1
Année 2017/2018 N°
Thèse
Pour le
DOCTORAT EN MEDECINE
Diplôme d’État par
Guillaume BAYER
Né le 30 janvier 1986, à Creil (60)
Etiologies et présentation initiale des micro-angiopathies thrombotiques prises en charge au Centre Hospitalier
Universitaire de Tours entre 2009 et 2016
Présentée et soutenue publiquement le 14 février 2018, devant un jury composé de :
Président du Jury :
Professeur François MAILLOT, Médecine Interne, Faculté de Médecine – Tours Membres du Jury :
Professeur Jean-Michel HALIMI, Néphrologie-Immunologie clinique, Faculté de Médecine – Tours Professeur Emmanuel GYAN, Hématologie et thérapie cellulaire, Faculté de Médecine – Tours
Docteur Elisabeth DIOT, Médecine Interne, PH, CHU – Tours
Docteur Christelle BARBET, Néphrologie-Immunologie clinique, PH, CHU – Tours
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SERMENT D’HIPPOCRATE
E
n présence des Maîtres de cette Faculté, de mes chers condiscipleset selon la tradition d’Hippocrate,
je promets et je jure d’être fidèle aux lois de l’honneur et de la probité dans l’exercice de la Médecine.
Je donnerai mes soins gratuits à l’indigent,
et n’exigerai jamais un salaire au-dessus de mon travail.
Admis dans l’intérieur des maisons, mes yeux ne verront pas ce qui s’y passe, ma langue taira les secrets qui me seront confiés et mon état ne servira pas
à corrompre les mœurs ni à favoriser le crime.
Respectueux et reconnaissant envers mes Maîtres, je rendrai à leurs enfants
l’instruction que j’ai reçue de leurs pères.
Que les hommes m’accordent leur estime si je suis fidèle à mes promesses.
Que je sois couvert d’opprobre et méprisé de mes confrères
si j’y manque.
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Initial presentation and management of thrombotic micro- angiopathy in a university hospital: 564 case series
Keywords: Secondary thrombotic micro-angiopathy, hemolytic uremic syndrome, thrombotic thrombocytopenic purpura
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Abstract
Introduction: Thrombotic microangiopathies (TMA) are potentially serious diseases characterized by hemolytic
anemia with schizocytosis, thrombocytopenia and organ injury. Several causes are well individualized:
ADAMTS13-related thrombotic thrombocytopenic purpura (TTP), Shiga-toxin related-hemolytic uremic syndrome (HUS), and Complement-related atypical hemolytic uremic syndrome (aHUS). Many other causes have been described but they are generally considered as a cause of TMA in only a minority of patients.
However, very few reports have been published on the issue. The objective of the present study was to assess the proportion of different causes of TMA in a university hospital, and to analyze their initial presentation, management and outcome. Patients and Methods: Two modes of detection were used: either the presence of a schistocytosis ≥ 0.5 % on a blood smear and/or the presence of specific keywords in hospitalization discharge summaries of all patients hospitalized at Tours university hospital (France), between 2009 and 2016 included.
Patients were included in case of microangiopathic hemolytic anemia associated with thrombocytopenia.
Results: TMA occurred in 564 patients hospitalized in 19 different medical and surgical departments. TMA was
associated with different conditions, mainly pregnancy (35 %), infection without Shiga-toxin (33 %), medication (26 %), and cancer (18 %). TPP, HUS and aHUS represented together less than 13 % of cases. All TMA included, half of patients had multiple causes, especially in transplant-associated TMA. Some characteristics were significantly different according to the etiology, including the presence of cardiac involvement (more common in infection without Shiga-toxin or malignant hypertension), the need for dialysis (more frequent in HUS, aHUS and malignant HTA), and mortality (more common in PTT and cancer). Complement abnormalities were found in many other etiologies than aHUS. Discussion: This work showed that secondary TMA are more frequent than it is usually suggested. Conditions of TMA are often associated, especially infections without Shiga-toxin, malignancies and drugs. Additional causes of TMA are also found in TTP and aHUS. The fact that TMA can occur in distinct situations leads to variable management and could explain that delayed diagnosis is frequent and etiological workup generally poor, which can increase complications.Conclusion: Pathophysiology of TMA involves multiple mechanisms which can be unspecific and frequently associated in various degrees, leading to different clinical patterns. It highlights the need for interdisciplinary approaches and for education of a wide range of front-line clinicians to increase awareness of TMA.
Keywords: Secondary thrombotic micro-angiopathy, hemolytic uremic syndrome, thrombotic thrombocytopenic purpura
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Résumé
Introduction: Les micro-angiopathies thrombotiques (MAT) regroupent diverses pathologies relativement rares
mais potentiellement graves. Certaines étiologies sont maintenant bien définies: le purpura thrombotique thrombocytopénique (PTT), le syndrome hémolytique et urémique (SHU) et le syndrome hémolytique et urémique atypique (SHUa). Les nombreuses autres causes de MAT sont généralement considérées comme minoritaires mais les données sont rares et parcellaires. L’objectif de ce travail était d’évaluer la proportion des différentes étiologies de MAT, leurs caractéristiques et leurs prises en charge au sein d’un centre hospitalier universitaire (CHU). Patients et Méthode: La sélection des patients a été réalisée en utilisant 2 modes d’identification: la présence d’une schizocytose ≥ 0.5 % et/ou la présence de mot-clé(s) spécifiques dans un compte-rendu d’hospitalisation, au CHU de Tours (France) entre 2009 et 2016 inclus. Ont été retenus comme MAT, après validation par un comité d’adjudication, les cas d’anémie hémolytique mécanique avec thrombopénie périphérique. Résultats: Le diagnostic de MAT a été retenu pour 564 patients, hospitalisés dans 19 services différents. La MAT était associée à diverses situations, principalement la grossesse (35 %), les infections sans Shiga-toxine (33 %), les médicaments (26 %) et les cancers (18 %). Le PTT, le SHU et le SHUa représentait à eux trois moins de 13% des cas. Toutes MAT incluses, la moitié des patients avaient plusieurs étiologies, en particulier en cas de greffe. Certaines caractéristiques cliniques et biologiques étaient significativement différentes en fonction de l’étiologie, notamment la présence d’une atteinte cardiaque (plus fréquente en cas d’infection ou d’HTA maligne), la nécessité de recourir à la dialyse (plus fréquent en cas de SHU, de SHUa ou d’HTA maligne) ou encore la mortalité (plus fréquente en cas de PTT ou de cancer).
Discussion: Ce travail montre que les MAT secondaires sont plus fréquentes que ce qui est habituellement
suggéré. Les causes sont souvent associées, en particulier les infections sans Shiga-toxine, les cancers et les médicaments. Des causes multiples peuvent également être retrouvées au cours des PTT et SHUa. Le fait que les MAT puissent se produire dans des situations cliniques très différentes rend leur prise en charge variable d’un service hospitalier à l’autre et pourrait expliquer que le diagnostic soit parfois retardé et le bilan étiologique souvent incomplet. Conclusion : La physiopathologie des MAT implique différents mécanismes qui peuvent être aspécifiques et fréquemment associés à divers degrés, conduisant à différents tableaux cliniques. Cela souligne l’intérêt d'une approche multidisciplinaire et de la sensibilisation d'un large éventail de cliniciens de spécialités différentes, afin d’améliorer la prise en charge des MAT.
Mots clés: micro-angiopathies thrombotiques secondaires, purpura thrombotique thrombocytopénique, syndrome hémolytique et urémique
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Table des matières:
Introduction page 11
Patients and Methods page 12
Figure 1 page 14
Results page 15
Table 1 page 16
Figure 2 page 17
Table 2 page 18
Table 3 page 19
Table 4 page 20
Table 5 page 21
Table 6 page 23
Figure 3 page 24
Table 7 page 24
Discussion page 25
Conclusion page 31
References page 32
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Introduction
Thrombotic microangiopathies (TMA) represent a final common pathway of rare but potentially serious diseases. They are characterized by hemolytic anemia with schizocytosis, thrombocytopenia and organ injury (predominantly the kidney and the brain), caused by arteriolar and capillary thrombosis with characteristic endothelial abnormalities. [1]
Several causes of TMA are well individualized: thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), and atypical hemolytic uremic syndrome (aHUS). TTP is defined by a severe decrease of ADAMTS13 activity. A marked decreased of ADAMTS13, which cleaves the coagulation protein von Willebrand factor, leads to platelet aggregation. [2]
Hereditary TTP (5 to 10 % of cases) is caused by homozygous or compound heterozygous ADAMTS13 mutations. [3] Most causes of acquired TTP (90 to 95 % of cases) are caused by inhibition of ADAMTS13 activity by auto-antibodies. [4] HUS usually occurs in children, after gastrointestinal infection with Shiga-toxin producing Escherichia coli (STEC). Shiga- toxin (Stx) binds to the glycolipid Gb3, triggers activation of endothelial cells, platelets and coagulation cascade, and leads to thrombus formationwith accompanying renal impairment.
[5,6] Atypical HUS is caused by uncontrolled activation of the complement alternative pathway due to mutations or auto-antibodies. [7-10]
Many other causes of TMA have been described (such as drugs, malignant hypertension, infections without Stx, malignancies, autoimmune diseases, transplant, pregnancy, genetic cobalamin C deficiency, or sickle cell disease) [11-13] but they are generally considered as a cause of TMA in only a minority of patients. [14] However, very few reports have been published on the issue and whether secondary TMA represent a sizable part of all TMA is unclear. [15,16] In addition, secondary TMA represent a diagnostic and therapeutic challenge as it may affect patients of all ages, with various comorbid conditions. Unsurprisingly, it was shown that patients with TTP are not always identified [17]. This may due to the fact that the
12 highly variable presentation (age, comorbid conditions, severity of TMA) of patients who are admitted to many medical departments. It is presently unknown how patients with TMA from other causes are identified and managed. The objective of the present study was to assess the proportion of different causes of TMA in a university hospital, and to analyze their initial presentation, management and outcome.
Patients and methods
Selection of patients
Patients hospitalized at Tours university hospital (France), between January 1st, 2009 and December 31th, 2016 who had a suspicion of TMA were included in the present study. Two modes of detection were used (Fig.1): (1) either the presence of a schistocytosis ≥ 0.5 % on a blood smear (using DxLab software version 4.23.18) and/or (2) the presence of specific keywords in all hospitalization discharge summaries (HDS) (using Castor software version 3.0). Keywords were: "thrombotic microangiopathy", "thrombotic micro-angiopathy",
"thrombotic micro angiopathy", "TMA", "thrombotic thrombocytopenic purpura", "TTP",
"hemolytic uremic syndrome", "HUS", "schistocytes", "schistocytosis", "ADAMTS13",
"decreased haptoglobin", "malignant hypertension", and "HELLP". All HDS with at least one of these keywords and/or related to a patient with schistocytosis ≥ 0.5 % was analyzed by physicians (AB, BT, FVT, GB). All patients’ files were analyzed individually (manually) using all available data, including HDS and computerized database. When a patient was admitted to several units, HDS of each unit and relevant biochemical and clinical data were analyzed but the patient was recorded once.
13 Of note, Tours hospital is the unique university hospital in the Centre area of France (population estimate: 2,100,000 persons) and during the 2009-2016 period, 510,627 patients were admitted to this hospital.
Definition and causes of TMA
Patients were included in case of microangiopathic hemolytic anemia (hemoglobin < 12 g/dL, with increased LDH, decreased haptoglobin, and schizocytosis ≥ 0.5 %) associated with thrombocytopenia (platelets count < 150 G/L). Some cases were considered as TMA despite the absence of one of these criteria when other data clearly suggested the existence of TMA.
Diagnostic of TTP, HUS and aHUS was respectively retained when ADAMTS13 activity was severely decreased (usually < 5 %, with or without anti-ADAMTS13 antibodies), Stx or Stx- producing bacteria was documented, or abnormality of the alternative pathway of complement was detected (with or without identified genetic mutation).
Adjudication committee
All cases of TMA were adjudicated by a committee (CV, FF, J-MH). When data were insufficient to conclude, additional information was sought. When discordance appeared, a consensus among members was obtained.
Flow chart
Finally, 564 patients were analyzed, as shown in the flow chart (Figure 1). Schistocytosis permitted to include 278 patients, and keywords in HDS 398 patients (112 patients were detected by both methods).
Statistical analysis
Quantitative data are presented as mean and standard deviation (SD) for normally distributed variables and median, first and third quartiles for variables with skewed distributions.
Qualitative data are described with percentages. Comparisons were made using the Chi square
14 test for qualitative data and Wilcoxon test for quantitative data. SAS software version 9.3 was used. A p value < 0.05 was considered as significant.
Ethics
Approval of the Ethics Committee of our institution was obtained (research project n° 2017 003).
* Keywords in hospitalization discharge summaries (HDS): "thrombotic microangiopathy", "thrombotic micro-angiopathy",
"thrombotic micro angiopathy", "TMA", "thrombotic thrombocytopenic purpura", "TTP", "hemolytic uremic syndrome",
"HUS", "schistocytes", "schistocytosis", "ADAMTS13", "decreased haptoglobin", "malignant hypertension", and "HELLP".
Figure 1. Flow chart Schistocytosis ≥ 0.5 %
n = 364 patients
Keywords found in HDS*
n = 1289 patients
Missing data n = 2 patients
Already detected (presence of schistocytosis) n = 124 patients
Suspicion of TMA : adjudication n = 740 patients
Before 2009 / another hospital n = 126 patients
Other diagnosis n = 44 patients
Keyword not related to patient n = 12 patients
Missing data n = 9 patients
Other diagnosis n = 596 patients
TMA n = 564 patients TMA excluded
n = 176 patients
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Results
Baseline characteristics
Baseline characteristics of these 564 patients are presented in Table 1. Mean age of patients was 37 [27-57] years (including 3.4 % <18), and the female to male sex ratio was 62.6 %.
Neurologic symptoms were observed in 43.8 % of patients. Diarrhea was present in 16.4 % of patients and de novo hypertension in 49.7 % (Table 1).
Patients had typical biological presentation of TMA including anemia, thrombocytopenia and low haptoglobin, elevated lactate dehydrogenase (LDH) in virtually all patients, and schistocytosis in most patients (hemoglobin: 83 [68-102] g/L, platelet count: 63 [31-105] G/L, low haptoglobin: 90.4 %, (LDH): 3 [2-5] fold upper limit of normal (ULN); schistocytosis:
79.3 %) (Table 1). Acute kidney injury was present in 57.7 % of patients, and hepatic cytolysis in 66 % of patients (Table 1).
These patients were hospitalized in 19 different medical and surgical departments (Fig. 2), mainly obstetrics and gynecology (33.5 %), nephrology (21.3 %), pediatrics (9.6 %), internal medicine (7.8 %), and hematology and oncology (6.9 %). Overall, 352 patients (62.4 %) were admitted to intensive care unit (ICU) during their hospitalization.
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Clinical characteristics
Age (years) 37 (27-57)
- Age < 18 years (%) 3.4
- Age > 65 years (%) 20.7
Sex (% females) 62.6
Neurologic symptoms (%) 43.8
- Consciousness disturbance (%) 18.2
- Headache (%) 17.7
- Visual disturbances (%) 9.5
- Focal deficit (%) 6.1
- Epileptique seizure (%) 5.5
Hypertension (%) 49.7
Diarrhea (%) 16.4
Purpura (%) 6.4
Biological characteristics
Anemia (%) 96.5
- Hemoglobin levels (g/dL) 83 (68-102) - Mean globular volume (fL) 91 (87-103)
Presence of schistocytes (%) 79.3
- Schistocytes levels (‰) 6 (2-19)
Thrombocytopenia (%) 92.2
- Platelet count (G/L) 63 (31-105)
Neutropenia (%) 8.5
- PMN levels (G/L) 7.8 (3,9-11.9)
Lactate deshydrogenase (x ULN) 3 (2-5)
Low haptoglobin levels (%) 90.4
Undetectable haptoglobin levels (%) 74.6
Elevated bilirubin levels (%) 49.1
Hepatic cytolysis (%) 66.0
Serum albumin (g/L) 29 (25-33)
Prothrombin time (%) 77 (58-96)
Fibrinogen (g/L) 3.90 (2.60-5.00)
Disseminated intravascular coagulation (%) 9
CRP > 10 mg/L (%) 66.9
Acute kidney injury (%) 57.7
- Serum creatinine (µmol/L) 106 (70-257) - Blood urea nitrogen (mmol/L) 9.8 (5.3-22.0)
Proteinuria (%) 86.2
Table 1. Baseline characteristics
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*: Other medical departments: Infectious diseases (2 %), cardiology (1.4 %), pneumology (1.2 %), rheumatology (0.9 %), neurology (0.5 %), dermatology (0.5 %), and geriatrics (0.5 %).
Figure 2. Hospitalization services of patients with TMA
Causes of TMA
Identification of the causes of TMA
As shown in Table 2, TMA was associated or the result of with different medical conditions.
Pregnancy-related TMA represented the most frequent cause of TMA. Other frequent causes included infections without STEC, drugs and cancer.
Regarding TMA related to infections without STEC, bacteria, virus and parasites could be a cause of TMA. The cause of infection was identified in more than half of patients and severe sepsis was present in 43.5 % of cases.
Obstetrics 33%
Nephrology 21%
Pediatrics 10%
Internal medicine 8%
ICU only 7%
Hematology Oncology
7%
Hepatology 5%
Other*
7%
Surgery 2%
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Etiologies of TMA N (%)
TTP 18 (3.2 %)
HUS (STEC+) 33 (5.9 %)
aHUS 21 (3.7 %)
Infection (STEC-) 186 (33 %)
Severe sepsis 81 (43.5 %)
Documented infection 153 (82.3 %) - Documented bacteria 93 (60.8 %) - Documented virus 78 (51 %) - Documented parasite 18 (11.8 %) - Several infectious agents 41 (26.8 %)
Cancer 104 (18.4 %)
Solid tumor 57 (54.8 %)
- Adenocarcinoma 45 (78.9 %) Hematological malignancy 49 (47.1 %) - Acute leukemia 19 (38.8 %)
- Lymphoma 15 (30.6 %)
Medication 144 (25.5 %)
Anticalcineurin 98 (68.1 %)
Gemcitabine 11 (7.6 %)
Transplant 96 (17 %)
Solid transplant 67 (69.8 %)
HSC transplant 29 (30.2 %)
Pregnancy 197 (34.9 %)
HELLP 167 (84.8 %)
Autoimmune disease 48 (8.5 %)
Lupus 14 (29.2 %)
Antiphospholipid syndrome 10 (20.8 %)
Scleroderma 8 (16.7 %)
Malignant hypertension 21 (3.7 %)
Sickle cell disease 16 (2.8 %)
Acute pancreatitis 3 (0.5 %)
Of note, some patients had more than one cause of TMA
Table 2. Etiologies of TMA
19 HUS (STEC), aHUS and PTT according to age
Overall, STEC, aHUS and TTP occurred in 5.9 %, 3.7 % and 3.2% of patients with TMA, aHUS and TTP together contributing to less than 12.8 % of patients with TMA (Table 2).
Almost 90 % of patients with TMA did not have TTP, aHUS or STEC in adult patients. TTP and aHUS occurred in 3 quarters of cases in patients in the 18-60 age group (Table 3). As shown in Table 3, STEC mainly occurred in patients <18 (97 %); however, STEC represented only 53.3 % of patients <18 with TMA (Table 3).
Table 3. Contribution of STEC, aHUS and TTP among causes of TMA according to age
Evidence for multiple risk factors or causes within the same patients with TMA
All TMA included, only 50.5 % of patients had a single cause of TMA (Table 4). However, some causes of TMA were unfrequently associated with additional risk factor such as infection without STEC, cancer, drug or transplantation (STEC, pregnancy) (Table 4). In contrast, drug and transplant-related TMA were almost always associated with other causes (Table 4). It was quite difficult to ascertain the primary cause of TMA when 3 or 4 risk factors were present.
Multiple causes were also frequent in malignant hypertension and immune disease (Table 4).
Table Y: Contribution of STEC, aHUS and TTP among causes of TMA according to age
<18 18-60 >60 all
STEC 97.0 0 3.0 100
aHUS 9.5 76.2 14.3 100
TTP 5.6 77.8 16.7 100
<18 18-60 >60 all
STEC 53.3 0 0.9 5.9
aHUS 3.3 4.1 2.6 3.7
TTP 1.7 3.6 2.6 3.2
all 3 58.3 7.8 6.0 12.8
p value: <0.0001 for both analyses
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All TTP
HUS
(STEC+) aHUS Pregnancy Infection (STEC-) Drugs Cancer Transplant
Auto-immune disease
Malignant hypertension
n=562** n=18 n=31** n=21 n=197 n=186 n=144 n=104 n=96 n=48 n=21
Only cause (%) 50.5 61.1 100 66.7 90.4 50.0 6.3 17.3 0 43.8 57.1
Number of additional causes* (%)
1 21.4 27.8 0 0 8.6 15.6 40.3 41.4 33.3 33.3 14.3
2 14.4 5.6 0 19.1 1.0 25.3 41.7 25.0 49.0 12.5 9.5
3 10.7 5.6 0 9.5 0 9.1 11.8 16.4 17.7 10.4 9.5
4 3.0 0 0 4.8 0 - - - - 0 9.5
*: among infection without Shiga-toxin (STEC-), drugs, cancer, and transplant
**: 2/564 patients with HUS had missing data
Table 4. Number of additional causes of TMA
Presentation of TMA in relation to the cause of TMA
Although all patients had classical features of TMA (anemia, thrombopenia, low haptoglobin, elevated LDH, schistocytes), significant clinical and biological differences were observed among TMA causes (Table 5).
Diarrhea was observed in all patients regardless of the cause except in those with pregnancy, even in the absence of STEC (Table 5).
The lowest hemoglobin levels were found in patients with TTP or STEC (Table 5). Platelet count was lower in TTP than in most other causes (Table 5). PT was lower in patients with cancer whereas fibrinogen was lower in patients with cancer or TTP as compared to other causes of TMA (Table 5). All causes of TMA were associated with acute kidney injury (AKI) but AKI was observed in more than 75% of patients with malignant hypertension, auto- immune disease, drug, TTP, and STEC (Table 5). Expectedly, the combination of serum creatinine < 200 µmol/L and platelet count < 30 G/L was more frequent in case of TTP (77.8
%, p <0.0001) than in other causes of TMA (Table 5).
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Diagnosis workup in patients with TMA
As shown in Table 6, etiological diagnosis workup was generally limited. ADAMTS13 and Complement assays were ordered in, respectively, 22.2 % and 51.4 % of patients. In accord of the consensual definition of these etiologies, decreased ADAMTS13 activity was observed in most TTP (94.4 %), and abnormalities in alternative complement pathway were detected in 79
% of aHUS (Table 6).
However, decreased ADAMTS13 activity was also observed in other etiologies than TTP (infection without STEC: 16.7 %, cancer: 9.1 %, auto-immune disease: 5.6 %, drugs: 4.4 %), and Complement abnormalities were found in all other causes of TMA, including 12.5 % of TTP (transplant: 26.8 %, auto-immune disease: 25.7 %, infection without STEC: 21.1 %, malignant hypertension: 20 %, drugs: 19.7 %, cancer: 18.8 %, pregnancy: 5.6 %). In patients with aHUS, ADAMTS13 activity was never <10 % but assay was performed in only 57.2 % of cases (Table 6).
Although diarrhea was frequent, Shiga-toxin was researched in a minority of patients (16.4 %) but its presence was highly specific to HUS (100 %; other etiologies: 0 %) (Table 6).
Although hemolysis was observed in most patients, Coombs test was ordered in a minority of patients (10.8 %). It was positive in 16.4 % of cases (especially in auto-immune disease: 35.7
%, infection without STEC: 33.3 %, and transplant: 33.3 %) (Table 6), which could delay the diagnosis of TMA by referring to another cause of hemolysis.
Antinuclear antibodies was researched in 49.5 % of cases, mostly in TTP (88.9 %) and auto- immune disease (87.5 %) (Table 6). It was positive for 14.2 % of patients, including 76.2 % of auto-immune disease and 62.5 % of TTP, and, more surprisingly, 75 % of aHUS, 64.7 % of malignant hypertension, 48.8 % of infection without STEC, and 47 % of pregnancy (Table 6).
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All patients TTP
HUS
(STEC+) aHUS Pregnancy
Infection
(STEC-) Drugs Cancer Transplant
Auto-immune disease
Malignant hypertension
Ordered lab tests n=564 n=18 n=33 n=21 n=197 n=186 n=144 n=104 n=96 n=48 n=21
Alternative Complement pathway % 51.4 100 66.7 90.5 49.2 43.0 44.4 38.5 42.7 77.1 95.2
abnormalities % 15.1 12.5 4.8 79.0 5.6 21.1 19.7 18.8 26.8 25.7 20.0
ADAMTS13 activity % 22.2 100 0 57.1 15.2 22.6 15.9 21.2 10.4 37.5 0
value<10%* % 13.6 94.4 - 0 0 16.7 4.4 9.1 0 5.6 -
Coombs test % 10.8 22.2 0 28.6 1.5 14.5 13.4 16.3 6.3 13.5 28.6
positive % 16.4 0 - 0 0 33.3 14.3 11.8 33.3 35.7 16.7
Antinuclear antibodies % 49.5 88.9 12.1 57.1 61.4 43.0 32.6 38.5 27.1 87.5 81.0
positive % 14.2 62.5 25.0 75.0 47.1 48.8 42.6 37.5 34.6 76.2 64.7
Shiga-toxin % 30.3 22.2 84.8 23.8 39.1 18.3 16.7 0 9.4 10.6 28.6
positive % 16.4 0 100 0 0 0 0 - 0 0 0
*: all but one patients with low ADAMTS13 value were adjudicated as TTP
Table 6. Diagnosis workup in patients with TMA
Complications during hospitalization and patient outcome
Cardiac and renal complications were frequent. Patients developed major cardiovascular event (MACE, i.e. acute coronary syndrome and/or acute heart failure) (11.4%), needed dialysis (19.7%), and 10.3 % of patients died, respectively, during hospitalization (Figure 3).
MACE was more frequent in patients with infection without STEC, TTP, and malignant hypertension, whereas dialysis was more frequent in patients with STEC, aHUS, and malignant hypertension (Table 7). Patients with TTP and cancer were those with the highest mortality rate. The death rate was very high in patients with TTP (6/18); however, it is important to note that 2/6 who died were not admitted to ICU during hospitalization. No death occurred during HUS and pregnancy.
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*: MACE: major cardiovascular events (heart failure or acute coronary syndrome)
Figure 3. Complications according to the etiology of TMA
Stepwise multivariate analysis*
OR 95%CI p value
MACE**
TTP 2.16 0.70-1.81 0.1787
Pregnancy 0.31 0.13-0.74 0.0083
Infection (STEC-) 3.30 1.83-5.95 <0.0001
Transplantation 0.52 0.24-1.09 0.0838
Dialysis
Cancer 0.45 0.23-0.87 0.0179
aHUS 4.34 1.66-11.4 0.0028
Infection (STEC-) 1.85 1.15-2.96 0.0112
Death
TTP 6.03 1.98-18.4 0.0016
Cancer 3.63 1.91-6.90 <0.0001
infection (STEC-) 2.99 1.64-5.46 0.0004
Transplant 0.40 0.16-0.96 0.0395
*: all models included age and sex; all causes of TMA were included in the models, except STEC and pregnancyfor the risk of death, and STEC for the risk of MACE
**: MACE: major cardiovascular events (heart failure or acute coronary syndrome)
Table 7. Outcome of patients according to the cause of TMA
0 10 20 30 40 50 60 70 80
MACE*, dialysis and death in patients with TMA
MACE Dialysis Death
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Discussion
In this large cohort, our aim was to estimate a least-biased incidence of secondary TMA in a university hospital, to assess their current management and outcome. Our main findings are that 1) aHUS and TTP represent less than 7 % of all causes of TMA whereas non-Stx related infections, drugs, cancer, and pregnancy-related represent more than two thirds of TMA; 2) over 46 % of patients, especially those with secondary TMA, have more than one cause of TMA, so that it is difficult to assess with certainty the primary cause of TMA; 3) specific lab tests (alternative complement pathway, ADAMTS13, Coombs, Shiga-toxin) are ordered in a minority of patients; and 4) that the outcome of TMA remains poor with a high risk of dialysis, MACE and death.
Incidence and causes
This work showed that secondary TMA are more frequent than it is usually suggested. In our university hospital (all units included), TMA occured in more than 0.1 % of patients, but TPP, HUS and aHUS represented together less than 13 % of cases. The causes of secondary TMA were very diverse but 4 clinical situations were more often observed: infections (STEC excluded), cancer, medication, and pregnancy.
Infection-associated TMA (STEC-)
More than 30 different bacteria have been associated with TMA in the literature, but virus can also be involved (mostly HIV and CMV). TMA have also been reported during parasitosis, such as aspergillosis, cryptosporidiosis and malaria. [18-23] In our series, almost a third of all TMA was associated with an infectious condition (excepted HUS). We found more than 20 different infectious agents (mainly Gram negative bacilli) but virus (such as HIV, CMV, EBV, influenza A, and parvovirus B19) were also frequently found. Malaria was the most
26 frequent parasitosis and concerned 6 % of infection-associated TMA. Multiple infections and severe sepsis were relatively frequent.
Pathophysiology of infection-associated TMA could involve non-specific systemic inflammation (including cytokines and neutrophil extracellular traps release, complement activation and hemostasis alteration) [13,24] or microbial toxins (other than Shiga-toxin).
Indeed, data showed that Pneumococcus can release an enzyme that leads to hemolysis, thrombocytopenia, and microthrombi. [19] Moreover, the fact that TMA sometimes occured epidemically in children with Plasmodium vivax infection has suggested another specific toxin-induced effect. However, the pathogenesis of microvascular thrombi in malaria mainly involves parasitized erythrocytes aggregation, platelets and endothelial cells activation, and impairment of vasomotor responses. [23,25,26]
Cancer-associated TMA
In our study, 18 % of TMA were associated with cancer. According to the literature, almost 6
% of patients with metastatic cancer could have TMA, mainly in case of mucin-producing adenocarcinoma, but also in lymphoma and other malignancies. [27-29] In our series, more than 30 different malignancies were found, with a majority of adenocarcinoma (77 % of solid tumors).
Cytokines such as tumor necrosis factor (TNF) may participate to endothelial activation.
Coagulation disorders may also be involved and DIC is not rare. It has been speculated that mucin may exert a direct deleterious effect on the injured endothelium, affecting its production and release of von Willebrand factor. [24,27-29] Moreover, metastatic micro- emboli could induce the occlusion of microvessels and local increase of vascular endothelial growth factor (VEGF): in pulmonary tumor thrombotic microangiopathy syndrome, tumor cell embolization to the pulmonary vasculature leads to severe pulmonary hypertension and
27 right heart failure, with a poor prognosis. [30]. It could explain that respiratory impairment is more frequent in paraneoplastic TMA than in other etiologies such as TTP. [24,27,29]
Drug-induced TMA
TMA due to antineoclastic drugs are usually related to the cumulative dose and may only manifest several months after the end of treatment, even when cancer is in remission. The incidence could reach 28 % with mitomycin C and 4 % with gemcitabine. [13,29] The main other chemotherapeutic agents involved are 5-fluorouracil, bleomycin, vincristine, and platinum salts. Anti-VEGF therapies represent another kind of antineoplastic agent that can induce TMA. [29, 31-34] Non antineoplastic drugs can also trigger TMA, mainly calcineurin inhibitors (cyclosporine, tacrolimus, everolimus), for which the toxicity is dose-dependant (the signs of TMA typically resolve after discontinuing or decreasing the dose). [34,35] Many other drugs have been associated with TMA but the causal association is clearly demonstrated mainly for interferon, penicillin, quinine, and clopidogrel (all found in our series). [34,36,37]
Drug-induced TMA are mainly due to direct endothelial-cell injury (especially with chemotherapic agents and antiangiogenic therapies), but immunological disorders could also be involved, such as cytokines release, endothelial deposition of immune complexes, and production of platelets autoantibodies (especially during quinine, gemcitabine or oxaliplatin- induced TMA). [29,34,32,36,38]
Pregnancy-associated TMA
In the literature, pregnancy-associated TMA account for 8 to 18 % of all TMA. [39] In our series, it represented more than one third. The hemolysis-elevated liver enzymes-and-low platelets (HELLP) syndrome is the most common etiology (78 % in our series), with an incidence that could reach 0.9 % of all pregnancies. HELLP syndrome is often associated
28 with preeclampsia (97 % in our series) and occur mainly in the third trimester and early post- partum. [39-41]
In HELLP syndrome, abnormal placentation and maternal immunological maladaptation are the most important triggers of TMA, inducing excessive inflammatory response, antiangiogenic factors production and coagulation disorders (such as alteration of plasminogen activation and increased level of von Willebrand factor multimers). The hepatocyte necrosis is due to specific toxicity of placenta-derived factors (inducing local increase of TNF) combinated to the thrombotic obstruction of the sinusoids. Recently, implication of insufficient mitochondrial oxidation of fatty acids has also been suggested.
[11,39-41]
Other secondary TMA
The main other conditions of TMA found in our series were transplant (17 %), dysimmune disease (9 %), malignant hypertension (4 %), and sickle cell disease (SCD) (3 %).
Multiple causes
Associated secondary TMA
This study showed that conditions of TMA are often associated (half of the cases). Infection without STEC, cancer and medication were the most frequent additional causes.
Multiple causes were especially found in transplant-associated TMA, which represented 39 % of TMA in neoplastic context. According to the literature, TMA could occur after more than one third of allogeneic HSC transplantation. Opportunistic infections and calcineurin inhibitors (used to prevent graft rejection) are the most common associated factors.
[21,22,29,42] Noticeably, in our series, CMV replication was found in 19 % of transplanted patients. Recent data suggests that graft-versus-host disease (GVHD) could be an independant risk factor (present in 16 % of our transplanted patients). [43] Additionally, surgery and
29 ischemia-reperfusion injury could promote early TMA after solid organ transplantation [44], and total body irradiation may increase the risk of later TMA after allogeneic HSC transplantation. [42,43]
In our series, malignant hypertension was associated with another potential condition of TMA in 43 % of cases. Otherwise, severe hypertension is frequently observed in other etiologies of TMA such as preeclampsia or scleroderma renal crisis, and the distinction can be sometimes difficult, probably because it exists overlapping forms. Indeed, in systemic scleroderma- associated TMA, histologic renal lesions are similar to those observed in idiopathic malignant hypertension, and in both cases, thrombocytopenia usually returns to within the normal range once blood pressure is controlled. [45] Pathogenesis involves vasoconstriction and endothelial injury, and may be shear stress dependant, possibly due to activation of von Willebrand factor, decreased bioavailability of nitric oxide (NO) and activation of the renin-angiotensin system. As in other TMA conditions, ADAMTS13 activity can be decreased and complement dysregulation can be observed (genetic impairement of complement regulation could even exceed two third of patients). [46,47]
Hemolysis could be another inductive factor. Indeed, authors showed that in SCD and malaria, free plasma hemoglobin and other microparticules due to erythrocyte fragmentation can promote vasoconstriction, endothelial impairement and thrombosis, by decreasing NO bioavailability and by activating platelets, complement and coagulation cascade. More globally, as hypertension, this hemolysis-mediated pathophysiological mechanism could be an autoamplification signal in all TMA etiologies. [48]
Additional causes of TMA in TTP and aHUS
The estimation of TTP relapse during pregnancy varies from 23 to 66 % in the literature, and it could concern 0.001 to 0.05 % of all pregnancies. Most of the cases occurre during the second and third trimesters, probably because the progressive physiological decrease of
30 ADAMTS13 potentiates the inhibitory effect of anti-ADAMTS13 autoantibodies. Regarding aHUS, relapse rate during pregnancy could be around 20 %. [11,39-41,49]. In our series, 10
% of patients with aHUS were pregnant.
Infection also frequently triggers acute episode of congenital TTP or aHUS (about 70 % of patients with aHUS in the literature). Additionaly, as other autoimmune diseases, acquired TTP can be induced by bacterial or viral infection. [4,13,18,24,50] HIV-associated TMA with anti-ADAMTS13 autoantibodies occurs mainly in patients with a low immune deficiency but various disturbances in CD4+ T cells functions. [11,13,20,24] In our series, 37 % of TTP and 14 % of aHUS were associated with an infectious condition.
Furthermore, our study confirme the fact that Complement abnormalities can be found in other etiologies than aHUS, including TTP and HUS (STEC+).
Difficult diagnosis and poor prognosis
In our series, as it is usually observed, TMA was not always identified by physicians, and complications (such as MACE, AKI requiring dialysis and death) were frequent. The fact that TMA can occur in distinct situations involves that patients can be hospitalized in many different medical and surgical departments, leading to variable management of the TMA. It could explain that etiological workup is generally poor. Moreover, discrepant results may confuse the picture. Because delay in the diagnosis and treatment may result in irreversible end-organ damage and higher mortality, authors have recently suggested the need for interdisciplinary approaches and for education of a wide range of front-line clinicians to increase awareness of TMA. [11,12, 51]
31
Conclusion
Pathophysiology of TMA involves multiple mechanisms leading to endothelial injury and platelet aggregation. They can be highly specific to an etiology (Shiga-toxin in HUS, collapsed ADAMTS13 in TTP, hepatotoxicity of placenta-derived factors in HELLP) but in most cases they are unspecific and associated in various degrees, leading to different clinical patterns (Complement dysregulation, inflammation, hemostasis perturbation, severe hypertension). Some of these conditions are constitutional (aHUS, TTP, SCD), placing patients at enhanced risk for further development of TMA. Even within HUS, clinical phenotype depends on the type and number of genetic mutations in Complement genes. [10- 12] For all these reasons, TMA classification is complex, and nosology should change in the future. Furthermore, a multidisciplinary approach seems necessary to improve management of patients and knowledge in pathogenesis.
32
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Vu, le Directeur de Thèse
Vu, le Doyen De la Faculté de Médecine de Tours
Tours, le
