Cell-bound complement activation products in antiphospholipid antibody-positive patients without other systemic autoimmune rheumatic diseases.

The objective of this study was to analyze complement activation in antiphospholipid antibody (aPL)-positive patients without other systemic autoimmune rheumatic diseases, using C3/C4 and cell-bound complement activation products (CB-CAPs) (B-lymphocytes [BC4d], erythrocytes [EC4d], and platelets [PC4d]). Persistently aPL-positive patients with or without aPL-related clinical manifestations (thrombotic APS [TAPS], microvascular APS [MAPS], obstetric APS, thrombocytopenia [TP], and/or hemolytic anemia [HA]) were enrolled in a single center study. Blood and clinical data were collected at baseline; a subgroup of patients completed 6- or 12-month follow-up. At baseline, 4/31 (13%) patients had decreased C3/C4, while 7/29 (24%) had elevated BC4d, 11/33 (33%) EC4d, and 12/32 (38%) PC4d. Based on different aPL profiles, all patients with decreased C3/C4 or elevated BC4d, EC4d, and PC4d had triple aPL or isolated lupus anticoagulant positivity. Based on different aPL clinical phenotypes, the number of patients with strongly positive EC4d and PC4d were proportionally higher in those with MAPS/TP/HA, compared to TAPS or no APS. Compared to baseline, the frequencies of BC4d, EC4d, and PC4d positivity were not significantly different in the subgroup of patients during their 6- or 12-month follow-up. There was a weak correlation between C3/C4 and CB-CAPs, especially for PC4d. In summary, complement activation in aPL-positive patients varies based on aPL profiles and clinical phenotypes. Given the higher percentage of aPL-positive patients with abnormal CB-CAPs, compared to C3/C4, and the poor inverse correlation between CB-CAPs and C3/C4, our study generates the hypothesis that CB-CAPs have a role in assessing disease activity and thrombosis risk in aPL-positive patients.

Dancing with disorder: chorea - an unusual and neglected manifestation of antiphospholipid syndrome.

OBJECTIVES: Chorea, characterised by involuntary, irregular movements, is a rare neurological manifestation of antiphospholipid syndrome (APS). The specific clinical features remain unclear. This study aimed to summarise the available evidence on antiphospholipid antibody (aPL)-associated chorea. METHODS: We used a mixed-methods approach, combining data from patients with chorea with aPL positivity admitted to Peking Union Medical College Hospital (PUMCH) from 2014 to 2024, with cases identified in public databases since 1983. We collected and analysed clinical, laboratory, and imaging results, along with their treatments and outcomes. RESULTS: A total of 180 patients with incident aPL-associated chorea were included (13 from PUMCH and 167 from the literature). The majority (81.7%) were female, with a mean age of chorea onset 22.8 years (SD=16.0). Chorea was the initial symptom in 87.9% of cases and often occurred as a single episode (67%), involving bilateral limbs (58.8%) and both upper and lower limbs (87.2%). 43.3% met the 2023 American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) APS classification criteria. Thrombocytopenia (30.0%) and arterial thrombosis (29.1%) were the most common manifestations. Lupus anticoagulant was positive in 84.2% of patients, anticardiolipin IgG in 70.8%, and anti-ß2 glycoprotein I IgG in 52.9%. Among those who had results available for the three tests, 57.6% were triple-positive. ANAs were positive in 63.6%. MRI revealed basal ganglia lesions in only 14.8% of patients, whereas all positron emission tomography (PET) scans showed contralateral striatal hypermetabolism. Treatment varied, with most receiving combination therapies of neuroleptics, anticoagulants, antiplatelets, steroids and immunosuppressants. Chorea completely or partially improved in 95.5% of patients. CONCLUSION: Chorea is a significant but under-recognised manifestation of APS, predominantly affecting young women and often presenting as the initial symptom. Characteristic PET findings of contralateral striatal hypermetabolism can assist in diagnosis. Treatments with glucocorticoids and immunosuppressive therapies appear beneficial. Further research is needed to understand the pathophysiology and optimise management strategies for aPL-associated chorea.

Antiphospholipid Antibodies Modify the Prognostic Value of Baseline Platelet Count for Clinical Outcomes After Ischemic Stroke.

BACKGROUND: Antiphospholipid antibodies (aPLs) have been reported to be involved in platelet-mediated thrombosis and inflammation, but the impact on the prognosis of ischemic stroke remains unclear. We aimed to examine whether the association between baseline platelet count (PLT) and long-term clinical outcomes within 2 years after ischemic stroke onset is modulated by aPLs. METHODS AND RESULTS: A total of 2938 patients with ischemic stroke were included in this prospective cohort study. Cox proportional hazards regression models were used to assess the association between the baseline PLT stratified by aPLs status and 2-year clinical outcomes after stroke onset, and an interaction effect between PLT and aPLs on clinical outcomes was tested by likelihood ratio test. There was a significant interaction effect of aPLs and PLT on recurrent stroke (Pinteraction=0.002) and cardiovascular events (Pinteraction=0.001) within 2 years after stroke onset. After multivariate adjustment, high PLT was associated with increased risks of recurrent stroke (hazard ratio [HR], 2.78 [95% CI, 1.03-7.45]; Ptrend=0.039) and cardiovascular events (HR, 2.58 [95% CI, 1.12-5.90]; Ptrend=0.024) when 2 extreme tertiles were compared among patients with aPL positive, but not among those with aPL negative. CONCLUSIONS: The aPLs had a modifying effect on the association between PLT and clinical outcomes within 2 years after ischemic stroke onset. Increased PLT was associated with recurrent stroke and cardiovascular events after ischemic stroke onset among patients with aPL positive, but not in those with aPL negative.

Clinical Features Between Primary Obstetric Antiphospholipid Syndrome and Non-Criteria Obstetric Antiphospholipid Syndrome and Risk Factors of Adverse Pregnancy Outcomes: A Retrospective Study of 1006 Cases.

PROBLEM: To compare the clinical characteristics and pregnancy outcomes between patients with primary obstetric antiphospholipid syndrome (OAPS) and those with primary non-criteria obstetric antiphospholipid syndrome (NC-OAPS), and to identify the risk factors of adverse pregnancy outcomes in both groups. METHODS: A retrospective single-center study was performed in a university hospital of western China, including 141 patients with OAPS and 865 patients with NC-OAPS. The clinical characteristics, pregnancy complications, and obstetric outcomes of the cohorts were collected from the hospital system and were compared by univariable analysis, and the independent risk factors for adverse pregnancy outcomes (APO) were investigated by logistic regression analysis in these two populations. RESULTS: The OAPS patients had a significantly higher risk for stillbirths compared to the NC-OAPS patients, while the NC-OAPS group had a significantly higher risk for preterm birth and overall APO. Double aPL positivity, triple aPL positivity, and gestational hypertension were the independent risk factors for APO in OAPS patients, whereas two of the double aPL positivity subtypes, triple aPL positivity and placenta previa were independent risk factors for APO in NC-OAPS patients. CONCLUSION: This study identified different rates in different APOs among OAPS and NC-OAPS patients. Additionally, this study revealed different risk factors for the development of APO between the two populations. These findings indicated that OAPS and NC-OAPS are two distinct entities of the same disease, providing new insights into the individualized management for patients with OAPS and NC-OAPS.

Risk factors for cerebral infarction and cerebrovascular stenosis in antiphospholipid antibody-positive patients: A retrospective single-center study with propensity score matching analysis.

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the presence of antiphospholipid antibodies (aPLA), such as anticardiolipin (aCL), anti-ß2-glycoprotein I (aß2GPI), or lupus anticoagulant (LA). Although cerebrovascular events are commonly associated with APS, comprehensive studies on risk factors for cerebral infarction in aPLA-positive patients remain sparse. In this retrospective single-center study, data from 9844 patients tested for aPLA between January 2017 and March 2023 were analyzed. A total of 647 aPLA-positive patients were included, with assessments of various factors including age, gender, hypertension, diabetes, dyslipidemia, smoking history, and cardiac disease. Propensity score matching was employed to create 2 matched groups of 202 patients each, comparing those with and without cerebral infarction. Logistic regression analyses were conducted to identify risk factors for cerebral infarction and progression of cerebrovascular stenosis. The mean age of the study cohort was 65.8 years, with 60% being male. LA was positive in 95.2% of the cases, aCL in 8.8%, and aß2GPI in 5.3%. High-risk aPLA profiles were identified in 7.1% of the cases. In the cerebral infarction group, both smoking history and aCL positivity were significantly associated with an increased risk (OR = 1.543; 95% CI: 1.020-2.334; P = .040 and OR = 3.043; 95% CI: 1.426-6.491; P = .040, respectively). Male gender and posterior circulation involvement were significant risk factors for exacerbation of cerebrovascular stenosis (OR = 3.73; 95% CI: 1.16-16.69; P = .046 and OR = 5.41; 95% CI: 1.80-16.05; P = .002, respectively). Smoking history and aCL positivity are prominent risk factors for cerebral infarction in aPLA-positive patients, while male gender and involvement of the posterior circulation emerge as significant risk factors for the progression of cerebrovascular stenosis. Further comprehensive prospective studies are necessary to deepen understanding of aPLA-related cerebrovascular diseases.

Establishment of cutoff values for anti-ß2 glycoprotein I antibodies in women of reproductive age in Southwest China.

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by vascular thrombosis and obstetric morbidity, with accurate laboratory examination of antiphospholipid antibodies (aPLs) being crucial for diagnosis. This study focused on anti-ß2 glycoprotein I (aß2GPI) antibodies and aimed to establish the first population-based cutoff values for aß2GPI IgA/IgM/IgG antibodies in non-pregnant women of reproductive age in Southwest China. The study cohort comprised 181 healthy women of reproductive age for study. Blood samples were collected on an early morning fast. Anti-ß2GPI antibodies including IgA, IgM and IgG were measured in serum using the HOB® BioCLIA kit. According to the Clinical and Laboratory Standards Institute (CLSI) guidelines, the study used non-parametric percentile methods to calculate the 95th, 97.5th, and 99th percentiles cutoff values for aß2GPI IgA/IgM/IgG antibodies, along with corresponding 90% confidence intervals (CI), while excluding outliers. A total of 168 independent samples were collected for verification, including 85 samples from healthy subjects and 83 samples from APS patients, in order to evaluate the analytical performance of the obtained cutoff values. The 99th percentile cutoff values were 3.36 RU/mL for aß2GPI IgA, 27.54 RU/mL for aß2GPI IgM and 1.81 RU/mL for aß2GPI IgG, which indicated that the levels of aß2GPI IgM antibodies were generally higher compared to those of IgA and IgG antibodies. Our established reference range was confirmed to be successful in validating the detected values of aß2GPI antibodies in all healthy controls. With the 99th percentile cutoff value, the sensitivity was 14.46% for aß2GPI IgA, 22.89% for aß2GPI IgG, and 9.64% for aß2GPI IgM in APS patients. This study established population-based cutoff values that are applicable to the local population for the accurate laboratory examination of aß2GPI antibodies in non-pregnant women of reproductive age. The study also recommends paying more attention to IgM positivity in women of reproductive age.

Converging pathways: acquired von Willebrand disease in systemic lupus erythematosus with antiphospholipid antibodies presenting with persistent menstrual bleeding.

We present a case of a woman in her 20s with inadequately treated systemic lupus erythematosus (SLE). She presented with heavy menstrual bleeding, along with nasal and gum bleeding worsening over 3 months. There was no bleeding history in her family, childhood, dental procedures or childbirth. Evaluation ruled out structural causes, revealing prolonged activated partial thromboplastin time (incomplete correction on mixing studies), normal prothrombin time, moderate thrombocytopenia, and lupus anticoagulant and anti-phosphatidylserine/prothrombin antibody positivity twice, 12 weeks apart. Further evaluation showed very low von Willebrand factor (vWF) levels (<5%). She was treated with pulse methylprednisolone for 3 days, resulting in complete symptom resolution and improvement in vWF levels to 130%. The absence of bleeding history, family history, presence of very low vWF and its response to corticosteroids led to a diagnosis of acquired vWF syndrome as the cause of mucosal bleeding in an SLE patient with concomitant positive antiphospholipid antibody. She was discharged on hydroxychloroquine, mycophenolate mofetil and tapering oral corticosteroids.

Vitamin K Antagonists for Pregnant Women With Antiphospholipid Antibodies: A Scoping Review.

OBJECTIVE: To describe characteristics of published research on the safety and efficacy of vitamin K antagonists (VKA) for pregnant patients with antiphospholipid antibodies (aPL), including their methodological characteristics and knowledge gaps. METHODS: This study followed the Joanna Briggs Institute methodology for scoping reviews and used the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews protocol system. Studies were primarily identified through searching electronic databases including MEDLINE, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials. Study characteristics and outcomes were reported and described using customized charting tables. RESULTS: Of 1528 publications, 17 remained in the final analysis. These reported up to 190 VKA-treated aPL-positive pregnancies diagnosed as antiphospholipid syndrome (APS); pregnancy cases were likely overlapping in some publications. In the 17 reports, there were 723 individuals in comparison groups, including healthy pretreatment pregnancies and women with APS treated with standard therapies without VKA. However, only 4 (23.5%) of the 17 publications stated a study objective focusing on VKA use, of which only one was a full-length article. In addition, information on VKA doses, disease diagnostic criteria, and the long-term outcomes of offspring were largely absent. CONCLUSION: The current evidence is insufficient to assess VKA efficacy and safety profiles in aPL-positive pregnant patients. Studies with a defined focus on VKA use in this population are lacking, and reporting of key information is not consistent. The relative lack of knowledge of VKA use in pregnant women with APS is concerning, and efficacy and safety questions remain.

TO SHOw how we have been ENgaged in the APS FiELD (What we learned on APS collaborating with Professor Yehuda Shoenfeld).

The present review reports the history of our scientific collaboration with Professor Shoenfeld's group. The collaboration started at the end of the 80s and was mainly focused on studies on the pathogenetic mechanisms of the anti-phospholipid syndrome (APS). Following the initial collaborative studies on antibodies against endothelium in systemic autoimmune vasculitis, we were able to use a similar strategy in APS. This line of research has resulted in the characterization of beta 2 glycoprotein I (ß2GPI)-dependent anti-phospholipid antibodies (aPL) as mechanisms capable of mediating an endothelial perturbation crucial for the pathogenesis of APS. Thanks to these studies, the collaboration has led to the characterization of the membrane receptors for ß2GPI and the cellular signaling resulting from antibody binding. This mechanism has also been shown to mediate the aPL effect on other cell types involved in APS pathogenesis. Finally, the exchange of information made it possible to replicate and extend the setting of animal models of the syndrome, which proved to be valuable tools for understanding the pathogenesis of the syndrome. It has been a long story recently refueled by common studies on the similarity of pro-inflammatory and pro-coagulant endotheliopathy in APS and in COVID-19.

Comparison of clinical and serological features in thrombotic antiphospholipid syndrome patients, with and without associated systemic lupus erythematosus, followed for up to 42 years: A single centre retrospective study.

OBJECTIVE: To assess the impact of concomitant systemic lupus erythematosus (SLE) on the clinicopathological manifestations of thrombotic antiphospholipid syndrome (APS). METHODS: This single-centre, retrospective study compared clinical and antiphospholipid antibody (aPL) data from 118 patients, 58 with SLE-associated APS (SLE-APS), and 60 with primary APS. RESULTS: Median follow-up was 13.9 (IQR 7.7-19.3) and 8.6 years (3.5-10.6) for the SLE-APS cohort and PAPS cohort, respectively. Age at diagnosis of APS was lower in the SLE-APS cohort (mean 35.9 vs PAPS: 46.7 years; p < 0.05). Distribution of aPL subtypes was similar across cohorts. 198 thrombotic events were identified overall (index plus recurrent), with venous thromboembolism (VTE) and arterial thrombosis each occurring in just over half of patients in both cohorts. Microvascular thrombosis (12.1% vs 0%), and a mixed (any combination of venous, arterial and microvascular) thrombotic phenotype (19.0% vs 6.7%, p = 0.05) were more prevalent in SLE-APS patients. Recurrent thrombosis incidence rates (∼0.5 events/10-patient years), and Kaplan-Meier recurrence-free survival after index thrombosis, were similar. In the PAPS cohort, only: (i) triple-aPL-positivity was associated with a significantly higher recurrent thrombosis event rate (incidence rate ratio 2.22, p = 0.03) and lower recurrence-free survival after first thrombosis (log-rank test p = 0.01); (ii) lupus anticoagulant (LA)-positivity was associated with higher prevalance of arterial thrombosis (RR 2.69, p = 0.01), and lower prevlance of VTE (RR 0.48, p < 0.001), versus LA-negativity. CONCLUSION: Concomitant SLE does not appear to modify long-term recurrent thrombosis risk, or aPL phenotypes, in patients with APS. Triple-aPL-positivity and LA-positive status may have less influence on thrombotic outcomes in patients with SLE-APS compared to PAPS.

Thrombotic antiphospholipid syndrome: From guidelines to clinical management.

Thrombotic manifestations, mainly venous thromboembolism (VTE) and stroke, are the most common and potentially life-threatening presentations of antiphospholipid syndrome (APS). The management of APS requires the assessment of the antiphospholipid antibodies (aPL) profile, of concurrent systemic lupus erythematosus or other systemic autoimmune diseases and the presence of risk factors for cardiovascular disease and bleeding. Anticoagulation with vitamin K antagonists (VKA) remains the cornerstone of therapy for thrombotic APS. As platelets play a central role in APS, low-dose aspirin is the first option for primary thromboprophylaxis in asymptomatic aPL carriers, and also plays a role as combination therapy with VKAs in arterial thrombosis. Treatment with direct oral anticoagulants (DOACs) could be considered in certain low-risk situations, although they are not recommended in patients with arterial thrombosis or triple positive aPL. Adjuvant therapies such as hydroxychloroquine and statins may be useful in complex settings such as thrombotic recurrences or high risk of bleeding. In this article, we review the evidence and the recommendations of the guidelines for the treatment of APS, and provide a critical and practical approach of its management from our clinical perspective.

Antiphospholipid antibody testing.

Antiphospholipid antibodies (aPL) are a family of autoantibodies targeting phospholipid-binding proteins and are associated with several clinical settings, and most notably define the antiphospholipid syndrome (APS). These antibodies can be identified using a variety of laboratory tests, which include both solid-phase immunological assays and functional clotting assays that detect lupus anticoagulants (LA). aPLs are linked to a range of adverse medical conditions, such as thrombosis and complications affecting the placenta and fetus, potentially leading to morbidity and mortality. The specific aPL identified, along with the pattern of reactivity, correlates with the severity of these conditions. Therefore, laboratory testing for aPL is crucial for evaluating the risk of complications and for fulfilling certain classification criteria for APS, which are also applied as diagnostic markers in medical practice. This review provides an overview of the available laboratory tests currently for measuring aPL and discusses their clinical implications.

Progress in the field of animal models of antiphospholipid syndrome.

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by recurrent arteriovenous thrombosis and pathological pregnancy, accompanied by persistent antiphospholipid antibodies, (aPL). The incidence of APS is increasing year by year, clinicians lack of understanding of this type of disease, easy to misdiagnose and miss the diagnosis. Therefore, it is extremely important to establish a suitable animal model to reduce the process of disease development as much as possible and improve clinicians' understanding and understanding. This review will summarize the animal models of APS from the aspects of modeling methods, modeling mechanism, evaluation indicators and advantages and disadvantages of methods, providing a reference for finding an animal model highly similar to human APS, helping researchers to further clarify the pathogenesis of APS and find potential therapeutic targets, so as to achieve early diagnosis, early intervention, and ultimately improve the prognosis of patients.

Biological markers of high risk of thrombotic recurrence in patients with antiphospholipid syndrome: A literature review.

OBJECTIVES: This review aims to identify biological markers associated with the risk of recurrence of thrombotic and/or obstetric events in patients with antiphospholipid syndrome (APS). METHODS: A comprehensive review of literature was conducted to evaluate established and potential novel biological markers associated with thrombosis in APS. To this end, a PubMed literature search was conducted for the last twenty years using the following keywords or their combinations: thrombotic risk, recurrence of thrombosis, risk stratification, severity, predictive value. RESULTS: Previous studies showed that multiple aPL positivity correlates with an increased risk of thrombosis in APS. Moreover, the analysis of N-glycosylation of antiphospholipid antibodies (aPL) revealed that low levels of IgG sialylation, fucosylation or galactosylation increases the pro-inflammatory activity of aPL, predisposing to thrombosis. In addition, quantification of neutrophil extracellular traps (NETs) and antibodies directed against NETs (anti-NETs) in serum demonstrates promising prognostic utility in assessing APS severity. Oxidative stress plays a role in the pathogenicity of APS and paraoxonase 1 (PON1) activity emerges as a promising biomarker of thrombotic risk in APS. Furthermore, identification of novel antigenic targets involved in the pathophysiology of APS, such as lysobisphosphatidic acid (LBPA), had led to the discovery of unconventional aPL, antibodies directed against the LBPA (aLBPA), whose clinical value could make it possible to identify APS patients at high risk of thrombotic recurrence. CONCLUSION: The immunological profile of aPL, N-glycosylation of aPL, quantification of NETs and anti-NETs, analysis of biomarkers of oxidative stress and the discovery of aLBPA offer potential prognostic tools for risk stratification in APS patients.

Non-criteria and criteria antiphospholipid antibodies and their association with pregnancy outcomes in women with a history of miscarriage: A retrospective study.

INTRODUCTION: The objective of this study was to investigate both antiphospholipid antibodies (aPLs) and non-criteria aPLs (NC-aPLs) in relation with pregnancy outcomes. METHODS: We retrospectively analyzed 1574 pregnant women with experienced at least one miscarriage who were tested for aPLs and NC-aPLs, and compared their clinical characteristics, immune biomarkers, and pregnancy outcomes. The χ2 test or Fisher's exact test compared pregnancy outcomes among patients negative for all aPLs, positive for NC­aPLs subtypes, and positive for criteria aPLs subtypes. RESULTS: Multivariate logistic regression analysis indicated that positive aPLs (OR = 2.216, 95 % CI 1.381-3.558), and positive NC-aPLs (OR = 1.619, 95 % CI 1.245-2.106) are linked to adverse outcomes. For fetal loss, positive aPLs (OR = 2.354, 95 % CI 1.448-3.829), NC-aPLs (OR = 1.443, 95 % CI 1.076-1.936) were significant. Premature delivery was associated with positive NC-aPLs (OR = 2.102, 95 % CI 1.452-3.043). In the NC-aPLs positive group, the rate of adverse outcomes was higher in the multiple-positive subgroup (77.8 %) compared to the double-positive (52.3 %) and single-positive (37.0 %) subgroups. The rates of fetal loss and premature delivery were also higher in the multiple-positive NC-aPLs subgroup compared to the single-positive subgroup (48.1 % vs. 22.6 % for fetal loss and 57.1 % vs. 16.5 % for premature delivery). DISCUSSION: Our findings suggest that both aPLs and NC-aPLs are associated with an increased incidence of adverse pregnancy outcomes, and patients presenting with multiple NC-aPLs positivity were found to have a higher incidence of adverse outcomes compared to their single-positive counterparts.

Effect of vitamin D3 on antiphospholipid antibodies in hospitalized patients with moderate to severe COVID-19.

OBJECTIVE: To investigate the effect of a single oral dose of 200,000 IU of vitamin D3 on antiphospholipid antibodies in hospitalized patients with moderate to severe COVID-19. METHODS: This is a post-hoc, exploratory analysis from a double-blind, placebo-controlled, randomized clinical trial performed in two centers in Sao Paulo, Brazil. Hospitalized patients with COVID-19 were randomly assigned to receive either vitamin D3 (n = 97) or placebo (n = 97). In this post-hoc analysis, the endpoints were titers and frequency of anti-ß2-Glycoprotein-I (aß2-GP) and Anticardiolipin (aCL) antibodies [Immunoglobulin G, M and A (IgG, IgM and IgA)]. RESULTS: Overall mean (SD) age was 55.3 (13.9) years, Body Mass Index (BMI) was 32.2 (7.1 kg/m2), and 106 participants (54.6 %) were male. There was a significant group by time interaction (p = 0.046) for frequency of aCL IgG, with increased values from baseline to discharge in the placebo group [n (%), from 13 (13.4) to 25 (25.8)] compared to the vitamin D3 [from 25 (25.8) to 29 (29.9)]. However, the frequency of aCL IgG did not change between the groups on discharge. No significant differences between vitamin D3 and placebo groups were found for any other autoantibodies. CONCLUSION: These findings do not support the use of a single oral dose of 200,000 IU of vitamin D3 to modulate autoantibodies in hospitalized patients with moderate to severe COVID-19.

Antiphospholipid syndrome in children.

Antiphospholipid syndrome (APS) in children is a rare disease associated with significant morbidity and mortality. In comparison with APS in adults, pediatric APS has a more severe presentation with frequent recurrences of thrombotic events and a higher probability of life-threatening catastrophic APS. Nonthrombotic manifestations are also more common in the pediatric age group and can precede thrombosis. New classification criteria have been introduced recently and have not yet been assessed in pediatric patients with APS. In addition to anticoagulation drugs, other novel therapies have emerged including the use of B cell and complement inhibitors, especially in catastrophic APS. The purpose of this review is to provide a broad overview of aPL-related clinical manifestations in pediatric patients based on the analysis of published cohorts and data from the international pediatric APS registry. We also aim to illustrate APS in infants caused by transplacentally transferred maternal aPL, which is very rarely associated with acute thrombotic events in the perinatal period and more frequently with long-term neurodevelopmental abnormalities.