Abstracts
BACKGROUND:
It has been demonstrated that neutrophils, eosinophils and monocytes, under appropriated stimulus, may express tissue factor and therefore, activate the extrinsic pathway of coagulation. We performed a transversal and case-control study of patients with chronic urticaria and patients with psoriasis, in our outpatient clinic to evaluate the production of D-dimer.
OBJECTIVE:
To evaluate D-dimer serum levels in patients with chronic urticaria and its possible correlation with disease activity.
PATIENTS AND METHODS:
The study was conducted from October 2010 until March 2011. We selected 37 consecutive patients from our Allergy Unit and Psoriasis Unit, and divided them into three groups for statistical analysis: (i) 12 patients with active chronic urticaria (CU); (ii) 10 patients with chronic urticaria under remission and (iii) 15 patients with psoriasis (a disease with skin inflammatory infiltrate constituted by neutrophils, lymphocytes and monocytes). Another five patients with urticarial vasculitis were allocated in our study, but not included in statistical analysis. The serum levels of D-dimer were measured by Enzyme Linked Fluorescent Assay (ELFA), and the result units were given in ng/ml FEU.
RESULTS:
Patients with active chronic urticaria had the highest serum levels of D-dimer (p<0.01), when compared to patients with CU under remission and the control group (patients with psoriasis).
CONCLUSIONS:
Patients with active chronic urticaria have higher serum levels of D-dimer, when compared to patients with chronic urticaria under remission and patients with psoriasis. We found elevated serum levels of D-dimer among patients with urticarial vasculitis.
Angioedema; Psoriasis; Urticaria; Vasculitis; Vasculitis, leukocytoclastic, cutaneous
FUNDAMENTOS:
Tem sido demonstrado que os neutrófilos, eosinófilos e monócitos, sob estímulo apropriado, podem expressar fator tecidual e, portanto, ativar a via extrínseca da coagulação. Realizamos um estudo transversal e caso-controle de pacientes com urticária crônica e pacientes com psoríase em nosso ambulatório para avaliar a produção de dímero-D.
OBJETIVO:
Avaliar níveis de dímero-D em pacientes com urticária crônica e sua possível correlação com a atividade da doença.
PACIENTES E MÉTODOS:
O estudo foi conduzido de outubro de 2010 até março de 2011. Nós selecionamos 37 pacientes consecutivos da Unidade de Alergia e Unidade de Psoríase, divididos em três grupos para análise estatística: (i) 12 pacientes com urticária crônica ativa; (ii) 10 pacientes com urticária crônica em remissão e (iii) 15 pacientes com psoríase (uma doença com a pele infiltrado inflamatório constituído por neutrófilos, linfócitos e monócitos). Outros cinco pacientes com vasculite urticariforme foram alocados em nosso estudo, mas não incluídos na análise estatística. Os níveis séricos de D-dímero foram medidos por Enzyme Linked Fluorescent Assay (ELFA), e os resultados foram medidos em ng / ml FEU.
RESULTADOS:
Os pacientes com urticária crônica ativa tinham níveis séricos mais altos de dímero-D (p <0,01), quando comparados aos pacientes com urticária crônica em remissão e ao grupo controle (pacientes com psoríase).
CONCLUSÕES:
Os pacientes com urticária crônica ativa têm níveis séricos mais elevados de dímero-D, quando comparados aos pacientes com urticária crônica em remissão e aos pacientes com psoríase. Encontramos níveis elevados de dímero-D entre os pacientes com vasculite urticariforme.
Angioedema; Psoríase; Urticária; Vasculite; Vasculite leucocitoclástica cutânea
INTRODUCTION
Chronic urticaria (CU) has a wide spectrum of clinical presentations and possible etiologies.11. Bindslev-Lensen C, Finzi A, Greaves M, Camarasa J, Ortonne JP, Schöpf E, et al. Chronic urticaria: diagnostic recommendations. J Eur Acad Dermatol. 2000; 14:175-80.
2. Nettis E, Pannofino, Uappile C, Ferrannini A, Tursi A. Clinical and aetiological aspects in urticaria and angio-oedema. Br J Dermatol. 2003;148:501-6.
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33. Wisnieski JJ. Urticarial vasculitis. Curr Opin Rheumatol. 2000;12:24-31. The pathogenesis of CU includes immunological and nonimmunological types and an idiopathic type. Moreover, it has been recently associated with the presence of histamine-releasing IgG autoantibodies, found in 50% of cases previously considered of unknown cause, which characterizes the autoimmune urticaria.44. Grattan C, Sabroe R, Greaves M. Chronic urticaria. J Am Acad Dermatol. 2002;46:645-57. Urticaria is caused by degranulation of cutaneous mast cells and/or basophils. Degranulation releases potent vasoactive mediators that induce vasodilatation and increased capillary permeability, resulting in erythema and wheal formation. Itching and pain are caused by sensory nerve stimulation. The main vasoactive mediator is histamine, but there are other inflammatory mediators such as arachidonic acid metabolites, leukotrienes (LTC4, D4 and E4), prostaglandin D2, serotonin, acetylcholine, platelet activating factor, heparin, codeine, anaphylatoxins C3, C5a, quinones and neurotransmitters released from cutaneous nerve endings.55. Hein R. Chronic urticaria: impact of allergic inflammation. Allergy. 2002;57:S19-24. Degranulation is related to immunological causes (IgE, immune complexes, complement dependent), non-immunological causes (pseudoallergic, infectious or due to direct action of agents released by mast cells) and idiopathic. One of the most important factors that induce degranulation of mast cells in chronic urticaria is the presence of histamine IgG releasing autoantibodies against α-subunit IgE high affinity receptor (FcεRIα) or against IgE, which has been demonstrated in 50% of patients with chronic idiopathic urticaria.66. Zuberbier T, Henz B, Fiebiger E, Stingl M. Anti-FceRI serum autoantibodies in different subtypes of urticaria. Allergy. 2000;55:951-4.
,
77. Sabroe RA, Fiebiger E, Francis DM, Maurer D, Seed PT, Grattan CE, et al. Classification of anti-FcepsilonRI and anti-IgE autoantibodies in chronic idiopathic urticaria and correlation with disease severity J Allergy Clin Immunol. 2002;110:492-9.
Recent reports revealed that patients with CU show signs of thrombin generation and activation of the tissue factor pathway of the coagulation cascade.88. Cugno M, Marzano AV, Asero R, Tedeschi A. Activation of blood coagulation in chronic urticaria: pathophysiological and clinical implications. Intern Emerg Med. 2010;5:97-101. D-dimer (DD) is a fibrin degradation product formed during the lysis of a thrombus. DD elevations are detected in plasma during the onset of thrombus formation and its elevation usually lasts about a week. For this reason, it is possible to find high levels of DD during increased fibrinolytic activity. It occurs in high concentrations in many clinical conditions, such as deep vein thrombosis and pulmonary embolism. It may be also be elevated in myocardial infarction, disseminated intravascular coagulation, pneumonia, heart failure, neoplasia, polytrauma or in patients undergoing surgery. Currently, elevated DD has also been associated with severity and activity of chronic urticaria.99. Ver Elst K, Jochmans K, De Pauw A, De Waele M. Plasma D-dimer concentrations in different clinical conditions. Acta Clin Belg. 2002;57:325-30. , 1010. Asero R, Tedeschi A, Cugno M. Heparin and tranexamic acid therapy may be effective treatment -resistant chronic urticarial with elevated D-dimer: a pilot sudy. Int Arch Allergy Inmunol. 2010;152:384-9. The normal serum level of DD is less than 500 micrograms/litre. The serum levels of D-dimer were measured by Enzyme Linked Fluorescent Assay (ELFA), and the result units were given in ng/mL FEU - fibrinogen equivalent unit. A positive value was over 200 ng/mL FEU, with a negative result when the final value was less than that.
There are few reports about the relationship between DD levels and chronic urticaria and its role in this disease, which led us to make this work.
PATIENTS AND METHODS
The study population comprised patients with chronic urticaria (more than 6 weeks of disease), attending our outpatient clinic (Allergy Unit) from October 2010 to March 2011. The inclusion criterion was the clinical and histopathologic diagnosis of chronic urticaria (CU) and exclusion criteria were the diagnosis of other diseases that could alter the coagulation cascade, or the use of anticoagulant therapy. The control population consisted of patients with psoriasis, from our outpatient clinic (Psoriasis Unit).
The design of this research was descriptive and transversal case-control. The first and second groups of patients with chronic urticaria that underwent ddimer levels measurements were classified as: active (symptomatic) CU (12 patients) and CU under remission (10 patients). Fifteen volunteers with psoriasis constituted the third group.
The active CU group was defined as patients showing the presence of active cutaneous lesions as urticarial plaques, using hydroxyzyne and loratadine. This group consisted of 12 patients, ten females and two males, with ages ranging from 24 to 69 years old, (mean age 37.5 years).
There were 10 patients in the CU group in remission (seven females and three males; aged between 28-49 years old, with mean age of 39.3 years). For remission criteria we established that the patients must have been without urticaria or angioedema lesions for a minimum period of 30 days and under treatment with antihistamines (hydroxyzine plus loratadine).
The control group was composed of 15 patients with psoriasis (seven females and eight males; range 28-53 years-old, mean age 42.4 years).
Five patients with chronic, active lesions resembling urticaria, with histopathologic findings that further revealed leukocytoclastic vasculitis, indicating the diagnosis of urticarial vasculitis, were also included as a separate group. We evaluated D-dimer serum levels in this group of patients. However we did not include these patients in the statistical analysis due to the small number of cases.
The serum levels of D-dimer were measured by Enzyme Linked Fluorescent Assay (ELFA), and the result was given in ng/mL FEU (fibrinogen equivalent unit).
Study design and Statistical analysis
This is a transversal case-control study. The potential differences in D-dimer levels between patients with active CU, compared with CU patients under remission and controls (patients with psoriasis) were calculated by application of Pearson's Chisquared test.
RESULTS
All demographic data and D-dimer levels of the patients allocated in the study are described in table 1.
Elevated serum levels of D-dimer were found in 12 out of 22 patients with chronic the active urticaria (54.5%). The average D-dimer level was 869 ng/mL FEU; with the normal level being less than 500 ng/mL FEU. The remaining 10 patients with chronic urticaria under remission (45.5%) presented normal levels of DD (average 339 ng/mL FEU). In the control group (patients with psoriasis), only one patient exceeded the normal levels of the D-dimer, the others had normal levels with an average of 337 ng/mL FEU (Table 2).
After applying the tests of mean differences between patients with chronic urticaria with activity and under remission, the difference between the two groups was significant (p<0.01). Also, we calculated the odds ratio (OR) and it revealed that patients with chronic urticaria have OR = 18.0, for elevated D-dimer levels, compared with patients with psoriasis (Graph 1).
In three patients with urticarial vasculitis the disease was idiopathic during the study. One patient (case 4) had antiphospholipid antibodies and ANA positive. The D-dimer levels were elevated in all 5 patients with urticarial vasculitis (Table 3).
Demographic data and frequency of elevated D-dimer levels among patients with urticarial vasculitis
DISCUSSION
Skin reactivity to the intradermal injection of autologous serum (autologous serum skin test - ASST) and/or plasma (autologous plasma skin test - APST) has been proposed to identify chronic urticaria (CU) patients with an autoimmune or auto reactive disease.1111. Asero R, Cugno M, Tedeschi A. Activation of blood coagulation in plasma from chronic urticaria patients with negative autologous plasma skin test. J Eur Acad Dermatol Venereol. 2011;25:201-5.
Immune-mediated inflammation and coagulation are strictly linked, and coagulation activation has been described in CU patients as shown by the elevations of plasma prothrombin fragment F1+2 and Ddimer.1111. Asero R, Cugno M, Tedeschi A. Activation of blood coagulation in plasma from chronic urticaria patients with negative autologous plasma skin test. J Eur Acad Dermatol Venereol. 2011;25:201-5.
In CU, several investigators have demonstrated that the activation of coagulation is due to the involvement of eosinophils and a tissue factor pathway, with generation of thrombin potentially contributing to an increased vascular permeability. CU patients often present elevation of coagulation and fibrinolysis markers, such as prothrombin fragment F1+2 and Ddimer, which correlate with the disease severity.1111. Asero R, Cugno M, Tedeschi A. Activation of blood coagulation in plasma from chronic urticaria patients with negative autologous plasma skin test. J Eur Acad Dermatol Venereol. 2011;25:201-5. Preliminary data indicate that anticoagulant treatment with heparin and warfarin may be effective in reducing the symptoms of CU. All these findings provide the rationale for proposing clinical trials on the use of anticoagulant drugs as adjuvant treatment in CU patients.88. Cugno M, Marzano AV, Asero R, Tedeschi A. Activation of blood coagulation in chronic urticaria: pathophysiological and clinical implications. Intern Emerg Med. 2010;5:97-101.
Asero et al. correlated the presence of intense activity of the coagulation cascade with exacerbations of lesions in patients with chronic urticaria.1111. Asero R, Cugno M, Tedeschi A. Activation of blood coagulation in plasma from chronic urticaria patients with negative autologous plasma skin test. J Eur Acad Dermatol Venereol. 2011;25:201-5. Recent reports revealed that patients with CU show signs of thrombin generation and activation of the tissue factor pathway of the coagulation cascade and autologous plasma skin tests score positive in as many as 95% of cases.1212. Asero R, Tedeschi A, Coppola R, Griffini S, Paparella P, Riboldi P, et al. Activation of the tissue factor pathway of blood coagulation in patients with chronic urticaria. J Allergy Clin Immunol. 2007;119:705-10. Moreover, CU patients showing positive response to ASST had plasma profile of the urokinase system-associated proteins, which was not markedly different as compared with CU patients with negative ASST as well as healthy subjects, suggesting that systemic fibrinolysis may not be involved in chronic urticaria.1313. Kasperska-Zajac A, Brzoza Z, Rogala B. Blood urokinase plasminogen activator system in chronic urticaria. Arch Dermatol Res. 2007;298:409-11.
In our study we also observed increased serum levels of D-dimer among patients with active CU and patients with urticarial vasculitis in all patients.
Mast cells, essential elements involved in the pathogenesis of CU, produce GM-CSF (granulocytemacrophage colony-stimulating factor) and PAF (platelet-activating factor).1414. Breitenstein A, Camici GG, Tanner FC. Tissue factor: beyond coagulation in the cardiovascular system. Clin Sci (Lond). 2010;118:159-72. These factors stimulate resting eosinophils, inducing translocation of encrypted Tissue Factor (TF) to cytoplasmatic membrane, which will activate blood coagulation system.1414. Breitenstein A, Camici GG, Tanner FC. Tissue factor: beyond coagulation in the cardiovascular system. Clin Sci (Lond). 2010;118:159-72.
In CU, some authors have demonstrated that generation of thrombin could potentially be contributing to an increased vascular permeability, because thrombin may activate PAR-1 on endothelial cells, amplifying the inflammatory response in urticaria88. Cugno M, Marzano AV, Asero R, Tedeschi A. Activation of blood coagulation in chronic urticaria: pathophysiological and clinical implications. Intern Emerg Med. 2010;5:97-101.. Mast cells express both PAR-1 and PAR-2. The thrombin generated may activate mast cells via PAR-1 and the complexes TF+FVIIa and FVa+FXa may activate these cells via PAR-2, amplifying the continuous activation of mast cells in CU.1515. Dugina TN, kiseleva EV, Chistov IV, Umarova BA, Strukova SM. Receptors of the PAR family as a link between blood coagulation and inflammation. Biochemistry (Moscow). 2002;67:65-74. (Figure 1).
Proposition of events involving the coagulation cascade in chronic urticaria: During activation of mast cells occurs the release of vasoactive amines (mainly histamine), eicosanoids, and cytokines. Histamine H1 receptors act on endothelial cells promoting vasodilatation and increasing capillary permeability. GM-CSF (Granulocyte/macrophage colony-stimulating factor) and PAF (platelet activating factor) are able to activate eosinophils in the dermis and promote the expression of tissue factor (TF) in their cytoplasm membrane. Activated eosinophils secrete major basic protein (MBP) that stimulates mast cells. Besides these events, TF generated by eosinophils may start the extrinsic pathway of coagulation forming the complex VIIa+TF, that together with complex Xa+Va, act in mast cells via protease activated receptor 2 (PAR2). Thrombin activates: (i) PAR 1 on endothelial cells leading to the secretion and expression of the mediators of inflammation and anticoagulants (ICAM-1, NO and others); (ii) PAR1 of mast cells inducing the secretion of pro-inflammatory (histamine, PAF, cytokines, and others) and anti-inflammatory (heparin, NO) mediators. The fibrin is then degraded by fibrinolytic system in fibrin degradation products (FDP), including d-dimer, which can be detected in peripheral blood. Abbreviations: PAR, protease activated receptor; ICAM, intercellular adhesion molecule; NO, nitric oxide
Our results are similar to those obtained by Asero et al, in that the use of D-dimer levels in the blood of patients with chronic urticaria could be a potential serum marker to withdraw antihistamine treatment, as there is a decrease in their values.1212. Asero R, Tedeschi A, Coppola R, Griffini S, Paparella P, Riboldi P, et al. Activation of the tissue factor pathway of blood coagulation in patients with chronic urticaria. J Allergy Clin Immunol. 2007;119:705-10. New prospective studies that include serum D-dimer level analysis in a larger number of patients with chronic urticaria, before and during treatment, are needed to accomplish this use.
To the best of our knowledge, the finding of elevated levels of d-dimer in the blood of patients with urticarial vasculitis has not been reported in the literature. Currently, it is known that tissue factor can be found encrypted (inactive) in the cytoplasm of various peripheral blood cell elements, such as monocytes, eosinophils, neutrophils and platelets.1616. Osterud B. Tissue factor expression in blood cells. Thromb Res. 2010;125:S31-4.
The exposure of subendothelial TF to blood after vessel injury is a critical step in hemostasis and in the pathogenesis of arterial and venous thrombotic disorders. Moreover, there is an additional role for overexpression of TF and subsequent generation of TF: FVIIa complex, FXa and thrombin have recently emerged as contributors in non-thrombotic manifestations such as inflammation, cancer growth and fibrosis.1717. Mitroulis I, Kambas K, Anyfanti P, Doumas M, Ritis K. The multivalent activity of the tissue factor-thrombin pathway in thrombotic and non-thrombotic disorders as a target for therapeutic intervention. Expert Opin Ther Targets. 2011;15:75-89.
Urticarial vasculitis usually presents with a considerable number of intact and degenerated neutrophils, resulting in "nuclear dust", which together with edema of the dermis and fibrinoid necrosis of small diameter blood vessels of the superficial dermis compose the typical histopathology pattern of this disease.1818. Criado PR, Criado RFJ, Maruta CW, Martins JEC, Rivitti EA. Urticaria. An Bras Dermatol. 2005;80:613-30. Recently some authors showed that the activated fraction of C5 complement, when bound to its receptor on the membrane of neutrophils, activate these cells and begin to express tissue factor in their cytoplasm membranes. Moreover, C5a can induce thrombosis by increasing TF expression on endothelial cells and monocytes in mice.1919. Muhlfelder TW, Niemetz J, Kreutzer D, Beebe D, Ward PA, Rosenfeld SI. C5 chemotactic fragment induces leukocyte production of tissue factor activity: a link between complement and coagulation. J Clin Invest. 1979;63:147-50. , 2020. Ikeda K, Nagasawa K, Horiuchi T, Tsuru T, Nishizaka H, Niho Y. C5a induces tissue factor activity on endothelial cells. Thromb Haemost. 1997;77:394-8. Ritis et al. reported the same results in humans.2121. 21.Ritis K, Doumas M, Mastellos D, Micheli A, Giaglis S, Magotti P, et al. A novel C5a receptor-tissue factor cross-talk in neutrophils links innate immunity to coagulation pathways. J Immunol. 2006;177:4794-802. The expression of tissue factor may activate the extrinsic pathway of coagulation, generating thrombin and fibrin, which, under fibrinolysis may produce D-dimer. Thus, this sequence of events may explain our findings of elevated d-dimer in plasma of patients with urticarial vasculitis during disease activity.
CONCLUSIONS
Patients with active chronic urticaria have higher serum levels of D-dimer when compared to patients with chronic urticaria under remission.
Patients with chronic urticaria under remission and patients with psoriasis, presented with normal serum levels of D-dimer.
Patients with urticarial vasculitis presented with elevated serum D-dimer levels, an indirect evidence of activation of blood coagulation cascade.
REFERENCES
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1Bindslev-Lensen C, Finzi A, Greaves M, Camarasa J, Ortonne JP, Schöpf E, et al. Chronic urticaria: diagnostic recommendations. J Eur Acad Dermatol. 2000; 14:175-80.
-
2Nettis E, Pannofino, Uappile C, Ferrannini A, Tursi A. Clinical and aetiological aspects in urticaria and angio-oedema. Br J Dermatol. 2003;148:501-6.
-
3Wisnieski JJ. Urticarial vasculitis. Curr Opin Rheumatol. 2000;12:24-31.
-
4Grattan C, Sabroe R, Greaves M. Chronic urticaria. J Am Acad Dermatol. 2002;46:645-57.
-
5Hein R. Chronic urticaria: impact of allergic inflammation. Allergy. 2002;57:S19-24.
-
6Zuberbier T, Henz B, Fiebiger E, Stingl M. Anti-FceRI serum autoantibodies in different subtypes of urticaria. Allergy. 2000;55:951-4.
-
7Sabroe RA, Fiebiger E, Francis DM, Maurer D, Seed PT, Grattan CE, et al. Classification of anti-FcepsilonRI and anti-IgE autoantibodies in chronic idiopathic urticaria and correlation with disease severity J Allergy Clin Immunol. 2002;110:492-9.
-
8Cugno M, Marzano AV, Asero R, Tedeschi A. Activation of blood coagulation in chronic urticaria: pathophysiological and clinical implications. Intern Emerg Med. 2010;5:97-101.
-
9Ver Elst K, Jochmans K, De Pauw A, De Waele M. Plasma D-dimer concentrations in different clinical conditions. Acta Clin Belg. 2002;57:325-30.
-
10Asero R, Tedeschi A, Cugno M. Heparin and tranexamic acid therapy may be effective treatment -resistant chronic urticarial with elevated D-dimer: a pilot sudy. Int Arch Allergy Inmunol. 2010;152:384-9.
-
11Asero R, Cugno M, Tedeschi A. Activation of blood coagulation in plasma from chronic urticaria patients with negative autologous plasma skin test. J Eur Acad Dermatol Venereol. 2011;25:201-5.
-
12Asero R, Tedeschi A, Coppola R, Griffini S, Paparella P, Riboldi P, et al. Activation of the tissue factor pathway of blood coagulation in patients with chronic urticaria. J Allergy Clin Immunol. 2007;119:705-10.
-
13Kasperska-Zajac A, Brzoza Z, Rogala B. Blood urokinase plasminogen activator system in chronic urticaria. Arch Dermatol Res. 2007;298:409-11.
-
14Breitenstein A, Camici GG, Tanner FC. Tissue factor: beyond coagulation in the cardiovascular system. Clin Sci (Lond). 2010;118:159-72.
-
15Dugina TN, kiseleva EV, Chistov IV, Umarova BA, Strukova SM. Receptors of the PAR family as a link between blood coagulation and inflammation. Biochemistry (Moscow). 2002;67:65-74.
-
16Osterud B. Tissue factor expression in blood cells. Thromb Res. 2010;125:S31-4.
-
17Mitroulis I, Kambas K, Anyfanti P, Doumas M, Ritis K. The multivalent activity of the tissue factor-thrombin pathway in thrombotic and non-thrombotic disorders as a target for therapeutic intervention. Expert Opin Ther Targets. 2011;15:75-89.
-
18Criado PR, Criado RFJ, Maruta CW, Martins JEC, Rivitti EA. Urticaria. An Bras Dermatol. 2005;80:613-30.
-
19Muhlfelder TW, Niemetz J, Kreutzer D, Beebe D, Ward PA, Rosenfeld SI. C5 chemotactic fragment induces leukocyte production of tissue factor activity: a link between complement and coagulation. J Clin Invest. 1979;63:147-50.
-
20Ikeda K, Nagasawa K, Horiuchi T, Tsuru T, Nishizaka H, Niho Y. C5a induces tissue factor activity on endothelial cells. Thromb Haemost. 1997;77:394-8.
-
2121.Ritis K, Doumas M, Mastellos D, Micheli A, Giaglis S, Magotti P, et al. A novel C5a receptor-tissue factor cross-talk in neutrophils links innate immunity to coagulation pathways. J Immunol. 2006;177:4794-802.
-
*
Work performed at the Ambulatório de Urticária da Divisão de Dermatologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HC-FMUSP) - São Paulo (SP), Brazil.
Publication Dates
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Publication in this collection
June 2013
History
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Received
06 Nov 2011 -
Accepted
04 Sept 2012