The clinical significance of low complement levels in patients with catastrophic antiphospholipid syndrome: A descriptive analysis of 73 patients from the "Catastrophic antiphospholipid syndrome registry"

Emergencies in inflammatory rheumatic diseases

Inflammatory rheumatic diseases (IRDs), encompassing a broad spectrum of chronic disorders, typically necessitate prolonged therapeutic intervention. Nevertheless, these diseases can sometimes manifest as severe emergencies requiring prompt and extensive medical intervention. Urgent intervention is essential for effectively recognizing and managing these situations, as they have the potential to be life-threatening and can result in severe morbidity and mortality. Emergencies in IRDs can occur with different frequencies and manifestations, including nervous system issues, severe infections, thrombosis-emboli, renal crises, gastrointestinal issues, and cardiovascular events. The fact that these events can occur across different IRDs underscores the necessity for heightened awareness and readiness among healthcare professionals. The pathophysiologic mechanisms that cause rheumatic emergencies are complex and involve multiple factors. These emergencies frequently arise due to the interplay between the inflammatory characteristics of rheumatic diseases and different systemic triggers. Early detection and treatment can have a substantial impact on an individual's prognosis in cases of severe and life-threatening disorders that require prompt recognition. Rapid decision-making and urgent care are required to effectively address rheumatic emergencies, as well as the implementation of a diagnostic flowchart. This article provides an overview of the emergencies linked to IRDs, classifying and assessing them individually. This article aims to enhance healthcare professionals' knowledge and awareness of critical situations by examining current recommendations and pathophysiological information. Implementing standardized diagnostic and treatment methods, providing patient education, and conducting continuing research into the underlying mechanisms are essential for enhancing the management of these critical situations and improving patient outcomes.

Diagnosis and Management of Catastrophic Antiphospholipid Syndrome and the Potential Impact of the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria

Catastrophic antiphospholipid syndrome (CAPS) is a rare and life-threatening condition characterized by the persistence of antiphospholipid antibodies and occurrence of multiple vascular occlusive events. CAPS currently remains a diagnostic challenge and requires urgent treatment. The diagnosis of CAPS is made difficult by classification criteria used as diagnostic criteria in clinical practice, knowledge derived from retrospective data and case reports, confounding clinical and biological features, and its rapid onset and mortality. The absence of prospective studies of CAPS limits the strength of evidence for guideline treatment protocols. This comprehensive review summarizes the current understanding of the disease, and discusses how the 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria impact the definition and therapeutic management of CAPS, which is considered the most severe form of APS. The correct integration of 2023 ACR/EULAR APS classification criteria is poised to facilitate CAPS diagnosis, particularly in critical situations, offering a promising avenue for improved outcomes.

Antiphospholipid syndrome pathogenesis in 2023: an update of new mechanisms or just a reconsideration of the old ones?

Antibodies against phospholipid (aPL)-binding proteins, in particular, beta 2 glycoprotein I (β2GPI), are diagnostic/classification and pathogenic antibodies in antiphospholipid syndrome (APS). β2GPI-aPL recognize their target on endothelium and trigger a pro-thrombotic phenotype which is amplified by circulating monocytes, platelets and neutrophils. Complement activation is required as supported by the lack of aPL-mediated effects in animal models when the complement cascade is blocked. The final result is a localized clot. A strong generalized inflammatory response is associated with catastrophic APS, the clinical variant characterized by systemic thrombotic microangiopathy. A two-hit hypothesis was suggested to explain why persistent aPL are associated with acute events only when a second hit allows antibody/complement binding by modulating β2GPI tissue presentation. β2GPI/β2GPI-aPL are also responsible for obstetric APS, being the molecule physiologically present in placental/decidual tissues. Additional mechanisms mediated by aPL with different characteristics have been reported, but their diagnostic/prognostic value is still a matter of research.

What we know and what we don't know about catastrophic antiphospholipid syndrome

Catastrophic antiphospholipid syndrome (CAPS) is a severe condition with high mortality. Since its description in 1992, an important effort has been made to improve and disseminate knowledge on CAPS. Most of our current knowledge comes from the studies performed using the CAPS Registry, a database created in 2000 to gather as many cases as possible in order to better define this disease. It has demonstrated that this condition has multiple faces and is often triggered by a precipitating factor that leads to a thrombotic microangiopathy and cytokine storm involving almost any organ of the body. Analysis of the CAPS Registry has also shown that patients receiving anticoagulation, glucocorticoids and plasma exchange and/or IVIG have a better prognosis. However, there are still many unresolved questions. In this review we summarize what is known and what is still a matter of research in this condition.

Complement biomarkers in the antiphospholipid syndrome - Approaches to quantification and implications for clinical management

Complement is a major driver of antiphospholipid syndrome (APS) and a promising therapeutic target in refractory and catastrophic APS. Complement testing in APS is largely limited to research settings, and reliable, rapid-turnaround biomarkers are needed to predict those at risk for adverse clinical outcomes and most likely to benefit from complement inhibition. We review complement biomarkers and their association with thrombosis and obstetric outcomes, including: (i) complement proteins and activation fragments in the fluid phase; (ii) assays that evaluate complement on cell membranes (e.g. in vivo cell-bound complement fragments, hemolytic assays, and ex vivo 'functional' cell-based assays, and (iii) sequencing of complement genes. Current studies highlight the inconsistencies in testing both between studies and various aPL/APS subgroups, suggesting that either cell-based testing or multiplex panels employing a combination of biomarkers simultaneously may be most clinically relevant. Standardization of complement assays is needed to ensure reproducibility and establish clinically relevant applications.