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.

[Clinical and morphological correlations in patients with lupus nephritis: a retrospective study].

AIM: To analyze associations between clinical and morphological features of kidney involvement in patients with systemic lupus erythematosus. MATERIALS AND METHODS: In the retrospective cohort study, we enrolled adult (≥18 years) patients with morphologically proven lupus nephritis (LN) stratified according to the ISN/RPS classification. Systemic lupus erythematosus was classified in accordance with ACR/EULAR classification criteria (2019). Antiphospholipid syndrome was diagnosed according to the 2006 classification criteria. Disease activity was assessed with SELENA-SLEDAI score. RESULTS: We enrolled 62 patients with LN, among them 84% were females. Median age of SLE onset was 23 (16,3; 30,8) years. In all cases kidney involvement was accompanied by extrarenal manifestations, among which joint (82%), skin (57%) and hematological involvement (68%) was the most common. LN class I was proven in one patient, class II - in three patients, class III - in 24, including III+V in seven, class IV - in 18, including IV+V in two, class V - in 13, class VI - in three patients. APS nephropathy was diagnosed in 4 (6.5%) of patients with LN. The most common clinical manifestation was proteinuria (85%), however its prevalence, level and the frequency of nephrotic syndrome showed no significant differences between the LN classes. LN III/IV±V was characterized by the highest levels of serum creatinine (and the lowest eGFR) at the time of biopsy. CONCLUSION: LN is characterized by the high heterogeneity of the clinical and morphological manifestations, which makes LN class prediction impossible without kidney biopsy.

Perioperative management of a patient with systemic lupus erythematosus-associated antiphospholipid syndrome undergoing mandibular third molar surgery.

Antiphospholipid syndrome (APS) is a systemic autoimmune condition characterised by recurrent venous or arterial thrombosis and pregnancy complications, with persistent antiphospholipid autoantibodies. APS is often found in conjunction with other autoimmune diseases, such as systemic lupus erythematosus (SLE). SLE-associated APS patients may require dental procedures like tooth extractions. Due to the complex nature of this autoimmune disorder, perioperative management requires a comprehensive approach involving various medical specialists.These patients are frequently taking medications like anticoagulants, antiplatelet drugs, disease-modifying drugs and immunosuppressants. This medication regimen can increase their risk of postoperative complications, including bleeding, thrombosis, delayed healing and postoperative infections. Currently, there are no established guidelines for performing tooth extractions in individuals with SLE-associated APS.We report a case of SLE-associated APS with pericoronitis requiring surgical extraction. The purpose of this report is to offer practical recommendations for the perioperative management of dental procedures and alteration in medications used in such cases.

Transcatheter mitral valve-in-valve for pregnancy with anti-phospholipid syndrome: a case report.

BACKGROUND: Perioperative management and cardiac surgery in pregnant women with anti-phospholipid syndrome combined with heart valve disease have been rarely reported. CASE PRESENTATION: We describe a case of transcatheter mitral valve-in-valve replacement in a pregnant woman with bioprosthetic valve failure and anti-phospholipid syndrome at 18 weeks' gestation. The patient underwent a cesarean section delivery at 34 weeks of gestation, resulting in the birth of a healthy baby. CONCLUSIONS: Transapical mitral valve-in-valve surgery resulted in safe maternal and infant outcomes in a pregnant woman with anti-phospholipid syndrome combined with mitral bioprosthetic valve failure. The success of this procedure underscored the importance of multidisciplinary teamwork.

Antiphospholipid Syndrome Increases Postoperative Complications After Total Hip and Knee Arthroplasty.

BACKGROUND: Antiphospholipid syndrome (APS) is a systemic autoimmune condition that predisposes patients to venous thromboembolism (VTE). Although many studies have explored risk factors for VTE after joint reconstructive procedures, the impact of APS is still unclear. MATERIALS AND METHODS: A retrospective cohort study was conducted using TriNetX, a health care database that includes 442,494 patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA). Ninety-day postoperative complications and 1- and 2-year surgical complications were compared between patients with and without preexisting APS. Patients underwent propensity score matching in a 1:1 ratio based on relevant comorbidities. RESULTS: Patients undergoing THA or TKA with APS, compared with those without, had higher rates of deep venous thrombosis (hip: 9.2% vs 6.0%, odds ratio, 1.589, P=.022; knee: 10.5% vs 4.1%, odds ratio, 2.763, P<.001), pulmonary embolism (hip: 6.9% vs 3.6%, odds ratio, 1.992, P=.005; knee: 8.4% vs 3.0%, odds ratio, 2.989, P<.001), and anemia (hip: 24.8% vs 18.6%, odds ratio, 1.447, P=.004; knee: 18.5% vs 13.9%, odds ratio, 1.406, P=.007). Patients undergoing THA with APS also had higher rates of urinary tract infection (5.0% vs 2.8%, odds ratio, 1.842, P=.029) and pneumonia (3.7% vs 1.8%, odds ratio, 2.119, P=.025). APS did not impact rates of surgical complications or revision surgery. CONCLUSION: Overall, APS heightens patients' risk for complications after THA and TKA. Specific anticoagulation protocols and preoperative risk stratification should be implemented to reduce the risk of adverse events. [Orthopedics. 2024;47(5):301-307.].

Management of Anticoagulation and Antifibrinolytics in Catastrophic Antiphospholipid Syndrome.

Antiphospholipid syndrome (APS) is an autoimmune disorder that presents with hypercoagulability and results in a lab artifact of prolonged PTT. The most severe form is catastrophic antiphospholipid antibody syndrome (CAPS), which manifests as rapidly progressing thromboses in multiple organ systems leading to multi-organ ischemia. The mainstay management CAPS is anticoagulation and systemic corticosteroids. Antifibrinolytic agents have previously been thought to be relatively contraindicated in CAPS due to the pro-thrombotic nature of the disease; the complex coagulation profile of CAPS can make it difficult to assess the risks and benefits of antifibrinolytic therapy. Also, should a patient with CAPS require cardiopulmonary bypass (CPB) for surgery, it poses a unique challenge in providing appropriate anticoagulation in the setting of prolonged ACT. We present a case of a 32-year-old postpartum female with CAPS requiring heart transplant who safely received intraoperative antifibrinolytic therapy and was successfully anticoagulated during CPB after perioperative plasmapheresis.

Post-renal acute kidney injury complicated by urinary tract obstruction due to massive blood clots and severe thrombocytopenia in a patient with systemic lupus erythematosus: A case report.

Systemic lupus erythematosus (SLE) is often seen with antiphospholipid antibody syndrome (APS), and these conditions may occur concurrently with severe immune thrombocytopenia (ITP) and even acute kidney injury (AKI); however, post-renal AKI due to bleeding is uncommon. Here, we describe a case of post-renal AKI and anuria in a patient with SLE and APS, which were attributable to urinary tract obstruction due to massive blood clots caused by secondary ITP. A 50-year-old Japanese woman was admitted to our hospital with anuria, abdominal tenderness, purpura in the trunk and in both legs, and severe thrombocytopenia. She had been receiving medical treatment for APS and SLE till the age of 45 years. Computed tomography revealed a blood clot without extravasation in both urinary tracts, and she was diagnosed with post-renal AKI due to complete obstruction of the urinary system. Additionally, based on her medical history, elevated platelet-associated Immunoglobulin G (IgG) levels, and increased megakaryocyte count, she was diagnosed with secondary ITP complicated by SLE and APS. She also had elevated APS-related autoantibodies, including antiphosphatidylserine/prothrombin Immunoglobulin M (IgM), and IgG. However, concomitant serositis such as lupus enteritis or cystitis was not seen. She was treated with a combination of glucocorticoids, intravenous immunoglobulin, and continuous haemodialysis/haemofiltration, which resulted in rapid improvement of her symptoms and renal dysfunction. Secondary ITP-induced massive bleeding of urinary tract can cause post-renal AKI. Appropriate diagnosis and aggressive treatment are necessary to improve prognosis in such patients.

Cardiac involvement in the catastrophic antiphospholipid syndrome (CAPS): Lessons from the "CAPS registry".

OBJECTIVE: To analyze the demographic, clinical, and laboratory characteristics of catastrophic antiphospholipid syndrome (CAPS) patients with cardiac involvement, and to identify the factors associated with this cardiac involvement. MATERIAL AND METHODS: Based on the analysis of the "CAPS Registry", the demographic, clinical, and serological characteristics of patients with cardiac involvement were analyzed. Cardiac involvement was defined as heart failure, valvular disease, acute myocardial infarction, pericardial effusion, pulmonary arterial hypertension, systolic dysfunction, intracardiac thrombosis, and microvascular disease. Univariate and multivariate analysis was used for multiple comparisons. RESULTS: 749 patients (293 [39 %] women and mean age 38.1 ± 16.2 years) accounting for 778 CAPS events were included, of them 404 (52 %) had cardiac involvement. The main cardiac manifestations were heart failure in 185/377 (55 %), valve disease in 116/377 (31 %), and acute myocardial infarction in 104/378 (28 %). Of 58 patients with autopsy/biopsy, 48 (83 %) had cardiac thrombotic microangiopathy, Stroke (29% vs. 21 %, p = 0.012), transient cerebral vascular accident (2% vs. 1 %, p = 0.005), pulmonary infarction (26% vs. 3 %, p = 0.017), renal infarction (46% vs. 35 %, p = 0.006), acute kidney injury (70% vs. 53 %, p < 0.001), and livedo reticularis (24% vs. 17 %, p = 0.016) were significantly more frequent during CAPS events with versus without heart involvement. Multivariate analysis identified acute kidney injury (OR 1.068, IC 95 % 1.8-4.8, p < 0.001) as the only clinical characteristics that were, independently, associated with cardiac involvement in CAPS events. Cardiac involvement was not related to higher mortality. CONCLUSIONS: Cardiac involvement is frequent in CAPS, with association with kidney involvement, and it is not related to higher mortality. The presence of cardiac microthrombosis was demonstrated in most biopsies/autopsies performed.

[Coagulation Management During Open Heart Surgery Based on a Heparin Dose Sensitivity Test for Antiphospholipid Antibody Syndrome].

A 63-year-old woman with severe aortic regurgitation was admitted to our hospital due to congestive heart failure. She also had antiphospholipid syndrome (APS), necessitating strict coagulation management. Given her history of cerebellar infarction, deep vein thrombosis, and recurrent miscarriages, her thrombosis risk was higher, with all three types of antiphospholipid antibodies testing positive. Before the surgery, we created a heparin-activated clotting time (ACT) titration curve using the patient's blood, and the calculated ACT corresponding to the target heparin concentration of 3 U/ml was 650 seconds. We planned to administer heparin according to this target during cardiopulmonary bypass. The patient underwent an aortic valve replacement (AVR) using a bioprosthesis and was discharged without complications.

Anesthetic Management of a Jehovah's Witness Patient for Coronary Artery Bypass Grafting With Antiphospholipid Antibody Syndrome and Renal Transplant.

Anesthesia for cardiac surgical patients with antiphospholipid antibody syndrome (APLS) presents challenges with monitoring anticoagulation during cardiopulmonary bypass. Additionally, this condition is associated with other autoimmune diseases and comorbidities that need to be considered in caring for these patients, and there is minimal evidence for specific strategies during cardiac surgery. Separately, Jehovah's Witness (JW) patients typically do not consent to receiving blood products, presenting an additional challenge for resuscitation during cardiac surgery and especially in the context of APLS. We present our approach to the anesthetic management of a JW patient with systemic lupus erythematosus (SLE) complicated by APLS, thrombocytopenia, and renal failure with history of renal transplant who presented for coronary artery bypass surgery. Management strategies we recommend include administration of antifibrinolytics after heparinization to mitigate bleeding risk and interdisciplinary management with the perfusion, intensive care, surgical, and nephrology teams.

Risk Factors for Antiphospholipid Antibodies and Antiphospholipid Syndrome.

Persistence of serum antiphospholipid antibodies (aPL) is associated with a high thrombotic risk, both arterial and venous, and with pregnancy complications. Due to the potential morbidity and mortality associated with the presence of aPL, identifying and recognizing risk factors for the development of aPL and thrombosis in aPL carriers may help to prevent and reduce the burden of disease. Multiple elements are involved in the pathomechanism of aPL development and aPL-related thrombosis such as genetics, malignancy, and infections. This review will address the role of both well-known risk factors and their evolution, and of emerging risk factors, including COVID-19, in the development of aPL and thrombosis in aPL carriers.

Chronic abdominal aortic occlusive disease related to antiphospholipid syndrome: a rare presentation.

OBJECTIVE: Chronic abdominal aortic occlusive disease (CAAOD) is an uncommon manifestation of antiphospholipid syndrome (APS), impacting cardiovascular health and peripheral arterial circulation. We investigated CAAOD in antiphospholipid antibodies (aPL)-positive patients, aimed to offer comprehensive clinical and radiological insights. METHODS: aPL-positive patients with arterial thrombotic events were categorised into CAAOD and non-CAAOD. Extensive data, including clinical features, radiological images and outcomes, were analysed. RESULTS: This case-control study involved 114 patients who experienced arterial events from 2013 to 2021, revealing 12 patients with abdominal aortic stenosis or occlusion. The CAAOD group, predominantly young (36.67±11.83) males (75.00%), exhibited significantly higher rates of critical smoking habits (66.67% vs 25.49%, p=0.006) and hyperhomocysteinaemia (66.67% vs 31.37%, p=0.026). Radiological findings showed long-segment infrarenal aorta stenosis in CAAOD, occasionally involving renal and common iliac arteries. The lesions presented varying degrees of stenosis, including smooth lumen narrow and total vascular occlusion. Treatment modalities typically involved interventions or surgery, complementing anticoagulation therapy. CONCLUSION: The study shed light on the rare occurrence of CAAOD in APS, highlighting the roles of smoking and hyperhomocysteinaemia as notable risk factors. These findings emphasised the significance of early diagnosis and management of CAAOD.

Evaluation of Recurrent Pregnancy Loss.

Recurrent pregnancy loss (RPL) affects approximately 5% of couples. Although RPL definitions vary across professional societies, an evaluation after a second clinically recognized first-trimester pregnancy loss is recommended. Good quality evidence links parental chromosomal rearrangements, uterine anomalies, and antiphospholipid syndrome (APS) to RPL. In contrast, the relationship between RPL and other endocrine, hematologic, and immunologic disorders or environmental exposures is less clear. Anticoagulant therapy and low-dose aspirin are recommended for patients with RPL who have also been diagnosed with APS. Vaginal progesterone supplementation may be considered in patients experiencing vaginal bleeding during the first trimester. Surgical correction may be considered for patients with RPL in whom a uterine anomaly is identified. Evaluation and management of additional comorbidities should be guided by the patient's history rather than solely based on the diagnosis of RPL, with the goal of improving overall health to reduce complications in the event of pregnancy. Most people with RPL, including those without identifiable risk factors, are expected to achieve a live birth within 5 years from the initial evaluation. Nevertheless, clinicians should be sensitive to the psychological needs of individuals with this condition and provide compassionate and supportive care across all stages.

Clinical presentation and outcomes in patients with antiphospholipid syndrome-associated adrenal hemorrhage. A multicenter cohort study and systematic literature review.

BACKGROUND: Adrenal hemorrhage (AH) can occur in patients with antiphospholipid Syndrome (APS). We aimed to characterize the clinical manifestations, treatments, and outcomes of patients presenting with APS-associated AH (APS-AH) through a retrospective cohort and a systematic literature review (SLR). METHODS: We performed a mixed-source approach combining a multicenter cohort with an SLR of patients with incident APS-AH. We included patients from Mayo Clinic and published cases with persistent positivity for antiphospholipid antibodies and presenting with AH, demonstrated by imaging or biopsy. We extracted demographics, clinical characteristics, laboratory findings, treatment strategies, and outcomes (primary adrenal insufficiency and mortality). We used Kaplan-Meier and Cox models for survival analysis. RESULTS: We included 256 patients in total, 61 (24%) from Mayo Clinic and 195 (76%) from the SLR. The mean age was 46.8 (SD 15.2) years, and 45% were female. 69% of patients had bilateral adrenal involvement and 64% presented adrenal insufficiency. The most common symptoms at presentation were abdominal pain in 79%, and nausea and vomiting 46%. Hyponatremia (77%) was the most common electrolyte abnormality. Factors associated with primary adrenal insufficiency were bilateral adrenal involvement at initial imaging (OR 3.73, CI; 95%, 1.47-9.46) and anticardiolipin IgG positivity (OR 3.80, CI; 95%, 1.30-11.09). The survival rate at five years was 82%. History of stroke was associated with 3.6-fold increase in mortality (HR 3.62, 95% CI; 1.33-9.85). CONCLUSION: AH is a severe manifestation of APS with increased mortality. Most patients developed permanent primary adrenal insufficiency, particularly those positive for anticardiolipin IgG and bilateral adrenal involvement.

A case of repeated in-stent restenosis of coronary artery as a primary manifestation of seronegative antiphospholipid antibody syndrome.

BACKGROUND: Antiphospholipid antibody syndrome (APS) is a multisystemic autoimmune disorder which affects many organs or systems; however, coronary artery is relatively less frequently involved. CASE PRESENTATION: A 65-year-old female with effort chest pain was hospitalized for unstable angina in Janurary, 2015. Coronary angiography revealed sub-total occlusion of proximal left anterior descending (LAD) coronary artery, where a drug-eluting stent was successfully deployed. The patient experienced multiple in-stent stenosis at LAD coronary artery and coronary artery bypass graft (CABG) surgery was advised. Subsequently, severe stenosis of left circumflex (LCX) coronary artery emerged, and the patient suffered persistent in-stent restenosis. Eventually, the patient was diagnosed with seronegative antiphospholipid antibody syndrome and salvaged by immunosuppressants. CONCLUSIONS: Repeated in-stent restenosis could be a primary manifestation of seronegative antiphospholipid antibody syndrome, and suppression of autoimmune activity and inflammation other than purely coronary revascularization might be a better option.

A Case of Catastrophic Antiphospholipid Syndrome with Acute Multiorgan Thrombosis and Concerns for Re-Emergence.

BACKGROUND Catastrophic antiphospholipid syndrome (CAPS) is a rare, life-threatening form of antiphospholipid syndrome characterized by widespread thrombotic complications leading to multiorgan ischemia and failure. Although there are no standard treatment guidelines for CAPS, it often involves triple therapy with anticoagulation, corticosteroids, and plasma exchange. Recently, biologics such as rituximab and eculizumab have also shown promise as potential new therapies for CAPS, as observed in our case. CASE REPORT We describe a 59-year-old female patient who presented with altered mental status and diffuse weakness. Imaging studies revealed multiorgan thrombosis along with thrombocytopenia that markedly improved with plasma exchange therapy, steroids, and a heparin drip. While the exact etiology of CAPS remained unknown, it was likely precipitated by her warfarin discontinuation and confirmed Haemophilus influenzae infection. The patient's hospital course was complicated by hemorrhagic shock after a renal biopsy, followed by an acute drop in thrombocytopenia and new embolic infarcts in the brain that raised concern for CAPS re-emergence. To address the refractory nature of her condition, the patient underwent a trial of rituximab, which remarkably improved her clinical picture and platelet count by an 8-fold increase within 1 week. CONCLUSIONS This case highlights the importance of early recognition and diagnosis of catastrophic antiphospholipid syndrome, a true rheumatological emergency that requires aggressive treatment to prevent irreversible complications. Our patient's presentation and response to treatment also underscores the complexity of managing CAPS and the use of newer biological therapies in refractory cases.

Ischemic Stroke with Positive Antiphospholipid Antibodies in Bloom Syndrome: A Case Report.

OBJECTIVE: Bloom syndrome is a chromosomal breakage disorder associated with immune deficiency, characterized by short stature, predisposition to early-onset cancer, and immune defects. Currently, there have been no reports of acute cerebral infarction in patients with Bloom syndrome. Here, we report a case of Bloom syndrome complicated by elevated antiphospholipid antibodies and acute cerebral infarction. MATERIALS AND METHODS: A 23-year-old male with a known genetic diagnosis of Bloom syndrome was admitted to the Respiratory Department due to pulmonary aspergillosis. The patient experienced sudden dizziness, and subsequent cranial MRI revealed a newly developed infarction in the right cerebellar hemisphere. RESULTS: Six days later, the patient presented with sudden right visual field loss, and a repeat cranial MRI showed new infarctions in the left occipital and temporal lobes. Positive lupus anticoagulant and prolonged activated partial thromboplastin time suggested elevated antiphospholipid antibodies causing thrombus formation. Unfortunately, anticoagulant treatment was not administered due to recurrent hemoptysis. CONCLUSION: This study reports the first case of a Bloom syndrome patient with elevated antiphospholipid antibodies and acute cerebral infarction, suggesting that the immune and coagulation abnormalities caused by Bloom syndrome may contribute to the development of acute cerebral infarction.

Efforts to Better Characterize "Antiphospholipid Antibody Nephropathy" for the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria: Renal Pathology Subcommittee Report.

OBJECTIVE: Antiphospholipid antibody (aPL) nephropathy (-N) can be challenging to recognize due to a lack of established classification or diagnostic criteria. As part of efforts to develop new antiphospholipid syndrome (APS) classification criteria (CC), the APS CC Renal Pathology Subcommittee aimed to better characterize the entity of aPL-N. METHODS: We used a 4-pronged approach that included (1) administering Delphi surveys to worldwide APS physicians to generate aPL-N terminology; (2) conducting a literature review to demonstrate the association of nephropathy with aPL and identify published aPL-N histopathological terminology and descriptions; (3) evaluating aPL-N terminology used in renal biopsy reports from an international patient registry; and (4) evaluating proposed kidney pathologic features for aPL-N by assessment of international Renal Pathology Society (RPS) members. RESULTS: After completing our metaanalysis demonstrating an association between nephropathy and aPL, we used Delphi surveys, a literature review, and international renal biopsy reports to develop a preliminary definition of aPL-N. The preliminary definition included include specific terms associated with acute (ie, thrombotic microangiopathy in glomeruli or arterioles/arteries) and chronic (ie, organized arterial or arteriolar microthrombi with or without recanalization, organized glomerular thrombi, fibrous and fibrocellular [arterial or arteriolar] occlusions, focal cortical atrophy with or without thyroidization, and fibrous intimal hyperplasia) lesions. Most RPS survey respondents agreed with this terminology and the importance of knowing aPL results for histopathological diagnosis. CONCLUSION: Our results support the inclusion of aPL-N in the 2023 American College of Rheumatology/European Alliance of Associations for Rheumatology APS CC, and provide the most widely accepted terminology to date for both acute and chronic pathologic lesions of aPL-N.

The estimated prevalence of antiphospholipid antibodies and criteria-antiphospholipid syndrome in subjects with renal thrombotic microangiopathy.

BACKGROUND: While the prevalence of antiphospholipid antibodies (aPL) in venous and arterial thrombotic events had already been estimated by previous studies, the prevalence of aPL in subjects with Thrombotic Microangiopathy (TMA) is still not fully elucidated. Thus, we conducted a systematic review to estimate the frequency of aPL in subjects with biopsy-proven renal TMA. METHODS: We conducted in the PubMed database a search for English-language studies investigating the presence of aPL in subjects with biopsy-proven renal TMA from January 1985 to December 2022. Keywords used in the search included: 'antiphospholipid syndrome', 'antiphospholipid antibodies' and 'thrombotic microangiopathy'. Cohorts of HUS patients were excluded due to the risk of over-estimating the prevalence of aPL in these populations. The median frequency for positive aPL including anticardiolipin antibodies (aCL), antibodies against ß2-glycoprotein-I (anti-ß2GPI) and lupus anticoagulant (LA) was then calculated. RESULTS: 522 articles were identified through the literature search. Six studies, assessing the prevalence of aPL in 211 subjects with renal TMA, were retrieved. The overall aPL prevalence was estimated as 24.4% (range 22-56). The estimated prevalence of aCL (IgG/IgM), anti-ß2GPI, (IgG/IgM) and LA was 4.0% (range 3-27), 4.0% (range 3-16) and 18.9% (range 13-25), respectively. APS was diagnosed in 16.3% (range 11-29) of the patients. Of note, a high level of heterogeneity was observed when comparing the reported aPL profiles for each study. CONCLUSIONS: This comprehensive systematic analysis of studies investigating the prevalence of aPL in renal TMA showed that, despite the high heterogeneity of the included studies, aPL are present in about one case out of four renal-TMA cases.