematopoietic cell transplantation: an update

Allogeneic hematopoietic cell transplantation (HCT) represents a vital procedure for patients with various hematologic conditions. Despite advances in the field, HCT carries significant morbidity and mortality. A rare but potentially devastating complication is transplantation-associated thrombotic microangiopathy (TA-TMA). In contrast to idiopathic TTP, whose etiology is attributed to deficient activity of ADAMTS13, (a member of the A Disintegrin And Metalloprotease with Thrombospondin 1 repeats family of metalloproteases), patients with TA-TMA have > 5% ADAMTS13 activity. Pathophysiologic mechanisms associated with TA-TMA, include loss of endothelial cell integrity induced by intensive conditioning regimens, immunosuppressive therapy, irradiation, infections and graft-versus-host (GVHD) disease. The reported incidence of TA-TMA ranges from 0.5% to 75%, reflecting the difficulty of accurate diagnosis in these patients. Two different groups have proposed consensus definitions for TA-TMA, yet they fail to distinguish the primary syndrome from secondary causes such as infections or medication exposure. Despite treatment, mortality rate in TA-TMA ranges between 60% to 90%. The treatment strategies for TA-TMA remain challenging. Calcineurin inhibitors should be discontinued and replaced with alternative immunosuppressive agents. Daclizumab, a humanized monoclonal anti-CD25 antibody, has shown promising results in the treatment of TA-TMA. Rituximab or the addition of defibrotide, have been reported to induce remission in this patient population. In general, plasma exchange is not recommended.

Variant-specific quantification of factor H in plasma identifies null alleles associated with atypical hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is associated with complement alternative pathway defects in over half the cases. Point mutations that affect complement surface regulation are common in factor H (CFH); however, sometimes individuals have null mutations in heterozygosis. The latter are difficult to identify, although a consistently low plasma factor H (fH) concentration is suggestive; definitive proof requires demonstration that the mutant sequence is not expressed in vitro. Here, novel reagents and assays that distinguish and individually quantify the common factor H-Y402H polymorphic variants were used to identify alleles of the CFH gene, resulting in low or null expression of full-length fH and also normal or increased expression of the alternative splice product factor H-like-1 (FHL-1). Our assay identified three Y402H heterozygotes with low or absent fH-H402 but normal or increased FHL-1-H402 levels in a cohort of affected patients. Novel mutations explained the null phenotype in two cases, which was confirmed by family studies in one. In the third case, family studies showed that a known mutation was present on the Y allele. The cause of reduced expression of the H allele was not found, although the data suggested altered splicing. In each family, inheritance of low expression or null alleles for fH strongly associated with aHUS. Thus, our assays provide a rapid means to identify fH expression defects without resorting to gene sequencing or expression analysis.