Systemic infections mimicking thrombotic thrombocytopenic purpura

Molecular Mimicry: An Uncommon Occurrence of Vitamin B12 Deficiency Imitating Thrombotic Thrombocytopenic Purpura in an African American Male

Thrombotic thrombocytopenic purpura (TTP) and vitamin B12 deficiency can share similar symptoms but require different treatment approaches. TTP is a blood disorder with a high mortality rate requiring immediate plasmapheresis treatment. On the other hand, vitamin B12 deficiency usually presents with anemia, low platelet counts, jaundice, and signs of disrupted red blood cell breakdown, resembling a condition called microangiopathic hemolytic anemia. Vitamin B12 deficiency can sometimes lead to or mimic pseudo-thrombotic microangiopathy (pseudo-TMA), a rare occurrence. Pseudo-TMA manifests as microangiopathic hemolytic anemia and thrombocytopenia and is characterized by schistocytes in a peripheral blood smear. Differentiating TTP cases from pseudo-TMA cases is essential and should be done promptly. The etiology, treatments, and prognosis of these two conditions differ and can be fatal if not identified and managed. We present a case that emphasizes the need for familiarity with TTP-like conditions, the use of ADAMTS13 as a diagnostic tool, prompt and accurate treatment decision-making, the complexities of therapeutic plasma exchange, and the importance of excluding an enzyme inhibitor or mutator as the cause of TTP or TTP-like cases. Lack of knowledge can lead to erroneous diagnoses, resulting in unnecessary treatments or delayed life-saving interventions.

Challenges in the diagnosis of thrombotic thrombocytopenic purpura

INTRODUCTION

Immune-mediated TTP (iTTP) is a rare condition without pathognomonic signs and symptoms. For this reason, the diagnosis of iTTP may be delayed or even missed, with potentially catastrophic consequences.

AREAS COVERED

The authors performed an extensive literature review on the diagnosis of iTTP and its challenges combined with their own experience in a referral center for patients with iTTP.

EXPERT OPINION

Although a definitive diagnosis of iTTP depends on the ADAMTS13 activity result, timely testing is rarely available at many centers to which patients present. If less complex tests were to become available, they would decrease the chances of late and/or missed diagnoses of iTTP throughout the world. While clinical scores to estimate the likelihood of iTTP exist, they are not well known, and can be misleading if used in the wrong context. Furthermore, the three scoring systems (PLASMIC, Bentley, and French) only moderately correlate with each other, which further complicates the landscape. The existence of these scores and how they should be used in practice is but one opportunity that can be seized through more robust programs to educate nonspecialist clinicians on how to recognize and treat patients with iTTP.

HUS and TTP: traversing the disease and the age spectrum

Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenia purpura (TTP) are rare diseases sharing a common pathological feature, thrombotic microangiopathy (TMA). TMA is characterized by microvascular thrombosis with consequent thrombocytopenia, microangiopathic hemolytic anemia and/or multiorgan dysfunction. In the past, the distinction between HUS and TTP was predominantly based on clinical grounds. However, clinical presentation of the two syndromes often overlaps and, the differential diagnosis is broad. Identification of underlying pathogenic mechanisms has enabled the classification of these syndromes on a molecular basis: typical HUS caused by Shiga toxin-producing Escherichia coli (STEC-HUS); atypical HUS or complement-mediated TMA (aHUS/CM-TMA) associated with genetic or acquired defects leading to dysregulation of the alternative pathway (AP) of complement; and TTP that results from a severe deficiency of the von Willebrand Factor (VWF)-cleaving protease, ADAMTS13. The etiology of TMA differs between pediatric and adult patients. Childhood TMA is chiefly caused by STEC-HUS, followed by CM-TMA and pneumococcal HUS (Sp-HUS). Rare conditions such as congenital TTP (cTTP), vitamin B12 metabolism defects, and coagulation disorders (diacylglycerol epsilon mutation) present as TMA chiefly in children under 2 years of age. In contrast secondary causes and acquired ADAMT13 deficiency are more common in adults. In adults, compared to children, diagnostic delays are more frequent due to the wide range of differential diagnoses. In this review we focus on the three major forms of TMA, STEC-HUS, aHUS and TTP, outlining the clinical presentation, diagnosis and management of the affected patients, to help highlight the salient features and the differences between adult and pediatric patients which are relevant for management.

Stillbirth and fulminant postpartum haemolysis: COVID-19 or leptospirosis or both?

We report the case of a female patient with a SARS-CoV-2 infection first diagnosed at 32 2/7 weeks of gestation, resulting in stillbirth at 33 5/7 weeks of gestation. Post partum the patient presented with severe and persistent haemolysis, mild thrombocytopaenia, renal insufficiency and proteinuria as well as elevated liver enzymes and jaundice. Further investigations revealed a positive IgM for Leptospira interrogans and proof of infection by PCR in the urine. The patient was treated with penicillin for 7 days and received a total of 23 units of red blood cells within 11 days. Haemolysis diminished over time and haemoglobin, proteinuria and transaminases normalised within 23 days after delivery. We suppose an acute leptospirosis as underlying cause for the haemolysis, mimicking pregnancy-associated thrombotic microangiopathy. Whether stillbirth was related to leptospirosis or SARS-CoV-2 infection remains unclear.

Vitamin B12 deficiency presenting with a pancytopenia in pregnancy

Vitamin B12 deficiency is a significant public health problem globally. Although it is a well-known cause of macrocytic anaemia and in advanced cases, pancytopenia, there remains a relative paucity of cases reported in pregnancy. It is associated with an increased risk of pregnancy complications and adverse birth outcomes such as neural tube defects, preterm birth, low birth weight, neurological sequelae and intrauterine death. It has a predilection for individuals aged >60 years. It has been implicated in a spectrum of neuropsychiatric disorders and it may also exert indirect cardiovascular effects. Severe vitamin B12 deficiency may present with haematological abnormalities that mimic thrombotic microangiopathy such as HELLP syndrome (haemolysis, elevated liver enzymes and low platelets) or it may present as pseudothrombotic microangiopathy (Moschcowitz syndrome) characterised by anaemia, thrombocytopenia and schistocytosis. It can also closely mimic thrombotic thrombocytopenia purpura, hence posing a diagnostic challenge to the unwary physician. Serological measurement of vitamin B12 levels confirms the diagnosis. Oral supplementation with vitamin B12 remains a safe and effective treatment. The authors describe the case of a multiparous woman in her late 20s presenting with a plethora of non-specific symptoms at 29+5 weeks' gestation. Her haemoglobin was 45 g/L, platelets 32×109/L, vitamin B12 <150 ng/L and serum folate <2 µg/L. She was not a vegetarian, but her diet lacked nutrition. Following parenteral B12 supplementation, her haematological parameters improved. The pregnancy was carried to term. Due to the plethora of non-specific symptoms, the diagnosis can be challenging to establish. Adverse maternal or fetal outcomes may occur. Folic acid supplementation may mask an occult vitamin B12 deficiency and further exacerbate or initiate neurological disease.

Coagulation Disorders in Sepsis and COVID-19-Two Sides of the Same Coin? A Review of Inflammation-Coagulation Crosstalk in Bacterial Sepsis and COVID-19

Sepsis is a major cause of morbidity and mortality worldwide. Sepsis-associated coagulation disorders are involved in the pathogenesis of multiorgan failure and lead to a subsequently worsening prognosis. Alongside the global impact of the COVID-19 pandemic, a great number of research papers have focused on SARS-CoV-2 pathogenesis and treatment. Significant progress has been made in this regard and coagulation disturbances were once again found to underlie some of the most serious adverse outcomes of SARS-CoV-2 infection, such as acute lung injury and multiorgan dysfunction. In the attempt of untangling the mechanisms behind COVID-19-associated coagulopathy (CAC), a series of similarities with sepsis-induced coagulopathy (SIC) became apparent. Whether they are, in fact, the same disease has not been established yet. The clinical picture of CAC shows the unique feature of an initial phase of intravascular coagulation confined to the respiratory system. Only later on, patients can develop a clinically significant form of systemic coagulopathy, possibly with a consumptive pattern, but, unlike SIC, it is not a key feature. Deepening our understanding of CAC pathogenesis has to remain a major goal for the research community, in order to design and validate accurate definitions and classification criteria.

THROMBOTIC MICROANGIOPATHY: DIAGNOSTIC CHALLENGES IN THE PRIMARY MULTIPLE NEOPLASM INVOLVEMENT WITH PREVALENT METASTASIS WITH GRANULOMATOSIS INFLAMMATORY FOCUSES

Patient, who died during the hospital stay, had hemoblastosis and syphilis in the reported medical history. While the patient was examined doctors suspected the presence of malignancy with unknown primary localization with multiple metastatic injuries with clinical and laboratory TTP signs (hemorrhagic syndrome, thrombocytopenia, shystocytosis, and non-immune hemolytic anemia). Despite treatment, the general patient's condition progressively worsens with increasing multiple organ decompensation signs. In the final stage of the disease course, after heart arrest and the appearance of clinical death signs CPR measures were performed according to complete guidance, but CRP had no positive effect. Biological death was constated. Considering the criteria of the diagnostic clinical and laboratory dyad (thrombocytopenia and microangiopathic hemolytic anemia), the data of the patholog¬ical examination (multiple metastatic lesions, inflammatory process, tumor intoxication, thrombosis), the combination of manifestations of chronic myeloid leukemia, prostate cancer with multiple metastases, tertiary syphilis served as a condition for the initiation of TTP, which was of decisive importance in the development of the patient's death.

Case report of Salmonella derby septicemia complicated with co-occurrence of disseminated intravascular coagulation and thrombotic microangiopathy

BACKGROUND

Both disseminated intravascular coagulation and thrombotic microangiopathy are complications of sepsis as Salmonella septicemia, respectively. They are related and have similar clinical characteristics as thrombopenia and organ dysfunctions. They rarely co-occur in some specific cases, which requires a clear distinction.

CASE PRESENTATION

A 22-year-old woman had just undergone intracranial surgery and suffered from Salmonella derby septicemia with multiorgan involvement in the hospital. Laboratory workup demonstrated coagulation disorder, hemolytic anemia, thrombocytopenia, and acute kidney injury, leading to the co-occurrence of disseminated intravascular coagulation and secondary thrombotic microangiopathy. She received antibiotics, plasma exchange therapy, dialysis, mechanical ventilation, fluids, and vasopressors and gained full recovery without complications.

CONCLUSION

Disseminated intravascular coagulation and secondary thrombotic microangiopathy can co-occur in Salmonella derby septicemia. They should be treated cautiously in diagnosis and differential diagnosis. Thrombotic microangiopathy should not be missed just because of the diagnosis of disseminated intravascular coagulation. Proper and timely identification of thrombotic microangiopathy with a diagnostic algorithm is essential for appropriate treatment and better outcomes.

COVID-19 vaccine (mRNA BNT162b2) and COVID-19 infection-induced thrombotic thrombocytopenic purpura in adolescents

The mRNA COVID-19 vaccine and COVID-19 infection caused by the SARS-CoV-2 virus may be immunologic triggers for the development of thrombotic thrombocytopenic purpura (TTP). There is not yet literature that discusses TTP induced by COVID-19 vaccination or infection in pediatric or adolescent patients. We describe three adolescents presenting with TTP (both de novo and relapsed disease) following administration of the Pfizer COVID-19 vaccine or after COVID-19 infection. Our observations demonstrate that the Pfizer-BioNTech mRNA vaccine and COVID-19 infection can act as triggers for the development/relapse of both congenital and acquired TTP.

Clinical features and outcomes of four atypical hemolytic uremic syndrome cases at a single institution in Miyazaki Prefecture from 2015 to 2019

Background

Although atypical hemolytic uremic syndrome (aHUS) is a life-threatening clinical entity that was characterized by thrombotic microangiopathy (TMA) with the activation of the complement system and the efficient treatment of eculizumab, the clinical features of aHUS have been unclear because of the rare incidence.

Case presentation

We retrospectively analyzed 4 aHUS cases at a single institution during 2015–2019. Here, we presented 4 aHUS cases with renal transplantation (one case), influenza/acute interstitial pneumonia/disseminated intravascular coagulation (two cases), and severe fever with thrombocytopenia syndrome (one case), respectively. Initial clinical symptoms were microangiopathic hemolytic anemia (four cases), renal dysfunction (four cases), thrombocytopenia (four cases), and pulmonary hemorrhage (three cases) consisted with TMA features. Subsequent further examinations ruled out thrombotic thrombocytopenic purpura, Shiga toxin-producing E.coli-induced hemolytic uremic syndrome, and secondary TMA. Taken these findings together, we made the clinical diagnosis of aHUS. Furthermore, all cases also presented the high levels of plasma soluble C5b-9 (871.1 ng/ml, 1144.3 ng/ml, 929.2 ng/ml, and 337.5 ng/ml), suggesting persistent activation of complementary system. Regarding the treatment, plasma exchange (PE) (four cases) and eculizumab (two cases) therapy were administered for aHUS cases. Consequently, case 2 and case 4 were still alive with 768 days and 235 days, respectively. The other two cases were dead at 34 days and 13 days, respectively. Finally, although the previous reported genetic pathogenetic mutations were not detected in our cases, multiple genetic variants of complement factors were detected as CFH (H402Y, E936D), and THBD (A473V) in case 1, CFH (V62I, H402Y, V837I) in case 2, and CFH (H402Y, E 936D) and THBD (A473V) in case 3, CFH (V62I, H402Y, E936D) and THBD (473V) in case 4, respectively.

Conclusions

Because of still high mortality in our study, an urgent diagnosis of aHUS and subsequent immediate treatment including PE and eculizumab should be essential in clinical practice. Furthermore, the multiple genetic variants and the triggers may be related to one of the pathogenesis of aHUS. Thus, we assume that such a case-oriented study would be highly useful to the physicians who directly care for aHUS cases in clinical practice.

Clinicopathologic features among different viral epidemic outbreaks involving the skin

The current coronavirus disease 2019 pandemic has exceeded any epidemiologic prevision, but increasing information suggests some analogies with the major viral outbreaks in the last century, and a general warning has been issued on the possibility that coinfections can make the differential diagnosis and treatment difficult, especially in tropical countries. Some reports have noted that the presence of high dengue antibodies can give a false-negative result when testing for severe acute respiratory syndrome coronavirus 2. Mucocutaneous manifestations are very frequent, with an apparent overlap among different pathogens. However, strong clinicopathologic correlation might provide some clues to address differentials. Waiting for laboratory and instrumental results, the timing and distribution of skin lesions is often pathognomonic. Histopathologic findings characterize certain reaction patterns and provide insights on pathogenetic mechanisms. Unfortunately, skin assessment, especially invasive examinations such as biopsy, takes a back seat in severely ill patients. A literature retrieval was performed to collect information from other epidemics to counteract what has become the most frightening disease of our time.

Emerging Concepts in Immune Thrombotic Thrombocytopenic Purpura

Immune thrombotic thrombocytopenic purpura (iTTP) is an autoimmune disorder of which the etiology is not fully understood. Autoantibodies targeting ADAMTS13 in iTTP patients have extensively been studied, the immunological mechanisms leading to the breach of tolerance remain to be uncovered. This review addresses the current knowledge on genetic factors associated with the development of iTTP and the interplay between the patient’s immune system and environmental factors in the induction of autoimmunity against ADAMTS13. HLA-DRB1*11 has been identified as a risk factor for iTTP in the Caucasian population. Interestingly, HLA-DRB1*08:03 was recently identified as a risk factor in the Japanese population. Combined in vitro and in silico MHC class II peptide presentation approaches suggest that an ADAMTS13-derived peptide may bind to both HLA-DRB1*11 and HLA-DRB1*08:03 through different anchor-residues. It is apparent that iTTP is associated with the presence of infectious microorganisms, viruses being the most widely associated with development of iTTP. Infections may potentially lead to loss of tolerance resulting in the shift from immune homeostasis to autoimmunity. In the model we propose in this review, infections disrupt the epithelial barriers in the gut or lung, promoting exposure of antigen presenting cells in the mucosa-associated lymphoid tissue to the microorganisms. This may result in breach of tolerance through the presentation of microorganism-derived peptides that are homologous to ADAMTS13 on risk alleles for iTTP.

Signaling pathways and intervention therapies in sepsis

Sepsis is defined as life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection. Over decades, advanced understanding of host-microorganism interaction has gradually unmasked the genuine nature of sepsis, guiding toward new definition and novel therapeutic approaches. Diverse clinical manifestations and outcomes among infectious patients have suggested the heterogeneity of immunopathology, while systemic inflammatory responses and deteriorating organ function observed in critically ill patients imply the extensively hyperactivated cascades by the host defense system. From focusing on microorganism pathogenicity, research interests have turned toward the molecular basis of host responses. Though progress has been made regarding recognition and management of clinical sepsis, incidence and mortality rate remain high. Furthermore, clinical trials of therapeutics have failed to obtain promising results. As far as we know, there was no systematic review addressing sepsis-related molecular signaling pathways and intervention therapy in literature. Increasing studies have succeeded to confirm novel functions of involved signaling pathways and comment on efficacy of intervention therapies amid sepsis. However, few of these studies attempt to elucidate the underlining mechanism in progression of sepsis, while other failed to integrate preliminary findings and describe in a broader view. This review focuses on the important signaling pathways, potential molecular mechanism, and pathway-associated therapy in sepsis. Host-derived molecules interacting with activated cells possess pivotal role for sepsis pathogenesis by dynamic regulation of signaling pathways. Cross-talk and functions of these molecules are also discussed in detail. Lastly, potential novel therapeutic strategies precisely targeting on signaling pathways and molecules are mentioned.

Clinicopathologic features between different viral epidemic outbreaks involving the skin

The current coronavirus disease 2019 pandemic has exceeded any epidemiologic prevision, but increasing information suggests some analogies with the major viral outbreaks of the last century. A general warning has been issued on the possibility that coinfections can make differential diagnosis and treatment difficult, especially in tropical countries. Some reports have pointed out that the presence of high Dengue antibodies can give a false-negative result for severe acute respiratory syndrome coronavirus 2. Mucocutaneous manifestations are very frequent, with an apparent overlap among different pathogens. A strong clinicopathologic correlation, however, may provide some clues to address the differential. Waiting for laboratory and instrumental results, the timing and distribution of skin lesions is often pathognomonic. Histopathologic findings characterize certain reaction patterns and provide insights on pathogenetic mechanisms. Unfortunately, skin assessments, especially invasive exams such as biopsy, are less important in severely ill patients. A literature review was performed to collect information from other epidemics to counteract what has become the most frightening disease of our time.

Complement Activation in Human Sepsis is Related to Sepsis-Induced Disseminated Intravascular Coagulation

INTRODUCTION

In human sepsis, little is known about the relationships between complement activation and the clinical characteristics of sepsis, including disseminated intravascular coagulation (DIC), interventions, and prognosis.

PATIENTS AND METHODS

Adult patients with sepsis admitted from November 2016 to December 2018 were included. We used the plasma levels of soluble C5b-9 (SC5b-9) as a marker of complement activation. We compared the clinical characteristics and complement components between patients with and without DIC. We also compared the clinical characteristics and each DIC parameter across quartile groups for the SC5b-9 value.

RESULTS

Forty-nine sepsis patients were eligible. Thirty-four patients developed DIC, and eight patients died. The median (interquartile range) SC5b-9 value was 342 (261-501) ng/mL. Compared with patients without DIC, patients with DIC showed lower C3 levels (mean, 95.7 vs. 70.4 mg/dL, P < 0.01) and higher SC5b-9 levels (median, 287 vs. 400 ng/mL, P = 0.01). Patients were stratified by SC5b-9 quartile (ng/mL: low: < 260, moderate: 260-342, high: 343-501, highest: > 501). The mean Sequential Organ Failure Assessment score varied across these groups (P = 0.02). In the high and highest groups, many more patients received vasopressors and developed DIC. In the highest group, the coagulation parameters were severe, and thrombocytopenia was prolonged. In-hospital mortality tended to be high (33%) in the highest group.

CONCLUSIONS

The degree of complement activation is related to DIC, severity, intensive interventions, and mortality. Further studies are needed to confirm the usefulness of SC5b-9 for stratifying sepsis patients.

Thrombotic microangiopathies assessment: mind the complement

When faced with microangiopathic haemolytic anaemia, thrombocytopenia and organ dysfunction, clinicians should suspect thrombotic microangiopathy (TMA). The endothelial damage that leads to this histological lesion can be triggered by several conditions or diseases, hindering an early diagnosis and aetiological treatment. However, due to systemic involvement in TMA and its low incidence, an accurate early diagnosis is often troublesome. In the last few decades, major improvements have been made in the pathophysiological knowledge of TMAs such as thrombotic thrombocytopenic purpura [TTP, caused by ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin Type 1 motif, member 13) deficiency] and atypical haemolytic uraemic syndrome (aHUS, associated with dysregulation of the alternative complement pathway), together with enhancements in patient management due to new diagnostic tools and treatments. However, diagnosis of aHUS requires the exclusion of all the other entities that can cause TMA, delaying the introduction of terminal complement blockers, which have shown high efficacy in haemolysis control and especially in avoiding organ damage if used early. Importantly, there is increasing evidence that other forms of TMA could present overactivation of the complement system, worsening their clinical progression. This review addresses the diagnostic and therapeutic approach when there is clinical suspicion of TMA, emphasizing complement evaluation as a potential tool for the inclusive diagnosis of aHUS, as well as for the improvement of current knowledge of its pathophysiological involvement in other TMAs. The development of both new complement activation biomarkers and inhibitory treatments will probably improve the management of TMA patients in the near future, reducing response times and improving patient outcomes.

Leptospirosis Presenting with Features of Thrombotic Microangiopathy

Leptospirosis is an exceptionally rare infectious disease in the Republic of Ireland. Leptospirosis can present with or mimic thrombotic microangiopathies (TTP/HUS). A 48-year-old male presented to a peripheral hospital with a short history of diarrhoea, anaemia, hyperbilirubinemia, raised lactate dehydrogenase, thrombocytopenia, and severe acute kidney injury and was transferred to our tertiary care kidney centre. A form of acute thrombotic microangiopathy (TMA) was suspected. However, no schistocytes were seen on the blood film, and the reticulocyte count was depressed. A kidney biopsy was performed before initiating any potential treatment which revealed acute interstitial nephritis (AIN). Leptospirosis was considered and subsequently serologically confirmed. The patient was managed with antimicrobials and supportive therapy. Acute kidney injury is common in leptospirosis and is often due to AIN. Initial presentation can mimic TMA; however, a differential diagnosis of leptospirosis should be considered even in nonendemic areas due to re-emergence of the disease.

Modifying ADAMTS13 to modulate binding of pathogenic autoantibodies of patients with acquired thrombotic thrombocytopenic purpura

Antibodies that develop in patients with immune thrombotic thrombocytopenic purpura (iTTP) commonly target the spacer epitope R568/F592/R660/Y661/Y665 (RFRYY). In this study we present a detailed contribution of each residue in this epitope for autoantibody binding. Different panels of mutations were introduced here to create a large collection of full-length ADAMTS13 variants comprising conservative (Y←→F), semi-conservative (Y/F→L), non-conservative (Y/F→N) or alanine (Y/F/R→A) substitutions. Previously reported Gain-of-Function (GoF, KYKFF) and truncated 'MDTCS' variants were also included. Sera of 18 patients were screened against all variants. Conservative mutations of the aromatic residues did not reduce the binding of autoantibodies. Moderate resistance was achieved by replacing R568 and R660 by lysines or alanines. Semi-conservative mutations of aromatic residues show a moderate effectiveness in autoantibody resistance. Non-conservative asparagine or alanine mutations of aromatic residues are the most effective. In the mixtures of autoantibodies from the majority (89%) of patients screened, autoantibodies targeting the spacer RFRYY epitope have preponderance compared to other epitopes. Reductions in ADAMTS13 proteolytic activity were observed for all full-length mutant variants, in varying degrees. The greatest activity reductions were observed in the most autoantibody-resistant variants (15-35% residual activity in FRETS-VWF73). Among these, a triple-alanine mutant RARAA showed activity in a VWF multimer assay. This study shows that non-conservative and alanine modifications of residues within the exosite-3 spacer RFRYY epitope in full-length ADAMTS13 resist the binding of autoantibodies from iTTP patients, while retaining residual proteolytic activity. Our study provides a framework for the design of autoantibody-resistant ADAMTS13 variants for further therapeutic development.

Disseminated intravascular coagulation: new identity as endotheliopathy-associated vascular microthrombotic disease based on in vivo hemostasis and endothelial molecular pathogenesis

Disseminated intravascular coagulation (DIC) can be correctly redefined as disseminated intravascular microthrombosis based on "two-path unifying theory" of in vivo hemostasis. "DIC" is a form of vascular microthrombotic disease characterized by "microthrombi" composed of platelets and unusually large von Willebrand factor multimers (ULVWF). Microthrombotic disease includes not only "DIC", but also microthrombosis occurring in thrombotic thrombocytopenic purpura (TTP), TTP-like syndrome, and focal, multifocal and localized microthrombosis. Being a hemostatic disease, microthrombotic disease occurs as a result of lone activation of ULVWF path via partial in vivo hemostasis. In endothelial injury associated with critical illnesses such as sepsis, the vascular damage is limited to the endothelial cell and activates ULVWF path. In contrast, in intravascular traumatic injury, the local damage may extend from the endothelial cell to subendothelial tissue and sometimes beyond, and activates both ULVWF and tissue factor (TF) paths. When endotheliopathy triggers exocytosis of ULVWF and recruits platelets, ULVWF path is activated and promotes microthrombogenesis to produce microthrombi composed of microthrombi strings, but when localized vascular damage causes endothelial and subendothelial tissue damage, both ULVWF and TF paths are activated and promote macrothrombogenesis to produce macrothrombus made of complete "blood clots". Currently, "DIC" concept is ascribed to activated TF path leading to fibrin clots. Instead, it should be correctly redefined as microthrombosis caused by activation of ULVWF path, leading to endotheliopathy-associated microthrombosis. The correct term for acute "DIC" is disseminated microthrombosis-associated hepatic coagulopathy, and that for chronic "DIC" is disseminated microthrombosis without hepatic coagulopathy. TTP-like syndrome is hematologic phenotype of endotheliopathy-associated microthrombosis. This correct concept of "DIC" is identified from novel theory of "in vivo hemostasis", which now can solve every mystery associated with "DIC" and other associated thrombotic disorders. Thus, sepsis-associated coagulopathy is not "DIC", but is endotheliopathy-associated vascular microthrombotic disease.

Assessment and Monitoring of Patients with Immune-Mediated Thrombotic Thrombocytopenic Purpura (iTTP): Strategies to Improve Outcomes

Background

Acquired or immune-mediated TTP (iTTP) is a life-threatening thrombotic microangiopathy, characterized by the presence of microangiopathic hemolytic anemia and severe thrombocytopenia, and a variable degree of ischemic organ damage, related to a severe deficiency of ADAMTS13, which is a serine metalloprotease necessary for cleavage of large vWF multimers. There has been a dramatic decrease in mortality rates with the recognition of the pathophysiology of iTTP over the years. Although therapeutic plasma exchange (TPE) together with corticosteroids are the backbone of the upfront treatment of patients with iTTP with successful outcomes, patients may remain refractory and/or relapse following an initial response to this treatment.

Methods

We performed a review regarding the pathogenesis, diagnosis, treatment strategies, monitoring, and prognosis of iTTP.

Results

There are several new treatment strategies, which can be used among these patients, helping in improving outcomes of iTTP. Rituximab has been shown to be a safe and effective adjunct to TPE, especially in patients with refractory and/or relapse as well as it is increasingly used preemptively to prevent exacerbation or recurrence. Recently, caplacizumab, a nanobody targeting vWF, was approved as an addition to the current regimen of TPE and immunomodulation for patients of iTTP.

Conclusion

Specific predictors of relapse in patients in remission can be relevant for an optimal patient management. Different models including ADAMTS13 biomarkers can provide a new screening strategy to identify patients who may predict outcomes and the risk of relapse, benefit from preemptive therapy prior to relapse.

Clinical presentation and management of acquired thrombotic thrombocytopenic purpura: A case series of 55 patients

The aim of this study was to explore the clinical characteristics and treatment of acquired thrombotic thrombocytopenic purpura (TTP). The clinical manifestations, laboratory findings, differential diagnoses, therapeutic methods, and prognosis of 55 patients with acquired TTP were retrospectively analyzed. Among the 55 TTP patients, 17 were males and 38 were females, with a mean age of 40 ± 15 years. Twenty-one patients had the Triad syndrome, which included neurological syndromes, microangiopathic hemolytic anemia, and thrombocytopenia. Twenty-three patients had the Quinary syndrome, which included fever, microangiopathic hemolytic anemia, thrombocytopenia, renal insufficiency, and neurological symptoms. Twenty-eight patients received the measurement for a disintegrin and metalloprotease with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity and 23 patients had <10% of the normal range. ADAMTS13 inhibitor was tested in 20 patients and was positive in 18 patients. Both ADAMTS13 activity and ADAMTS13 inhibitor were examined in 20 patients and 90% of the patients showed double positive results. The treatment methods included plasma exchange, glucocorticoids, rituximab, immunosuppressants, and intravenous immunoglobulin. Thirty-three patients survived, and 22 patients died. Plasma exchange improved the remission rate from 16.7% to 65.3% (P = .022). The combined immunosuppressive therapy based on plasma exchange and glucocorticoids raised the remission rate from 43.8% to 75.8%. Most of acquired TTP patients had the Triad syndrome or the Quinary syndrome. A high proportion of TTP patients had ADAMTS13 activity reduction and ADAMTS13 inhibitor positivity. Plasma exchange and immunosuppressive therapy may improve the prognosis of this disease.

Thrombotic thrombocytopenic purpura: A case report and review of literature

Introduction: Thrombotic thrombocytopenic purpura (TTP) is a syndrome that consists of the pentad of thrombocytopenia, microangiopathic hemolytic anemia, neurologic abnormalities, fever and renal disease. Moskowitz was the first who described this syndrome in 1925, finding hyaline thrombi in many organs. The microthrombi cause tissue ischemia, platelet consumption, and microangiopathic hemolytic anemia. Brain involvement is common and leads to stroke, seizure, confusion, and headache. Renal injury occurs in a minority of patients and it is usually modest. Case report: We present a 57-year old male who came to our hospital because of weakness, prostration and darkening of his urine, occurring several days before admission. On physical examination we found icteric coloring of his skin and conjunctiva, big hematoma on his right lower leg and he had neurological abnormalities presented as mild headache, disorientation and aphasia. Laboratory tests revealed anemia and thrombocytopenia and the examination of peripheral blood smear showed presence of schistocytes. Direct and indirect antiglobulin test (Coombs) was negative. Emergency treatment was started with plasmapheresis on daily basis, immunosuppressive treatment with high-dose methylprednisolone and transfusions of red blood cells. The laboratory results and the clinical condition improved within two weeks. Conclusion: TTP is a medical condition that can be fatal if emergency treatment with plasmapheresis is not initiated presently after suspected diagnosis.

An Immunocompetent Case of Capnocytophaga canimorsus Infection Complicated by Secondary Thrombotic Microangiopathy and Disseminated Intravascular Coagulation

A 62-year-old woman with no previous history developed a Capnocytophaga canimorsus infection followed by thrombotic microangiopathy (TMA) and disseminated intravascular coagulation (DIC). She was treated with antibiotics and plasma exchange (PE) and recovered. C. canimorsus sepsis sometimes causes not only DIC but also TMA. The mortality of TMA is extremely high, so we should not hesitate to perform PE when a patient shows TMA symptoms.

Expert statement on the ICU management of patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is fatal in 90% of patients if left untreated and must be diagnosed early to optimize patient outcomes. However, the very low incidence of TTP is an obstacle to the development of evidence-based clinical practice recommendations, and the very wide variability in survival rates across centers may be partly ascribable to differences in management strategies due to insufficient guidance. We therefore developed an expert statement to provide trustworthy guidance about the management of critically ill patients with TTP. As strong evidence was difficult to find in the literature, consensus building among experts could not be reported for most of the items. This expert statement is timely given the recent advances in the treatment of TTP, such as the use of rituximab and of the recently licensed drug caplacizumab, whose benefits will be maximized if the other components of the management strategy follow a standardized pattern. Finally, unanswered questions are identified as topics of future research on TTP.

Vitamin B12 deficiency presenting as pseudo-thrombotic microangiopathy: a case report and literature review

Pseudo-thrombotic microangiopathy (pseudo-TMA) is a recognized, yet uncommon, clinical presentation of vitamin B12 deficiency. Patients with pseudo-TMA present with microangiopathic hemolytic anemia (MAHA), thrombocytopenia and schistocytes. They are often misdiagnosed as thrombotic thrombocytopenia purpura (TTP) and receive unnecessary therapy. Here, we report a case of a 60-year-old male who presented with thrombocytopenia and normocytic normochromic anemia. Anemia work-up was remarkable for severe B12 deficiency (<60 pg/mL) and a positive non-immune hemolysis panel. Peripheral smear was reviewed and showed anisocytes, poikilocytes, schistocytes and hypersegmented neutrophils. Vitamin B12 replacement (1000 mcg IM daily) was started, ADAMTS13 activity was sent and daily plasmapheresis was initiated. Over the next 3 days, the patient’s hemoglobin and platelets were stable and the hemolysis panel showed gradual improvement. On day 4, ADAMTS13 activity results came back normal at 61%. Accordingly, plasmapheresis was discontinued, parenteral B12 replacement was continued and that resulted in gradual improvement and eventually cessation of hemolysis and normalization of hemoglobin and platelets. In this patient, parietal cell autoantibodies were positive and so the diagnosis of pernicious anemia was made. Patients with severe vitamin B12 deficiency may present with features mimicking TTP such as MAHA, thrombocytopenia and schistocytosis. An early and accurate diagnosis of pseudo-TMA has a critical clinical impact with respect to administering the correct treatment with vitamin B12 replacement and avoiding, or shortening the duration of, unnecessary therapy with plasmapheresis.

Diagnostic Testing for Differential Diagnosis in Thrombotic Microangiopathies

Thrombotic microangiopathies (TMAs) are multiple disease entities with different etiopathogeneses, characterized by thrombocytopenia, microangiopathic hemolytic anemia (MAHA) with schistocytosis, variable symptoms including fever, and multi-organ failure such as mild renal impairment and neurological deficits. The two paradigms of TMAs are represented on one hand by acquired thrombotic thrombocytopenic purpura (TTP) and on the other by hemolytic uremic syndrome (HUS). The differential diagnosis between these two paradigmatic forms of TMA is based on the presence of either frank renal failure in HUS or a severe deficiency (<10%) of the zinc-protease ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) in TTP. ADAMTS13 is an enzyme involved in the proteolytic processing of von Willebrand factor (vWF), and its deficiency results in formation of high-molecular-weight vWF-rich microthrombi in the environment of the microvasculature. The presence of these ultra-large vWF multimers in the microcirculation can recruit platelets, promoting multi-organ ischemic lesions. The presence of ADAMTS13 activity at >10% could rule out the presence of a TTP form. However, it is often difficult to differentiate either a TTP or HUS clinical scenario presenting with typical symptoms of TMA. There are in fact several additional diagnoses that should be considered in patients with ADAMTS13 activity of >10%. Widespread inflammation with endothelial damage and adverse reactions to drugs play a central role in the pathogenesis of several forms of TMA, and in these cases, the differential diagnosis should be directed at the underlying disease. Hence, a correct etiologic diagnosis of TMA should involve a critical illness, cancer-associated TMA, drug-induced TMA, and hematopoietic transplant-associated TMA. A complete assessment of all the possible etiologies for TMA symptoms, including acquired or congenital TTP, will allow for a more accurate diagnosis and application of a more appropriate treatment.

Active Hepatitis C Leading to Refractory Thrombotic Thrombocytopenic Purpura - A Dubious Association and The Challenges Faced in Management

Acquired thrombotic thrombocytopenic purpura is a combination of thrombocytopenia with microangiopathic hemolytic anemia. A 62-year-old female was transferred from an outside hospital for rapidly worsening mental status and severe thrombocytopenia. Laboratory studies were significant for reduced hemoglobin and platelet count along with raised blood urea nitrogen, creatinine, and serum lactate dehydrogenase levels. Peripheral smear showed numerous schistocytes and further testing showed low ADAMTS13 activity, high ADAMTS13 inhibitor, and positive hepatitis C virus antibody with a high hepatitis C virus ribonucleic acid (RNA) load. The patient was diagnosed with acquired thrombotic thrombocytopenic purpura and started on plasma exchange and steroids. Since no response was achieved until day four of treatment, weekly rituximab was initiated. After the initial two doses of rituximab, she showed significant improvement clinically. ADAMTS13 levels returned back to normal. Cyclosporine was added, following which platelet counts were normalized. Cyclosporine was discontinued, plasma exchange and steroids were slowly tapered off. Follow-up visits showed that the patient is off treatment and continues to be in remission and on regular treatment for hepatitis C. Acquired thrombotic thrombocytopenic purpura is a hematological emergency. Our patient remained refractory to standard therapies and required rituximab and immunosuppressive agents like cyclosporine. We describe the association of active hepatitis C with acquired thrombotic thrombocytopenic purpura that was refractory to plasma exchange, high dose steroids and rituximab. As per our knowledge, this is the first case in the literature to describe a possible association between active hepatitis C and acquired thrombotic thrombocytopenic purpura.

Sepsis and septic shock: endothelial molecular pathogenesis associated with vascular microthrombotic disease

In addition to protective “immune response”, sepsis is characterized by destructive “endothelial response” of the host, leading to endotheliopathy and its molecular dysfunction. Complement activation generates membrane attack complex (MAC). MAC causes channel formation to the cell membrane of pathogen, leading to death of microorganisms. In the host, MAC also may induce channel formation to innocent bystander endothelial cells (ECs) and ECs cannot be protected. This provokes endotheliopathy, which activates two independent molecular pathways: inflammatory and microthrombotic. Activated inflammatory pathway promotes the release of inflammatory cytokines and triggers inflammation. Activated microthrombotic pathway mediates platelet activation and exocytosis of unusually large von Willebrand factor multimers (ULVWF) from ECs and initiates microthrombogenesis. Excessively released ULVWF become anchored to ECs as long elongated strings and recruit activated platelets to assemble platelet-ULVWF complexes and form “microthrombi”. These microthrombi strings trigger disseminated intravascular microthrombosis (DIT), which is the underlying pathology of endotheliopathy-associated vascular microthrombotic disease (EA-VMTD). Sepsis-induced endotheliopathy promotes inflammation and DIT. Inflammation produces inflammatory response and DIT orchestrates consumptive thrombocytopenia, microangiopathic hemolytic anemia, and multiorgan dysfunction syndrome (MODS). Systemic inflammatory response syndrome (SIRS) is a combined phenotype of inflammation and endotheliopathy-associated (EA)-VMTD. Successful therapeutic design for sepsis can be achieved by counteracting the pathologic microthrombogenesis.

Etiology and Outcomes of Thrombotic Microangiopathies

BACKGROUND AND OBJECTIVES

Thrombotic microangiopathies constitute a diagnostic and therapeutic challenge. Secondary thrombotic microangiopathies are less characterized than primary thrombotic microangiopathies (thrombotic thrombocytopenic purpura and atypical hemolytic and uremic syndrome). The relative frequencies and outcomes of secondary and primary thrombotic microangiopathies are unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a retrospective study in a four-hospital institution in 564 consecutive patients with adjudicated thrombotic microangiopathies during the 2009-2016 period. We estimated the incidence of primary and secondary thrombotic microangiopathies, thrombotic microangiopathy causes, and major outcomes during hospitalization (death, dialysis, major cardiovascular events [acute coronary syndrome and/or acute heart failure], and neurologic complications [stroke, cognitive impairment, or epilepsy]).

RESULTS

We identified primary thrombotic microangiopathies in 33 of 564 patients (6%; thrombotic thrombocytopenic purpura: 18 of 564 [3%]; atypical hemolytic and uremic syndrome: 18 of 564 [3%]). Secondary thrombotic microangiopathies were found in 531 of 564 patients (94%). A cause was identified in 500 of 564 (94%): pregnancy (35%; 11 of 1000 pregnancies), malignancies (19%), infections (33%), drugs (26%), transplantations (17%), autoimmune diseases (9%), shiga toxin due to Escherichia coli (6%), and malignant hypertension (4%). In the 31 of 531 patients (6%) with other secondary thrombotic microangiopathies, 23% of patients had sickle cell disease, 10% had glucose-6-phosphate dehydrogenase deficiency, and 44% had folate deficiency. Multiple causes of thrombotic microangiopathies were more frequent in secondary than primary thrombotic microangiopathies (57% versus 19%; P<0.001), and they were mostly infections, drugs, transplantation, and malignancies. Significant differences in clinical and biologic differences were observed among thrombotic microangiopathy causes. During the hospitalization, 84 of 564 patients (15%) were treated with dialysis, 64 of 564 patients (11%) experienced major cardiovascular events, and 25 of 564 patients (4%) had neurologic complications; 58 of 564 patients (10%) died, but the rates of complications and death varied widely by the cause of thrombotic microangiopathies.

CONCLUSIONS

Secondary thrombotic microangiopathies represent the majority of thrombotic microangiopathies. Multiple thrombotic microangiopathies causes are present in one half of secondary thrombotic microangiopathies. The risks of dialysis, neurologic and cardiac complications, and death vary by the cause of thrombotic microangiopathies.

A case report of a child with sepsis induced multiorgan failure and massive complement consumption treated with a short course of Eculizumab: A case of crosstalk between coagulation and complement?

RATIONALE

This article describes a child with a life-threatening multiorgan failure with disseminated intravascular coagulation (DIC) and massive complement consumption. To our knowledge this therapeutic approach was for the first time effectively applied in a pediatric patient.

PATIENT CONCERNS

A 14-month-old boy was presented with a severe, rapidly progressing, life-threatening disease because of sudden onset of fever, hemathemesis, hematuria, and bloody diarrhoea alongside fast spreading hematomas and general corporeal edema.

DIAGNOSIS

The most plausible diagnosis in our patient is Clostridium difficile sepsis-induced thrombotic microangiopathy alongside with DIC and consumption coagulopathy. The diagnosis was confirmed by positive C difficile bacteria strain in coproculture, clinical, and laboratory tests affirming DIC and global complement activation and consumption.

INTERVENTIONS

The patient was treated with antibiotics (Metronidazole, Vancomycin), plasmapheresis, dialysis, methylprednisolone, mycophenolate mofetil, and Eculizumab.

OUTCOMES

The child is in fair overall condition in a 2 year follow-up with no complications save chronic renal failure.

LESSONS

In rare cases of sepsis with massive complement consumption, a case-sensitive Eculizumab therapy may be at least considered after the resolution of life-threatening multiorgan failure. The application of this drug can be performed only after sepsis induced disease is put under control. A fast withdrawal of Eculizumab after control of massive complement consumption is recommended to prevent triggering of second sepsis reactivation.

Acute Hepatitis Caused by Genotype 4 HCV Presenting with Microangiopathic Hemolytic Anemia

Many cases have been reported about the role of chronic hepatitis C and interferon therapy in the development and recurrence of thrombotic thrombocytopenic purpura (TTP), but to our knowledge there is no previous report about the association between acute hepatitis C and any microangiopathic hemolytic anemia (MAHA) including TTP. We report a case of acute hepatitis C that presented with MAHA resembling TTP, which resolved with spontaneous clearance of viral infection.

Disseminated intravascular coagulation: is it fact or fancy?

: 'Disseminated intravascular coagulation (DIC)' occurs commonly in critical illnesses such as sepsis, trauma, cancer, and complications of surgery and pregnancy. Mortality is very high. The pathogenesis has been ascribed to tissue factor-initiated coagulation disorder, resulting in disseminated microblood clots that are made of platelets, plasma factors, fibrins, and blood cells. True DIC depletes coagulation factors and consumes platelets, and activates fibrinolysis. 'DIC' is assumed to orchestrate thrombocytopenia, microangiopathic hemolytic anemia and hypoxic multiorgan dysfunction syndrome, and causes hemorrhagic disorder due to depleted coagulation factors. In contrast, disseminated intravascular microthrombosis (DIT) occurs in thrombotic thrombocytopenic purpura (TTP) and TTP-like syndrome due to ADAMTS13 deficiency or insufficiency. The pathogenesis is due to formation of intravascular 'microthrombi' composed of complexes of platelets and unusually large von Willebrand factor multimers. Interestingly, DIT also occurs in the same critically ill patients as 'DIC' does. Following activation of complement system, the terminal complex C5b-9 causes endotheliopathy via channel formation to the endothelial cell membrane. Endotheliopathy activates microthrombotic pathway and initiates microthrombogenesis, leading to endotheliopathy-associated DIT. DIT results in TTP-like syndrome with hematologic phenotype of consumptive thrombocytopenia, microangiopathic hemolytic anemia, and multiorgan dysfunction syndrome. In reinterpretation of 'DIC', the true lesion is 'microthrombi' but not microblood clots. Thus, 'DIC' is endotheliopathy-associated DIT. This concept reconciles all the clinical features of 'DIC', and dramatically changes our understanding of pathophysiological mechanism in hemostasis and thrombosis. This new paradigm should assist the physician with correct diagnostic evaluation and treatment intervention.

Thrombotic thrombocytopenic purpura associated with dengue and chikungunya virus coinfection: case report during an epidemic period

The present report shows the occurrence of thrombotic thrombocytopenic purpura (TTP) associated with acute dengue and chikungunya virus coinfection, manifesting as a severe disease with high mortality potential. The patient was a 28 year-old man with clinical and epidemiological diagnosis of arboviruses infections who developed thrombocytopenia and anemia, after which oral corticosteroid therapy was started. On the third day of hospitalization, he showed neurological alterations that simulated a cerebral vascular accident, but the imaging examination did not identify ischemic or hemorrhagic alterations. At that moment, the TTP hypothesis was raised so that plasmapheresis and corticosteroid pulse therapy were started, have been essential for the favorable evolution of the case.

ADAMTS13: origins, applications, and prospects

ADAMTS13 is an enzyme that acts by cleaving prothrombotic von Willebrand factor (VWF) multimers from the vasculature in a highly regulated manner. In pathologic states such as thrombotic thrombocytopenic purpura (TTP) and other thrombotic microangiopathies (TMAs), VWF can bind to the endothelium and form large multimers. As the anchored VWF chains grow, they provide a greater surface area to bind circulating platelets (PLTs), generating unique thrombi that characterize TTP. This results in microvasculature thrombosis, obstruction of blood flow, and ultimately end-organ damage. Initial presentations of TTP usually occur in an acute manner, typically developing due to an autoimmune response toward, or less commonly a congenital deficiency of, ADAMTS13. Triggers for TMAs that can be associated with ADAMTS13 deficiency, including TTP, have been linked to events that place a burden on hemostatic regulation, such as major trauma and pregnancy. The treatment plan for cases of suspected TTP consists of emergent therapeutic plasma exchange that is continued on a daily basis until normalization of PLT counts. However, a subset of these patients does not respond favorably to standard therapies. These patients necessitate a better understanding of their diseases for the advancement of future therapeutic options. Given ADAMTS13's key role in the cleavage of VWF and the prevention of PLT-rich thrombi within the microvasculature, future treatments may include anti-VWF therapeutics, recombinant ADAMTS13 infusions, and ADAMTS13 expression via gene therapy.

TTP-like syndrome: novel concept and molecular pathogenesis of endotheliopathy-associated vascular microthrombotic disease

TTP is characterized by microangiopathic hemolytic anemia and thrombocytopenia associated with brain and kidney dysfunction. It occurs due to ADAMTS13 deficiency. TTP-like syndrome occurs in critically ill patients with the similar hematologic changes and additional organ dysfunction syndromes. Vascular microthrombotic disease (VMTD) includes both TTP and TTP-like syndrome because their underlying pathology is the same disseminated intravascular microthrombosis (DIT). Microthrombi are composed of platelet-unusually large von Willebrand factor multimers (ULVWF) complexes. TTP occurs as a result of accumulation of circulating ULVWF secondary to ADAMTS13 deficiency. This protease deficiency triggers microthrombogenesis, leading to "microthrombi" formation in microcirculation. Unlike TTP, TTP-like syndrome occurs in critical illnesses due to complement activation. Terminal C5b-9 complex causes channel formation to endothelial membrane, leading to endotheliopathy, which activates two different molecular pathways (i.e., inflammatory and microthrombotic). Activation of inflammatory pathway triggers inflammation. Activation of microthrombotic pathway promotes platelet activation and excessive endothelial exocytosis of ULVWF from endothelial cells (ECs). Overexpressed and uncleaved ULVWF become anchored to ECs as long elongated strings to recruit activated platelets, and assemble "microthrombi". In TTP, circulating microthrombi typically be lodged in microvasculature of the brain and kidney, but in TTP-like syndrome, microthrombi anchored to ECs of organs such as the lungs and liver as well as the brain and kidneys, leading to multiorgan dysfunction syndrome. TTP occurs as hereditary or autoimmune disease and is the phenotype of ADAMTS13 deficiency-associated VMTD. But TTP-like syndrome is hemostatic disorder occurring in critical illnesses and is the phenotype of endotheliopathy-associated VMTD. Thus, this author's contention is TTP and TTP-like syndrome are two distinctly different disorders with dissimilar underlying pathology and pathogenesis.

Heparin-induced thrombocytopenia associated with thrombotic microangiopathy

Some cases of thrombotic microangiopathy (TMA) are refractory to plasma exchange therapy (PE) with persistence or recurrence of thrombocytopenia. We report two patients suffering from TMA of different aetiologies (associated with disseminated malignancy, typical haemolytic uraemic syndrome) with recurrent or persistent thrombocytopenia despite adequate therapy including PE. Since both patients were exposed to unfractionated heparin, heparin-induced thrombocytopenia (HIT) was suspected as a cause. Pretest probabilities for HIT were intermediate. ELISA for PF4/heparin antibodies was strongly positive in both cases, and HIT was confirmed by heparin-induced platelet activation assay. Anticoagulation with lepirudin was initiated, with subsequent rapid increase of the platelet count.

TMA might represent a predisposition for HIT. This could be due to TMA-related platelet activation with increased PF4 release. In TMA patients exposed to heparin and with refractory or rapidly recurrent thrombocytopenia HIT should always be considered as a possible cause.

Leptospirosis presenting as haemolytic uraemic syndrome: a case report

Background

Leptospirosis is a rare infectious disease especially in Western Countries. Renal involvement is a recognised complication of leptospirosis but leptospirosis-associated haemolytic uraemic syndrome is extremely rare and to our knowledge has only been reported once, in 1985.

Case presentation

A 29-year-old male was transferred to our Renal Unit with fevers, myalgia and diarrhoeal illness. Laboratory investigations revealed an acute kidney injury, acute liver injury, significantly raised lactate dehydrogenase with marked anaemia, thrombocytopenia and schistocytes on a blood film. A diagnosis of haemolytic uraemic syndrome was made. Surprisingly, the stool culture was negative which led to a suspicion of leptospirosis as one of the differential diagnoses. This was subsequently confirmed by enzyme-linked immunosorbent assay and microscopic agglutination test. He received plasma exchange and antibiotics and made a complete recovery on discharge.

Conclusion

Leptospirosis presenting as haemolytic uraemic syndrome is rare but should be considered in the differential diagnosis especially in the presence of significant liver injury, as current evidence suggests that the disease is re-emerging.

A STARD-compliant prediction model for diagnosing thrombotic microangiopathies

Aim of the study was the definition of a predictive model for the initial diagnosis of thrombotic microangiopathies (TMA). We retrospectively collected data on all adult patients admitted to the Gemelli Hospital from 2010 to 2014. ICD-9 codes from primary diagnoses were used for TMA diagnosis. Demographic and laboratory characteristics on admission of patients with TMA were then compared with a random sample of 500 patients with other diagnoses. The prediction model was externally validated in a cohort from another hospital. Overall, 23 of 187,183 patients admitted during the study period received a primary diagnosis of TMA. LDH (OR 1.26, 95% CI 1.05, 1.63) and platelets (OR 0.96, 95% CI 0.94, 0.98) were the only independent predictors of TMA. The AUROC of the final model including only LDH and platelets was 0.96 (95% CI 0.91, 1.00). The Hosmer-Lemeshow (HL) test (p = 0.54) suggested good calibration. Our model also confirmed good discriminatory power (AUROC 0.72 95% CI 0.60, 0.84) and calibration (HL test p = 0.52) in the validation sample. We present a simple prediction model for use in diagnosing TMA in hospitalized patients. The model performs well and can help clinicians to identify patients at high risk of TMA.

Platelet dysfunction contributes to bleeding complications in patients with probable leptospirosis

BACKGROUND

Severe leptospirosis is frequently complicated by a hemorrhagic diathesis, of which the pathogenesis is still largely unknown. Thrombocytopenia is common, but often not to the degree that spontaneous bleeding is expected. We hypothesized that the hemorrhagic complications are not only related to thrombocytopenia, but also to platelet dysfunction, and that increased binding of von Willebrand factor (VWF) to platelets is involved in both platelet dysfunction and increased platelet clearance.

METHODOLOGY/PRINCIPAL FINDINGS

A prospective study was carried out in Semarang, Indonesia, enrolling 33 hospitalized patients with probable leptospirosis, of whom 15 developed clinical bleeding, and 25 healthy controls. Platelet activation and reactivity were determined using flow cytometry by measuring the expression of P-selectin and activation of the αIIbβ3 integrin by the binding of fibrinogen in unstimulated samples and after ex vivo stimulation by the platelet agonists adenosine-diphosphate (ADP) and thrombin-receptor activating peptide (TRAP). Platelet-VWF binding, before and after VWF stimulation by ristocetin, as well as plasma levels of VWF, active VWF, the VWF-inactivating enzyme ADAMTS13, thrombin-antithrombin complexes (TAT) and P-selectin were also measured. Bleeding complications were graded using the WHO bleeding scale. Our study revealed that platelet activation, with a secondary platelet dysfunction, is a feature of patients with probable leptospirosis, especially in those with bleeding manifestations. There was a significant inverse correlation of bleeding score with TRAP-stimulated P-selectin and platelet-fibrinogen binding (R = -0.72, P = 0.003 and R = -0.66, P = 0.01, respectively) but not with platelet count. Patients with bleeding also had a significantly higher platelet-VWF binding. Platelet counts were inversely correlated with platelet-VWF binding (R = -0.74; P = 0.0009. There were no correlations between platelet-VWF binding and the degree of platelet dysfunction, suggesting that increased platelet-VWF binding does not directly interfere with the platelet αIIbβ3 signaling pathway in patients with probable leptospirosis.

CONCLUSION/SIGNIFICANCE

Platelet dysfunction is common in probable leptospirosis patients with manifest bleeding. Increased VWF-platelet binding may contribute to the activation and clearance of platelets.

Relapse of congenital thrombotic thrombocytopenic purpura, after spontaneous remission, in a second-trimester primigravida: case report and review of the literature

CONTEXT

Thrombotic microangiopathy syndrome or thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) describes distinct diseases sharing common pathological features: microangiopathic hemolytic anemia and thrombocytopenia, without any other apparent cause.

CASE REPORT

An 18-year-old second-trimester primigravida presented with a history of fifteen days of intense weakness, followed by diarrhea over the past six days. She reported having had low platelets since childhood, but said that she had never had bleeding or menstrual abnormalities. Laboratory investigation showed anemia with schistocytes, thrombocytopenia and hypohaptoglobulinemia. Red blood cell concentrate and platelet transfusions were performed. The hypothesis of TTP or HUS was put forward and ADAMTS13 enzyme activity was investigated. The patient evolved with increasing platelet counts, even without specific treatment, and she was discharged. One month afterwards, she returned presenting weakness and swollen face and legs, which had developed one day earlier. The ADAMTS13 activity was less than 5%, without presence of autoantibodies. Regarding the two previous admissions (at 9 and 16 years of age), with similar clinical features, there was spontaneous remission on the first occasion and, on the second, the diagnosis of TTP was suspected and plasmapheresis was performed, but ADAMTS13 activity was not investigated.

CONCLUSION

To date, this is the only report of congenital TTP with two spontaneous remissions in the literature This report reveals the importance of suspicion of this condition in the presence of microangiopathic hemolytic anemia and thrombocytopenia without any other apparent cause.

Development and validation of a multivariable prediction rule for detecting a severe acquired ADAMTS13 activity deficiency in patients with thrombotic microangiopathies

Background:

Thrombotic microangiopathies (TMAs) are a group of diseases that have different aetiologies and treatments, but a clinical differential diagnosis remains difficult. Among TMAs, thrombotic thrombocytopenic purpura (TTP) is characterised by a severe ADAMTS13 functional deficiency. However, assays exploring ADAMTS13 activity are limited to some specialised laboratories. Our objective was to develop and validate a diagnostic method for TTP in adult patients with TMA.

Methods:

We generated a multivariable model (four predictors) on a cohort of 174 TMA patients in order to predict an ADAMTS13 activity deficiency (AUC of 0.927). The multivariable model was simplified into a binary rule to facilitate the interpretation of the predictions. There were two scenarios for a patient: (1) Predicted ADAMTS13 deficiency; if the patient met four conditions simultaneously (platelets ≤44×109/L, creatinine ≤2 mg/dL (≤176.84 µmol/L) for males or ≤1.9 mg/dL (≤168 µmol/L) for females, age ≤68 years and no history of haematopoietic stem cell transplant [HSCT]); or (2) Predicted “normal” activity; if any of the above conditions are not met. This rule was validated on a second cohort of 86 patients and performed with sensitivity of 87.7% and specificity of 92.7%.

Results and conclusions:

This could lead to the earlier confirmation or rapid exclusion of TTP when ADAMTS13 testing is not avalilable, facilitating a more suitable therapy based on the aetiology of the TMA.

Complement-mediated thrombotic microangiopathy secondary to sepsis-induced disseminated intravascular coagulation successfully treated with eculizumab: A case report

Secondary thrombotic microangiopathies (TMAs) are induced by several underlying conditions; most are resolved by treating background disease. Eculizumab is a human monoclonal antibody that blocks the final stage of the complement system and effectively treats atypical hemolytic uremic syndrome (aHUS). In this report, we present a patient with TMA secondary to sepsis- induced coagulopathy, who was successfully treated with eculizumab.A 44-year-old woman, who had no special medical history or familial history of TMAs, was admitted on suspicion of septic shock. Physical examination revealed gangrene on her soles. Blood tests revealed a decreased platelet count, disseminated intravascular coagulation (DIC), renal dysfunction, hemolysis, and infection. Although the coagulation disorder improved with intensive care, the low platelet count, elevated lactate dehydrogenase levels, and renal dysfunction persisted. Our investigations subsequently excluded thrombotic thrombocytopenic purpura and Shiga toxin-producing Escherichia coli-induced HUS. Plasma exchange only improved lactate dehydrogenase levels. We clinically diagnosed this case as atypical HUS and started eculizumab treatment. The patient's platelet count increased, her renal dysfunction improved, and the gangrene on her feet was ameliorated. The patient was discharged without maintenance dialysis therapy after approximately 3 months. Subsequent tests revealed elevated serum levels of soluble C5b-9, and genetic testing revealed compound heterozygous c.184G > A (Val62Ile) and c.1204T > C (Tyr402His) single-nucleotide polymorphisms in complement factor H.We encountered a case of complement-mediated TMA accompanied by DIC, which was successfully treated with eculizumab. Further studies are necessary to support the optimal use of eculizumab for TMA with background diseases.

Severe Staphylococcus aureus Endocarditis Presenting as Peripartum Thrombotic Thrombocytopenic Purpura

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening illness that occurs in both pregnant and non-pregnant women. Several other conditions can mimic the disease, which makes the diagnosis challenging.

CASE

We describe a case of severe Staphylococcus aureus endocarditis that initially presented as peripartum TTP in a 39-year-old woman at 29+6 weeks' gestation. We give an overview of the diagnostic considerations and management of thrombocytopenia in pregnancy and review the literature related to TTP and peripartum infective endocarditis.

CONCLUSION

Given the significant differences in definitive therapies for the spectrum of thrombocytopenic conditions that occur in pregnancy, timely and accurate diagnosis of TTP is critical for optimal management.

Thrombotic Microangiopathy Care Pathway: A Consensus Statement for the Mayo Clinic Complement Alternative Pathway-Thrombotic Microangiopathy (CAP-TMA) Disease-Oriented Group

Thrombotic microangiopathies (TMAs) comprise a heterogeneous set of conditions linked by a common histopathologic finding of endothelial damage resulting in microvascular thromboses and potentially serious complications. The typical clinical presentation is microangiopathic hemolytic anemia accompanied by thrombocytopenia with varying degrees of organ ischemia. The differential diagnoses are generally broad, while the workup is frequently complex and can be confusing. This statement represents the joint recommendations from a multidisciplinary team of Mayo Clinic physicians specializing in the management of TMA. It comprises a series of evidence- and consensus-based clinical pathways developed to allow a uniform approach to the spectrum of care including when to suspect TMA, what differential diagnoses to consider, which diagnostic tests to order, and how to provide initial empiric therapy, as well as some guidance on subsequent management.