Significance Of Antiphospholipid Antibodies Research Articles

WCN23-0887 Prevalence and Clinical Significance of Anti Phospholipid Antibodies in Biopsy Proven Lupus Nephritis Patients in a suburban tertiary care center - An Interim Analysis

WCN23-0887 Prevalence and Clinical Significance of Anti Phospholipid Antibodies in Biopsy Proven Lupus Nephritis Patients in a suburban tertiary care center - An Interim Analysis

The impact of antiphospholipid antibodies in Takayasu arteritis.

The significance of antiphospholipid antibodies (aPL) is controversial in Takayasu arteritis (TA). This study was conducted to explore the frequency of aPL and their association with disease-related complications in TA. : This cross-sectional study was conducted to investigate the presence of anti-cardiolipin (aCL), anti-beta 2 glycoprotein- 1(aβ2G1) antibodies, and lupus anticoagulant (LA) in TA patients. TA patients admitted to the Department of Rheumatology of Hacettepe University Faculty of Medicine between December 2015 and September 2016 who fulfilled the American College of Rheumatology (ACR) classification criteria for TA were consecutively enrolled in the study. Patients were grouped according to aPL positivity and compared in terms of disease manifestations, type of vascular involvement at diagnosis, and vascular complications/interventions attributable to TA. Fifty-three TA (49 female) patients were enrolled in the study. We detected 9 (16.9%) patients with IgM and/or IgG aβ2G1 and/or LA positivity. There were no patients with positive aCL. All aβ2G1 titers were low. There were no differences in terms of symptoms, signs, type of vascular involvement, the number of patients with disease-related complications or vascular interventions/surgery between aPL (+) and aPL(-) groups (p > 0.05 for all). The number of patients with thrombotic lesions was similar between the groups (p > 0.05). There were no patients with a history of venous thrombosis or on anticoagulant treatment in the aPL(+) group. Only 1 patient with IgM aβ2G1 (+) had a history of pregnancy loss. Our results indicate that aPL positivity is not rare in TA. On the other hand, all aPL titers were low and no differences were found in the frequency of disease-related complications between aPL(+) and aPL(-) patient groups. Only TA patients with atypical manifestations with high suspicion of aPL-related complications should be considered to be investigated for aPL.

Pathogenetic significance of antiphospholipid antibodies in the development of placenta-associated complications in pregnant women with thrombocytopenia

BACKGROUND: Thrombocytopenia is one of the most common cytopenic syndromes that complicate pregnancy. It is considered a typical hematological criterion and the second most common manifestation of antiphospholipid syndrome. In recent years, the relationship between the development of thrombotic and placenta-associated pregnancy complications and the circulation of antiphospholipid antibodies has been actively studied, which makes it necessary to search for new methods for hemostasis correction and for prevention of the development of obstetric complications.
 AIM: The aim of this study was to assess the incidence of antiphospholipid antibodies in pregnant women with thrombocytopenia in order to determine the risk of obstetric complications and adverse pregnancy outcomes depending on the presence of antiphospholipid antibodies in the examined women.
 MATERIALS AND METHODS: 299 pregnant women were included in this multicenter prospective study: the main study group (n = 249) consisted of patients with thrombocytopenia, and the control group (n = 50) comprised women with normal platelet counts during a physiological pregnancy. All participants underwent a complete clinical and anamnestic examination and a study of the hemostasis system. To determine antibodies to cardiolipin, beta-2 glycoprotein 1, annexin V, and prothrombin (IgG/IgM/IgA), we performed enzyme-linked immunosorbent assay in 84 pregnant women with thrombocytopenia and in 25 women in the control group. Lupus anticoagulant was determined in 123 pregnant women of the main group and 25 women in the control group using an ACL-200 coagulometer (Instrumentation Laboratory, Spain).
 RESULTS: A comparative analysis of antiphospholipid antibodies detection has shown that in pregnant women with thrombocytopenia, lupus anticoagulant was detected in every third case (35.8% of cases, 44/123 women), which is more common than in the control group (8.0% of cases, 2/25 women; p = 0.008). Antibodies to beta-2 glycoprotein 1 were detected in pregnant women with thrombocytopenia in every fourth case (27.4% of cases, 23/84 women), and in the control group only in 4% of cases (1/25 women; p = 0.013). Antibodies to cardiolipin were also more often detected in pregnant women with thrombocytopenia (23.8% of cases, 20/84 women) compared to the control group (4% of cases, 1/25 women; p = 0.040). Based on the data obtained with V Cramer, we established medium-strength direct correlations between criterial antiphospholipid antibodies circulation and the development of placenta-associated complications of pregnancy (p 0.05; 0.2 V 0.4). We also identified statistically significant risks of developing placenta-associated complications in pregnant women with circulating antiphospholipid antibodies (95 % confidence interval excludes 1).
 CONCLUSIONS: Thrombocytopenia during pregnancy develops more often in women with antiphospholipid antibodies. Antiphospholipid antibodies circulation elevates coagulation potential and activates intravascular coagulation, resulting in an increased risk of placenta-associated complications of pregnancy, which requires hemostasis correction.

Prevalence and clinical significance of antiphospholipid antibodies in patients with coronavirus disease 2019 admitted to intensive care units: a prospective observational study

Coronavirus disease 2019 (COVID-19) increases the risk of coagulopathy. Although the presence of antiphospholipid antibodies (aPLs) has been proposed as a possible mechanism of COVID-19-induced coagulopathy, its clinical significance remains uncertain. Therefore, this study aimed to evaluate the prevalence and clinical significance of aPLs among critically ill patients with COVID-19. This prospective observational study included 60 patients with COVID-19 admitted to intensive care units (ICU). The study outcomes included prevalence of aPLs, and a primary composite outcome of all-cause mortality and arterial or venous thrombosis between antiphospholipid-positive and antiphospholipid-negative patients during their ICU stay. Multiple logistic regression was used to assess the influence of aPLs on the primary composite outcome of mortality and thrombosis. A total of 60 critically ill patients were enrolled. Among them, 57 (95%) were men, with a mean age of 52.8 ± 12.2 years, and the majority were from Asia (68%). Twenty-two patients (37%) were found be antiphospholipid-positive; 21 of them were positive for lupus anticoagulant, whereas one patient was positive for anti-β2-glycoprotein IgG/IgM. The composite outcome of mortality and thrombosis during their ICU stay did not differ between antiphospholipid-positive and antiphospholipid-negative patients (4 [18%] vs. 6 [16%], adjusted odds ratio 0.98, 95% confidence interval 0.1–6.7; p value = 0.986). The presence of aPLs does not seem to affect the outcomes of critically ill patients with COVID-19 in terms of all-cause mortality and thrombosis. Therefore, clinicians may not screen critically ill patients with COVID-19 for aPLs unless deemed clinically appropriate.

Antiphospholipid Antibodies in Patients with Membranous Nephropathy

Background/Aim: The aim of this study was to investigate the prevalence and significance of antiphospholipid antibodies in patients with membranous nephropathy (MN). Methods: Patients hospitalized with MN during June 2015 to June 2017 were selected and patients with minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS) in the same period were selected as controls. Results: Overall, 267 patients with MN and 131 patients with MCD/FSGS (n = 101 MCD and n = 30 FSGS) were analyzed. There was a significant difference in the detection rate of anti-β2-glycoprotein I (anti-β2-GPI) antibodies (11.9% in MN vs. 4.5% in MCD/FSGS, p = 0.018) and IgG-anti-β2-GPI antibodies (3.7% in MN vs. 0% in MCD/FSGS, p = 0.034) between the 2 groups. Anti-β2-GPI antibody-positive MN patients (n = 32) had a lower serum C4 level than anti-β2-GPI antibody-negative MN patients (n = 235; 21.6 ± 7.6 vs. 24.6 ± 7.1 mg/dL, p = 0.030). Anti-β2-GPI antibody-positive MN patients had significant improvement of serum creatinine compared to anti-β2-GPI antibody-negative patients after 24 weeks of treatment (p = 0.006). Conclusions: Anti-β2-GPI antibody may play a role in the progression of MN, and this process might involve classic complement activation.

Significance of Antiphospholipid Antibodies in Essential Cryoglobulinemia: A Case Report and Review of Literature

Significance of Antiphospholipid Antibodies in Essential Cryoglobulinemia: A Case Report and Review of Literature

Prevalence, significance and predictive value of antiphospholipid antibodies in Crohn's disease.

To assess the prevalence and stability of different antiphospholipid antibodies (APLAs) and their association with disease phenotype and progression in inflammatory bowel diseases (IBD) patients. About 458 consecutive patients [Crohn's disease (CD): 271 and ulcerative colitis (UC): 187] were enrolled into a follow-up cohort study in a tertiary IBD referral center in Hungary. Detailed clinical phenotypes were determined at enrollment by reviewing the patients' medical charts. Disease activity, medical treatment and data about evolvement of complications or surgical interventions were determined prospectively during the follow-up. Disease course (development f complicated disease phenotype and need for surgery), occurrence of thrombotic events, actual state of disease activity according to clinical, laboratory and endoscopic scores and accurate treatment regime were recorded during the follow-up, (median, 57.4 and 61.6 mo for CD and UC). Sera of IBD patients and 103 healthy controls (HC) were tested on individual anti-β2-Glycoprotein-I (anti-β2-GPI IgA/M/G), anti-cardiolipin (ACA IgA/M/G) and anti-phosphatidylserine/prothrombin (anti-PS/PT IgA/M/G) antibodies and also anti-Saccharomyces cerevisiae antibodies (ASCA IgA/G) by enzyme-linked immunosorbent assay (ELISA). In a subgroup of CD (n = 198) and UC patients (n = 103), obtaining consecutive samples over various arbitrary time-points during the disease course, we evaluated the intraindividual stability of the APLA status. Additionally, we provide an overview of studies, performed so far, in which significance of APLAs in IBD were assessed. Patients with CD had significantly higher prevalence of both ACA (23.4%) and anti-PS/PT (20.4%) antibodies than UC (4.8%, P < 0.0001 and 10.2%, P = 0.004) and HC (2.9%, P < 0.0001 and 15.5%, P = NS). No difference was found for the prevalence of anti-β2-GPI between different groups (7.2%-9.7%). In CD, no association was found between APLA and ASCA status of the patients. Occurrence of anti-β2-GPI, ACA and anti-PS/PT was not different between the group of patients with active vs inactive disease state according to appropriate clinical, laboratory and endoscopic scores in CD as well as in UC patients. All subtypes of anti-β2-GPI and ACA IgM status were found to be very stable over time, in contrast ACA IgG and even more ACA IgA status showed significant intraindividual changes. Changes in antibody status were more remarkable in CD than UC (ACA IgA: 49.9% vs 23.3% and ACA IgG: 21.2% vs 5.8%). Interestingly, 59.1% and 30.1% of CD patients who received anti-TNF therapy showed significant negative to positive changes in ACA IgA and IgG antibody status respectively. APLA status was not associated with the clinical phenotype at diagnosis or during follow-up, medical therapy, or thrombotic events and it was not associated with the probability of developing complicated disease phenotype or surgery in a Kaplan-Meier analysis. The present study demonstrated enhanced formation of APLAs in CD patients. However, presence of different APLAs were not associated with the clinical phenotype or disease course.

The Significance of Antiphospholipid Antibodies in Liver Recipients

BackgroundThe presence of antiphospholipid antibodies (APLAs) may be associated with increased thrombotic risk. Liver graft thrombosis may necessitate retransplantation. AimTo determine the prevalence of APLAs among liver recipients and to investigate the relationship between APLAs and liver graft thrombosis. Materials and methodsWe included 33 Caucasian patients aged 22 to 75 years who displayed stable liver graft function (21 women and 12 men). The patients were divided into 2 subgroups: high thrombotic risk subgroup T(−) and at low risk T(+) subgroups. The T(−) included 25 patients, T(+) included 8 recipients with a history of severe thrombosis. We investigated: lupus anticoagulant, anticardiolipin antibodies (aCL), anti-β2-glycoprotein I antibodies (anti-β2GPI), antiprothrombin antibodies (immunoglobulin (Ig)G and IgM isotype), protein C and S activities, factor VIII, antithrombin, ADAMTS-13 and anti-ADAMTS-13. The 2 determinations were performed at an interval of 6 months. The mean follow-up was 19.5 ± 4.6 months. ResultsThe most commonly detected antibodies were anti-β2GPI IgM (25%) and aCL IgG (15.63%). Comparing the prevalence of APLAs between T(−) and T(+), we observed a significant difference only for aCL IgM (P = .0183), which was not confirmed on a second determination after 6 months. We noted correlations between aCL IgM and number of thrombotic episodes (P = .0040) and between aCL IgM and anti-β2GPI IgM (P = .0074; rho 0.45). Despite receiving low-molecular-weight heparin or aspirin recurrence of thrombosis occurred in 4 T(+) patients: 3 hepatic artery thrombosis and 1 splenic artery thrombosis. Only 1 patient had APLAs; the other 2, protein C or S deficiency and the fourth, a normal test. ConclusionsThe prevalence of APLAs in liver recipients is greater than that in the general population. The usefulness of APLAs as a marker of thrombosis was not demonstrated suggesting multifactorial etiologies of liver graft thrombosis.

The Significance of Antiphospholipid Antibodies as a Marker of Thrombosis in Patients after Liver Transplantation - A Single Center Experience

The Significance of Antiphospholipid Antibodies as a Marker of Thrombosis in Patients after Liver Transplantation - A Single Center Experience

Clinical significance of antiphospholipid antibodies in Indian scleroderma patients

In patients with systemic sclerosis (SSc), antiphospholipid antibodies (aPL) have been reported to be associated with more severe manifestations including digital infarct, gangrene and pulmonary hypertension. But these findings are not consistent in all studies; moreover, there are no data available from Indian subcontinent. The objective of this study is to assess the prevalence of antiphospholipid antibodies in Indian SSc patients and correlate them with clinical and immunological features. Seventy-two patients were recruited prospectively from rheumatology clinic from 2002 to 2006. Their medical records were reviewed. Anticardiolipin antibodies (IgG, IgM) by ELISA and lupus anticoagulant (LA) were tested in standardized pattern and repeated after 6 weeks. Anti-β2 glycoprotein-I antibodies were done in patients who had aPL antibodies. Nineteen patients had diffuse cutaneous SSc and 53 had limited disease. Seven patients (9.7%) were positive for aPL antibodies in their sera. Only one patient had clinical features of antiphospholipid antibody syndrome and manifested with recurrent abortions and deep vein thrombosis. She was positive for aCL, LA and anti-β2 glycoprotein-I antibodies. Four patients were only aCL (IgG) positive in moderate titers and one each had only aCL (IgM) and LAC positivity. None of the clinical parameters showed an association with aPL antibody.

Prevalence and significance of antiphospholipid antibodies in selected at-risk obstetrics cases: A comparative prospective study

SummaryIn a prospective comparative study we screened 112 women with a past history either of pre-eclampsia, eclampsia, recurrent abortion, IUGR, IUFD or abruptio placentae, with no apparent aetiology and a demographically matched cohort of 106 women having a past history of uncomplicated pregnancy outcome for the presence of antiphospholipid antibodies (aPL) and their significance. In the former group, the prevalence of aPL ranged from 10–46.87% compared with 8.49% in the later group. In women with the presence of aPL, the incidence of pre-eclampsia, early onset pre-eclampsia and abruptio placentae were 25%, 14.58% and 18.75%, respectively. In the same group, the abortion rate was 25% and live-birth rate was 64.58% with IUFD rate of 10.42%. Fetal morbidity rates were also higher in the mothers with aPL positivity, the incidence of IUGR was 27.08% and oligohydramnios was 33.33% in them. All these complications were statistically significant when compared with those of aPL negative mothers.

In a Prospective Inceptional Cohort Study of Children with Thrombosis, a Persistently Positive Dilute Russell Viper Venom Time Is Associated with Thrombus Progression or Recurrence and Multiple Antiphospholipid Antibodies

BACKGROUND: Antiphospholipid antibodies (APA) that persist ≥12 weeks in adults with acute thrombosis are predictive of thrombus recurrence. The significance of APA in children with thrombosis is unclear. This study was developed to examine the relationship of a persistently positive lupus anticoagulant (≥ 12 weeks), assessed by the dilute Russell Viper Venom Time (dRVVT), to adverse thrombus outcomes including progression or recurrence. In addition, the relationship of a persistently positive dRVVT to the prevalence and titer of several other APA in children with thrombosis were examined.METHODS: Data from a consented prospective inceptional cohort study of pediatric thrombosis and thrombophilia (COMIRB 05–0339) were extracted for this analytic project. Eligibility included age ≤ 21 years at presentation, objectively confirmed thrombus, dRVVT within 4 weeks of presentation and repeated ≥ 12 weeks later. Patients with a persistently positive dRVVT (ratio of Screen/Confirm ≥1.2) were classified as having antiphospholipid syndrome (APS positive), and those with a negative dRVVT were classified as APS negative. Twelve or more weeks from presentation, patient plasmas were tested in ELISA assays for the presence and titer of IgM and IgG antibodies directed against protein C (PC), protein S (PS), prothrombin (II), β-2-Glycoprotein I (B2GPI), and cardiolipin (ACA). A euglobulin clot lysis assay (ELT) and hexagonal (II) phase phospholipid assay (STACLOT LA, Diagnostica Stago, Inc.) were also performed.RESULTS: The cohort included 122 cases with thrombosis. Of these, 35 failed eligibility due to transient dRVVT positivity or lack of blood sampling within the specified time period. Of the remaining 87 patients, 43 were APS positive and 44 were APS negative. APS positivity was associated with longer duration of therapy (p<0.001) and multiple autoantibodies at ≥ 12 weeks from presentation (p=0.04). APS was associated with higher titers of several antibodies, including those directed against: B2GPI (IgG, p=0.01), II (IgG, p=0.02), PC (IgG, p=0.03; IgM, p<0.001). Despite the longer duration of therapy for these patients, APS was highly associated with thrombus progression or recurrence (47% in APS positive versus 8% in APS negative, p=0.001). Thrombus progression or recurrence was further associated with positivity for ACA IgM, Anti-II IgM and the STACLOT LA (p=0.02 for each), and additionally with higher titers of antibodies against B2GPI (IgG, p=0.03), II (IgM, p=0.05), PC (IgM, p=0.04), and PS (IgM, p=0.03).CONCLUSION: In this pediatric prospective inceptional cohort study, APS (defined as a persistence of positive dRVVT 12 weeks or greater in children affected with thrombosis), was found in more than one third of children and was associated with higher prevalence and titers of several APA. In spite of longer duration of therapy, children with APS had a significantly higher rate of thrombus progression or recurrence. APA testing in children with thrombosis is important to predict outcomes. Future clinical trials must consider APS status in evaluating risk-stratified therapy for thrombotic diseases in children.

Significance of antiphospholipid antibodies in patients with bad obstetric history

Significance of antiphospholipid antibodies in patients with bad obstetric history

Anticuerpos antifosfolípidos en nefropatía membranosa idiopática

Antiphospholipid antibodies have been found in the sera from patients with idiopathic and secondary glomerulopathies, mainly related to lupus. No special attention has been devoted to idiopathic membranous nephropathy, a glomerular disease with a high frequency of thrombotic complications, particularly of the renal vein. To study the presence and significance of antiphospholipid antibodies in idiopathic membranous nephropathy. Anticardiolipin and anti-ss2-glycoprotein-I IgG antibodies were measured in serum samples from 21 patients with idiopathic membranous nephropathy (age range 11-75 years, 5 female). The medical records of 20 of these patients were reviewed, looking for vascular complications and nephrological evolution during a follow-up period that ranged from two to 277 months. Five patients had anticardiolipin antibody titers over the cutoff for normal values, and two others were positive for anti-ss2-glycoprotein-I, without cross-reactivity. There was no difference in the incidence of thrombotic complications in the renal vein, or other locations, between these seven patients and the remaining patients. No differences in the clinical course of the nephropathy were detected either. Antiphospholipid antibodies may be found in patients with primary membranous nephropathy. They are not related to thrombosis or a worse evolution.

Multiple sclerosis, neuropsychiatric lupus and antiphospholipid syndrome: where do we stand?

Multiple sclerosis (MS), systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) are chronic, immune-mediated, relapsing-remitting disorders affecting young adults, the pathogenesis of which is still largely unknown. Neurological manifestations and magnetic resonance imaging (MRI) can be indistinguishable and there are no specific diagnostic tools. Treatment and prognosis are quite different. There is controversy about the prevalence and significance of antiphospholipid antibodies (aPL) in MS. A significant number of patients with APS/SLE are misdiagnosed as MS but evidence suggests they are distinct nosological entities. However, it is essential to differentiate them since APS may be responsive to anticoagulation. When assessing MS patients, clinicians should consider APS/SLE, especially if the MS has atypical features. A trial of anticoagulation might be worthwhile in some patients with atypical MS and consistently positive aPL.

The significance of antiphospholipid antibodies in pregnant women with chronic hypertension.

The objective of this study was to perform antiphospholipid antibody screening in women with chronic hypertension to assess whether the presence of such antibodies is associated with adverse pregnancy outcome. Serum for anticardiolipin antibodies and lupus anticoagulant was obtained in pregnant women with chronic hypertension who had no other indications for such testing. The primary outcomes of interest were the development of superimposed preeclampsia, preterm delivery, and fetal growth restriction. Only 8 (9%) of the 87 women enrolled tested positive (> 95th percentile) for anticardiolipin immunoglobulin G. None tested positive for lupus anticoagulant. The presence of antiphospholipid antibodies was not associated with adverse pregnancy outcome. We were unable to demonstrate that screening for antiphospholipid antibodies is a useful clinical practice in women whose only pregnancy complication was chronic hypertension. The significance of such antibodies in this particular group of patients can only be resolved with a large multicenter study.

Clinical features of Behçet's disease in patients in the Sultanate of Oman; the significance of antiphospholipid antibodies?

The prevalence of symptoms in 34 Omani patients with Behcet's disease (BD) was: recurrent oral ulceration 100%, arthritis/arthralgia and genital ulceration 74% each, folliculitis 64%, neurological lesions 62%, retinal vasculitis 30%, iritis and hypopyon 26%, gastrointestinal lesions 12%, venous thrombosis and cardiovascular lesions 9% each, and pleuropulmonary lesions and epididymitis 6% each. Antiphospholipid (APL) antibodies (both anticardiolipin [ACAs] and anti-beta2 glycoprotein I [abeta2GPIs]) were present in 11/34 (32%) of the BD patients and in 54/73 (74%) of Omani patients with systemic lupus erythematosus (SLE) (chi2 = 21.2, P<0.001). In patients possessing APL antibodies, there was no significant difference in mean antibody levels between BD and SLE patients. IgM isotype antibodies, in the absence of IgG, were more prevalent in BD (5/11) than in SLE (10/54) patients (chi2 =3.8, P = 0.05). The frequency of organ involvement was similar in patients with and without APL antibodies (chi2 = 1.226, P > 0.05). This study fails to demonstrate a pathognomonic role for APL antibodies in BD.

Prevalence and clinical significance of antiphospholipid antibodies (APA) in viral chronic liver disease

Prevalence and clinical significance of antiphospholipid antibodies (APA) in viral chronic liver disease

The Clinical Significance of Antiphospholipid Antibodies

The antiphospholipid syndrome is defined as the association between the presence of antiphospholipid antibodies, detected as anticardiolipin antibodies and/or lupus anticoagulant, and a history of either arterial or venous thrombosis and/or recurrent pregnancy loss. Because thrombosis may occur in virtually any organ system, diagnosing the antiphospholipid syndrome and taking appropriate anticoagulation measures are important considerations in all medical specialties. Antiphospholipid antibody-associated thrombosis tends to recur. Antithrombotic prophylaxis to prevent recurrences is therefore needed. Prophylaxis in individuals with circulating antiphospholipid antibodies who have no history of thrombosis is still controversial. Although direct evidence for a pathogenetic role of antiphospholipid antibodies in the development of thrombosis is still lacking, recent studies suggest that it is causative rather than coincidental. New insights on the possible mechanisms leading to thrombosis were provided by the discovery of the serum cofactor (β2-GPI), a coagulation inhibitor which is required for binding of anticardiolipin antibodies to cardiolipin. More recently, patients with antiphospholipid antibodies were found to possess autoantibodies directed against other coagulation factors, including prothrombin, protein C and protein S. Future studies should clarify whether these different antigenic specificities are associated with particular clinical events and assess the risk of thrombosis associated with the presence of antiphospholipid antibodies in asymptomatic individuals.

Antiphospholipid antibody syndrome in childhood strokes

The significance of antiphospholipid antibodies was examined in patients with childhood strokes. Eight patients, aged 2–13 years, who presented with acute hemiplegia were studied. On the basis of magnetic resonance imaging, magnetic resonance angiography, single photon emission computed tomography, and cerebral angiographic findings, 3 children were diagnosed as having infarctions due to moyamoya disease, and the others as having idiopathic infarctions. Serologic studies revealed elevated anticardiolipin antibody (ACA) IgG in 3 of the 5 patients with idiopathic infarction; no such elevation was revealed in patients with moyamoya disease. Values for all other tests, including ACA IgM and lupus anticoagulant, were within normal limits or negative in all patients. ACA IgG, therefore, may be a more important causative agent of childhood strokes than was previously considered.