Antiphospholipid Antibody Syndrome. Rare Diseases of the Immune System

10. Non-Thrombotic Hematologic Manifestations in APS

Wilma Barcellini  and Carolina Artusi 

(1)

Anemia Physiopathology Unit, Onco-hematology Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, Milan, 20122, Italy

(2)

Division of Rheumatology – Istituto Ortopedico Gaetano Pini, Department of Clinical Sciences and Community Health, University of Milan, Milan, 20122, Italy

Wilma Barcellini (Corresponding author)

Email: wbarcel@policlinico.mi.it

Carolina Artusi

Email: carolina.artusi@unimi.it

Keywords

Immune thrombocytopeniaAutoimmune hemolytic anemiaNeutropenia

10.1 Introduction

Non-thrombotic hematologic manifestations have been largely reported in antiphospholipid syndrome (APS), although not included in the criteria for classification of this syndrome. The most common hematologic manifestation is thrombocytopenia, followed by hemolytic anemia and less frequently leukopenia [12]. The underlying pathophysiology of these cytopenias is usually thought to be mediated by autoimmune mechanisms, even if more recently other factors are under investigation. Consistent with the autoimmune genesis are the demonstration of antibodies directed against platelets, erythrocytes, or leukocytes and the finding of compensatory hyperplasia of the respective bone marrow precursors. However, the diagnosis of “true” autoimmune cytopenia may be cumbersome due to the heterogeneity and the low sensitivity of the different methods available for the detection of autoantibodies, particularly for platelets and leukocytes. In addition, it may be important to distinguish between mild cytopenias in the context of APS and primary immune thrombocytopenia (ITP), autoimmune hemolytic anemia (AIHA), and chronic idiopathic neutropenia (CIN) which may be definite diseases associated with APS

In this chapter, we will describe these hematologic abnormalities, both considering the context of APS and the hematologic point of view.

10.2 Thrombocytopenia

Thrombocytopenia, defined by a platelet count lower than 100 × 109/L [1], is reported in about 20–40 % of APS patients [35]. It is usually a chronic, mild form and is rarely associated with hemorrhagic complication [6]; in fact, most cases show platelets >50 × 109/L and only about 5–10 % platelets <50 × 109/L [7]. In the latter cases, bleeding manifestations may occur, although severe and life-threatening hemorrhages are reported for platelets <5–10 × 109/L. In the last years, there is accumulating evidence about the risk of hemorrhage and platelet count in ITP, where treatment is recommended for platelets <25–30 × 109/L. The different guidelines recommend that not only the “number” of platelets should be considered in the decision to treat but also age and lifestyle, comorbidities predisposing to bleeding, patient need for non-ITP medications that may create a bleeding risk, and surgery potentially causing major bleeding [810]. For example, a “safe” platelet count, in the absence of other risk factors for bleeding, was reported as ≥30 × 109/L for simple dental extractions or low-risk procedures (bronchoscopy and endoscopy); ≥50 × 109/L for complex dental extraction, biopsy of soft tissues, or minor surgery; ≥80 × 109/L for major surgery; and ≥100 × 109/L for neurosurgery, including epidural or spinal puncture [8]. Finally, it is worth underlining that patients with chronic thrombocytopenia are ~4- to 5-fold at risk for hemorrhage compared with the general population, but also ~4- to 5-fold at risk for infections, so that bleeding and infection contribute equally to mortality [11]. Moreover, there is emerging evidence that the thrombotic risk is increased in ITP, even at platelet count where the concern of the general practitioner is bleeding [1213]. This increased risk has also been attributed to the presence of antiphospholipid (aPL) antibodies, together with conventional prothrombotic risk factors (diabetes, hypertension, old age). Kim et al. [14] reported that 12.7 % of patients with ITP experienced a thromboembolic event (both arterial and venous), with a cumulative incidence rate ratio of 3.15 (95 % CI 1.21–8.17) in aPL antibodies-positive versus aPL antibodies-negative cases, after adjusting for age, hypertension, diabetes, dyslipidemia, smoking, and pregnancy/puerperium; moreover, hypertension and the presence of lupus anticoagulant (LA) emerged as independent risk factor for thrombosis.

10.2.1 Pathogenesis

The pathogenesis of thrombocytopenia in APS is not fully understood. There is a proposed role for aPL antibodies which can directly bind to platelet membrane anionic phospholipids, usually hidden in the inner membrane leaflet but exposed after activation [15]. Currently, there is a general agreement that aPL antibodies react with beta2 glycoprotein, which is a cationic protein that binds to negatively charged phospholipids exposed by activated platelets; consistently, it was demonstrated that aPL do not react with resting platelets [16].

Other studies have focused on antibodies directed against platelet glycoproteins (GP) IIb–IIIa and/or GPIb–IX, usually detected in 20–50 % of primary ITP by various techniques (ELISA, modified antigen-capture ELISA, flow cytometry, and immunoblot) [1719]. These antibodies have been detected in 40 % of cases positive for aPL antibodies [1718] and in a fraction of small series of patients with aPL antibodies and thrombocytopenia [20]. On the other hand, aPL antibodies have been detected in primary ITP: aCL antibodies in 25–30 % [21], LA or aCL antibodies in 46 %, and both LA and aCL antibodies in 16 % [22]. More recently, a prospective study showed that 38 % of ITP patients were aPL antibodies positive at diagnosis and that half of them developed clinical features of APS after a median of 38 months [23]. These findings suggest that there is an overlapping pathogenic role for anti-GP and aPL antibodies in ITP and APS, although the former seem to have a major role. Of note, in ITP, it is well established that antibody-coupled platelets are removed by macrophages via FCγ receptors in the reticular endothelial system and spleen [24]. However, there is emerging evidence that antibodies react against bone marrow megakaryocytes, leading to apoptosis and therefore inadequate compensatory hematopoiesis. This mechanism of immune cytopenia has been hypothesized also for other autoimmune diseases, such as SLE [25].

10.2.2 Diagnosis

The diagnosis of thrombocytopenia in the context of the APS is usually simple, as it is based on the presence of platelets <100 × 109/L. The diagnostic scenario is more complicated in patients with isolated aPL antibodies positivity and thrombocytopenia. In these cases, the diagnosis of ITP should be considered, according to the diagnostic workup proposed in the recently published guidelines [81026]. In fact, ITP is a diagnosis made after the exclusion of infectious (particularly Helicobacter pylori), liver, bone marrow, drug-associated, and inherited thrombocytopenias, since no “gold standard” test can reliably establish the diagnosis; even the test for antibodies directed against platelet GPIIb–IIIa and/or GPIb–IX is considered of potential utility only [26].

10.2.3 Therapy

Treatment of thrombocytopenia in the context of APS depends on clinical manifestations, serologic profile, comorbidities, and other thrombotic risk factors. While therapy for patients with an established ITP diagnosis is quite well defined, the treatment in case of aPL antibodies positivity in patients asymptomatic or with non-classification criteria is still a matter of debate. In the recent years, various guidelines have been published for the treatment of ITP, which usually starts at platelet values 25–30 × 109/L, provided that no other bleeding factors are present [81026]. This is of particular importance in APS patients, since aspirin and anticoagulants are frequent concurrent medications. In fact, a long-term oral anticoagulant therapy is suggested for APS patients with history of thrombosis [2728], and obstetric APS patients should be treated with low-dose aspirin associated to prophylactic dosage of low molecular weight heparin, increased at full therapeutic dose in case of previous thromboembolic events [27]. In these cases, treatment of thrombocytopenia should be considered at platelet count above the “classic” threshold, although it is not proven by a definite clinical study ad hoc: in the clinical practice, a platelet value of 50–60 × 109/L is considered “safe” enough to administer concurrent anticoagulant or antiaggregant therapy, and 90–100 × 109/L is required for double antiaggregant; finally, anticoagulation and antiaggregation with platelets <20 × 109/L require carefully discussion of pros and cons in the particular clinical context [29].

First-line treatment of ITP usually includes steroids alone or in combination with intravenous immunoglobulins (IVIG). Steroids may be administered orally (prednisone 1 mg/kg/day for 21 days then tapered off over a period of 3–4 months) or, in particularly severe cases, as intravenous bolus (methylprednisolone 5–10 mg/kg/day for 3–5 days, followed by oral prednisone). Recently, high-dose dexamethasone (40 mg/day for 4 days, for 4–6 cycles every 14 days) was proven effective as standard prednisone (about 80–85 % responses), with possible lower side effects [3031]. However, looking forward for ongoing randomized controlled studies aimed to demonstrate the better first-line steroid regimen, the current guidelines recommend longer rather than shorter courses of corticosteroids, because the former are associated with a better sustained response.

Regarding IVIG, their use is recommended in association to steroids for severe cases, in steroid-refractory patients, and as first line before steroids when the latter are clearly contraindicated. The most common regimens are 0.4 g/kg/day for 5 days or 1 g/kg for 1–2 days, the former being the more used and the latter recommended by the guidelines. It is worth reminding that platelet transfusion should never be denied in the presence of major hemorrhagic diathesis. Of note, the clinical practice is different in APS-associated ITP, where immunosuppressors such as azathioprine are given as steroid-sparing agents even as first-line treatment and IGIV are used as second-line treatment. Moreover, hydroxychloroquine is increasingly used in APS-associated ITP for its anti-inflammatory and antithrombotic properties and ability to reduce the expression of GpIIb/IIIa on activated platelets [3233]. On the contrary, in primary ITP, there is no clear recommendation about the sequence of second-line treatments, i.e., splenectomy, rituximab, immunosuppressors, and thrombopoietin (TPO) agonists. The guidelines for primary ITP recommend that the choice among various options should be individualized, and patient participation in decision-making should be paramount [826]. Splenectomy provides the highest cure rate (60–70 % of primary ITP patients at 5 years) but is invasive, irreversible, and associated with postoperative complications and its outcome is currently unpredictable [81026]. In APS-associated ITP, the outcome after splenectomy is even more controversial, both poor and good responses being seldom reported [2734]. Moreover, the increased rate of thrombotic events reported after splenectomy may further discourage this treatment option in APS [28].

Rituximab (375 mg m2/weekly × 4 weeks) was reported effective in about 50–60 % of primary ITP cases, with 20 % sustained responses at 5 years; it is generally well tolerated, and its short-term toxicity is acceptable [826]. TPO agonists induce platelet count >50 × 109/L in 90 % of adults with primary ITP, are well tolerated and show relatively little short-term toxicity, but need continuous administration [826] and no data are available in APS-associated ITP.

The guidelines for primary ITP conclude that at one end of the spectrum, splenectomy may be the preferred option for younger patients, who have the best response and lowest complication rates; at the other end of the spectrum, splenectomy is not recommended in patients over 65–70 years of age because of higher complications and lower response rates, and in very frail cases, with significant surgical comorbidities, and history or risk of thrombosis. The latter should be kept in mind because abnormal elevation of platelet count and thrombotic events are increasingly reported in patients treated with TPO agonists [10].

The most common treatment options for primary ITP are shown in Table 10.1.

Table 10.1

Most common treatment options for primary ITP

 

Treatment

Response rate

Sustained response

First-line therapy

Corticosteroids

~70–85 %

20–30 %

 Prednisone 1 mg/kg/day p.o.

 Methylprednisolone i.v. 5–10 mg/kg/day for 3–5 days

 High-dose dexamethasone 40 mg/day for 4 days for 4–6 cycles every 14 days

IVIG

>80 % transient responses

Poor evidence

Further lines of therapy

Immunosuppressive drugs (azathioprine, cyclophosphamide, cyclosporine)

~40–60 %

Not available

Rituximab standard dose (375 mg/m2/week × 4 weeks)

~50–60 %

20 % at 5 years

Splenectomy

~80 %

60–70 % at 5 years

Thrombopoietin agonists

~90 %

Not available

10.3 Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) was reported to occur in about 10 % of APS patients belonging to a large cohort of 1,000 patients [1]. Moreover, several studies report high frequencies of positive direct antiglobulin test (DAT) or Coombs test in patients with SLE-associated APS. A significant association between AIHA and the presence of aCL IgG was reported in 41 patients affected by SLE [35] and later confirmed in a larger retrospective study including 305 SLE patients [36]. Furthermore, aCL antibodies were found in eluates from erythrocytes of patients with AIHA and positivity for aCL antibodies [37], and anti-red cell binding activity present in eluates can be inhibited by absorption on phospholipid micelles [38]. More recently, the associations between AIHA and various manifestations of APS were evaluated in 308 patients with APS, confirming a prevalence of AIHA of 10.4 % [39]. The authors found that odds ratio for AIHA was increased in the presence of aCL antibodies and livedo reticularis and that AIHA was associated with cardiac valvular vegetations and thickening, arterial thrombosis, and CNS signs of epilepsy or chorea; in addition, AIHA may identify a subgroup of patients with a significant risk for subsequent development of SLE. Moreover, AIHA at the onset of SLE was independently associated with renal involvement, thrombocytopenia, and possibly thrombotic episodes during follow-up [35].

On the other hand, patients with AIHA, both idiopathic and associated with SLE, displayed higher titers of aCL antibodies [40]. The role of aPL antibodies with regard to the reported thromboembolic risk of AIHA has been investigated [4143]. In particular, Pullarkat et al. [41] reported venous thromboembolic events in 27 % of AIHA patients and detected aPL antibodies in 63 % of them, of whom 30 % had a lupus anticoagulant and 57 % aCL antibodies. There was a statistically significant association between presence of LA and occurrence of venous thromboembolic events. The target red cell antigen of aCL antibodies on red cells is still undefined: since cardiolipin is not present in the inner leaflet of erythrocytes, some authors have hypothesized a cross reactivity against negatively charged phospholipids (such as phosphatidylcholine) [43].

Clinically, AIHA may develop gradually, with concomitant physiologic compensation, or may have a fulminant presentation with rapid onset of profound, life-threatening anemia. Clinical features are determined by the rate and type of hemolysis, which mainly depend on the autoantibody’s characteristics (Ig class, thermal amplitude, affinity, efficiency in activating complement) and on the efficacy of the erythroblastic response. In particular, cases with reticulocytopenia are often more severe and require high transfusion support; in these cases, an anti-erythroblast reactivity has been hypothesized to occur, with consequent intramedullary death or apoptosis of red cell precursors [44].

10.3.1 Diagnosis

The diagnosis of AIHA is based on the presence of hemolytic anemia and serologic evidence of anti-erythrocyte autoantibodies, detected by the DAT, and identified in the serum and/or eluate obtained from the patient’s red blood cells (RBCs) [44]. DAT tube, the traditional agglutination technique, is usually performed with broad-spectrum Coombs reagents. Clinically, it is important to perform the test with monospecific antisera, to distinguish “warm” (WAIHA), “cold” (cold hemoagglutinin disease, CHD), and “mixed” forms. The former are due to IgG which generally react at 37 °C, are usually directed against epitopes of the Rh system, and mainly determine extravascular hemolysis. Cold forms are due to IgM, which are able to fix complement more efficiently than other isotypes, have an optimal temperature of reaction at 4 °C, are directed against the I/i system, and prevalently cause intravascular hemolysis. The presence of cold IgM autoantibodies can easily be revealed by the spontaneous agglutination of RBCs at 20 °C. It should be reminded that there are rare cases of warm AIHA caused by IgM “warm” autoantibodies that have more severe hemolysis and more fatalities than patients with other types of AIHA. This may be related to the amount of RBC destruction by intravascular hemolysis, calculated in 200 mL of RBCs in one hour, versus extravascular hemolysis which is 10-fold lesser [44].

It is important to remind that DAT with polyspecific or anti-IgG and anti-C antisera may yield false-negative results due to the presence of IgA, low-affinity autoantibodies, or numbers of RBC-bound IgG molecules below the threshold of the test (400 molecules per RBC). For the former two conditions, the use of monospecific antisera against IgA and low ionic strength solutions (LISS) or cold washings can overcome the DAT negativity; small amounts of RBC-bound IgG can be detected employing more sensitive but less specific techniques, such as microcolumn and solid-phase antiglobulin tests that are suitable for automation, or other more sophisticated techniques, such as the complement fixation antibody consumption test, the enzyme-linked and radiolabeled tests, and the flow cytometry, that are not routine in the majority of laboratories. The latter deserves a particular mention because of its high sensitivity, being able to detect up to 30–40 molecules of anti-RBC autoantibodies. Finally, the mitogen-stimulated (MS) DAT has been proposed as a functional and quantitative method for the detection of anti-RBC antibodies in mitogen-stimulated whole-blood cultures, which may facilitate the diagnosis of some DAT-negative AIHA cases [45].

Despite the numerous tests available for the detection of antibodies against RBCs, and the development of additional more sensitive techniques, about 10 % of AIHA remains DAT negative, and the diagnosis is made after exclusion of other causes of hemolysis and on the basis of the clinical response to therapy [44].

It is worth reminding that DAT positivity may be due not only to autoantibodies, but also to alloantibodies, possibly present in transfused subjects and in multiparous females, and responsible severe hemolytic reactions in case of RBC transfusion. Moreover, false-positive DAT have been reported in patients with hypergammaglobulinaemia or following high-dose immunoglobulin therapy [46]. Finally, 0.007–0.1 % of the healthy population and 0.3–8 % of hospitalized patients have a positive DAT without AIHA.

10.3.2 Treatment

The treatment of AIHA is still not evidence based as there are no randomized studies and only a few prospective phase 2 trials. Conventional therapy of WAIHA includes administration of corticosteroids as first-line therapy, which is expected to provide a response in 70–80 % of patients. Second-line therapy for APS-associated AIHA is mainly represented by immunosuppressive agents, such as azathioprine, cyclophosphamide, and cyclosporine, which generally provide a 40–60 % response rate. There is growing interest in the use of mycophenolate mofetil in patients with warm AIHA, particularly children; although limited to small series of patients, good responses are reported in almost all cases both idiopathic and secondary to SLE [4748]. More recently, rituximab (375 mg m2/weekly  × 4 weeks) has been shown to be effective in about 60–80 % of cases, either in monotherapy or in combination with corticosteroids and immunosuppressors, and regardless of prior therapy. The time to response varies considerably, with some patients responding very quickly and others taking weeks or even months to achieve their maximum response. Finally, rituximab re-treatment may be effective, and some patients responded to re-treatment more than once [49]. In attempt to minimize side effects and reduce costs, first-line treatment with low-dose rituximab (100 mg fixed dose × 4 weeks) plus a short course of steroids was reported equally effective as standard doses, with an overall response in 89 % (complete response 67 %) and 68 % relapse-free survival at 3 years [5051].

IVIG are frequently used in AIHA, alone or in combination with prednisone, probably because of their proven effectiveness in primary ITP and the relatively low incidence of adverse effects. However, only small case series have been reported [4452], and the only large retrospective study of 73 patients [53] showed a response in 40 % of cases, only 15 % achieving hemoglobin levels of 10 g/dL or greater.

It is noteworthy that steroids are poorly useful in cold forms, whereas rituximab is able to induce a complete response in 10–15 % and a partial in 50 % of patients; this compares favorably with the next best treatment regimens which give about 15–20 % of partial responses [5456]. Recently, fludarabine-rituximab combination therapy was reported very effective, resulting in 75 % response rate, complete remissions in about 20 %, and more than 66 months estimated response duration [57].

The effectiveness of other options, such as plasmapheresis and danazol, is controversial and mostly anecdotal [5455]. High-dose cyclophosphamide was effective in 4/5 patients, all of whom were previously treated with corticosteroids [58]. Other “last option” treatments include alemtuzumab, bortezomib, and eculizumab which have been shown to be of some efficacy in few cases [545961]. Moreover, the administration of erythropoietin was successfully used in patients with therapy-refractory AIHA, particularly in the presence of reticulocytopenia [62]. Finally, both autologous and allogenic bone marrow transplantation were reported in immune cytopenias, including severe AIHA and Evans syndrome [63].

Splenectomy, although not performed in APS-associated cytopenias, is considered the most effective second-line treatment for primary warm AIHA, with early responses in around 70 % of cases and persistent remissions without need of medical intervention for years [54].

The most common treatment options for idiopathic AIHA are shown in Table 10.2.

Table 10.2

Most common treatment options for idiopathic AIHA

 

Treatment

Response rate

Sustained response

First line therapy

Corticosteroids (prednisone 1 mg/kg/day p.o.)

~70–80 % in WAIHA

30 % once the drug is discontinued, 40–50 % require maintenance doses, 20–30 % need additional second-line therapies

~20 % in CHD

Further lines of therapy

Immunosuppressive drugs (azathioprine, cyclophosphamide, cyclosporine)

~40–60 %

Not available

Rituximab standard dose (375 mg/m2/week × 4 weeks)

~60–80 % in WAIHA

>3 years in some cases

Rituximab low dose (100 mg/week × 4 weeks)

~15 % CR, 50 % PR in CHD

~70 % at 2 and 3 years (similar for WAIHA and CHD)

 

100 % WAIHA, 60 % CHD

Splenectomy

~70 % in WAIHA ineffective in CHD

20–60 % at 4–7 years

WAIHA warm autoimmune hemolytic anemia, CHD cold hemoagglutinin disease, CR complete response (Hb ≥ 12 g/dL and normalization of all hemolytic markers), PR partial response (Hb ≥ 10 g/dL or at least 2 g/dL increase in hemoglobin, and no transfusion requirement)

10.4 Leukopenia

It is known that antibodies anti-beta2-GPI may bind neutrophils [64]; however, the association between leukopenia and aPL antibodies is reported only in few studies. Cervera et al. analyzed the clinical and immunologic manifestations of APS in a cohort of 100 patients and reported that patients with APS secondary to SLE more frequently exhibited neutropenia than primary APS patients (38 % versus 2 %) [65]. This finding was confirmed by Vienna et al. [66] in a subsequent study on 56 patients with APS plus SLE and 58 with APS. At variance, in both studies, lymphopenia does not correlate with aPL antibodies. These data suggest that in these patients, neutropenia is due to other factors involved in the pathogenesis of SLE, rather than to the direct role of aPL antibodies.

Recently, we prospectively studied 56 adult patients with idiopathic neutropenia (manuscript submitted) to investigate the incidence of infections and the risk of evolution in hematologic malignancies. Results showed that neutropenia was mild in 35 patients (median 1.36 × 103/μL), moderate in 14 (median 0.49 × 103/μL), and severe in 7 (median 0.3 × 103/μL); monocytosis was observed in 10 patients, lymphocytosis in 5, and MGUS in 6; antineutrophil antibodies were positive in 19 cases, and splenomegaly was found in 11. During the 4-years follow-up, mean neutrophils were stably under the normal range, with a great intersubject variability but without significant intra-subject variations. Mean neutrophils were lower in patients with antineutrophil antibodies, in males, and in cases with MGUS. A grade 2 infection occurred in 13 patients without relationship with neutrophil values. Eleven patients evolved into chronic NK expansion (N = 4), hairy cell leukemia (N = 4), and myelodysplasia (1 chronic myelomonocytic leukemia, 1 refractory cytopenia with unilineage dysplasia, and 1 with multilineage dysplasia). The median time to the evolution was 30 months. These data suggest that idiopathic neutropenia in adults is a benign disease without occurrence of severe infections, despite the concern of the general practitioner. However, a hematologic follow-up is advisable considering the possible evolution into clonal hematologic diseases.

10.5 Conclusions

Non-thrombotic hematologic manifestations have been largely reported in APS and are caused by antibodies directed against blood cells. Among them, thrombocytopenia is the most frequent, followed by autoimmune hemolytic anemia and few cases of leukopenia/neutropenia. Most information on these cytopenias come from primary ITP guidelines and studies on idiopathic forms of AIHA and neutropenia that should be put into the context of APS. Several diagnostic aspects are important, such as the distinction between warm and cold AIHA forms, which has therapeutic implications. For mild forms, which are the most frequent ones, treatment is simple and effective and mostly based on drugs that are already used in APS or SLE, such as steroids, IVIG, immunosuppressors, and rituximab. However, for severe and refractory cases of these largely heterogeneous diseases, a particular experienced attention by clinicians is required, and a tight and constructive collaboration with hematologists is advisable.

Take Home Messages

·               Thrombocytopenia (platelets <100 × 109/L) is the most frequent hematologic manifestation of APS (20–40 % of cases) and is generally mild and without hemorrhagic manifestations, in contrast with primary immune thrombocytopenia (ITP).

·               No specific treatment for ITP is generally required for platelets >25–30 × 109/L.

·               Steroid-refractory ITP in the context of APS is mostly treated with immunosuppressors and poorly responsive to splenectomy, at variance with primary ITP.

·               Autoimmune hemolytic anemia (AIHA) occurs in about 10 % of APS patients and it is particularly heterogeneous from a clinical point of view.

·               Warm (direct antiglobulin test + for IgG) and cold forms (IgM, C) of AIHA have different responses to available treatments.

·               Both primary ITP and AIHA display a thrombotic diathesis, which should be carefully considered in the context of APS.

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