Antiphospholipid antibody syndrome and polymyalgia rheumatica/giant cell arteritis

The Pathophysiology of The Antiphospholipid Syndrome: A Perspective From The Blood Coagulation System

The antiphospholipid syndrome (APS), a systemic autoimmune disease characterized by a hypercoagulability associated to vascular thrombosis and/or obstetric morbidity, is caused by the presence of antiphospholipid antibodies such as lupus anticoagulant, anti-β-2-glycoprotein 1, and/or anticardiolipin antibodies. In the obstetrical APS, antiphospholipid antibodies induce the production of proinflammatory cytokines and tissue factor by placental tissues and recruited neutrophils. Moreover, antiphospholipid antibodies activate the complement system which, in turn, induces a positive feedback leading to recruitment of neutrophils as well as activation of the placenta. Activation of these cells triggers myometrial contractions and cervical ripening provoking the induction of labor. In thrombotic and obstetrical APS, antiphospholipid antibodies activate endothelial cells, platelets, and neutrophils and they may alter the multimeric pattern and concentration of von Willebrand factor, increase the concentration of thrombospondin 1, reduce the inactivation of factor XI by antithrombin, increase the activation of factor XII, and reduce the activity of tissue plasminogen activator with the subsequent production of plasmin. All these effects result in less permeable clots, denser, thinner, and with more branched fibrin fibers which are more difficult to lysate. As a consequence, thrombosis, the defining clinical criterion of APS, complicates the clinical course of the patient.

Antiphospholipid antibody syndrome and autoimmune diseases

The arbitrary division between antiphospholipid antibody syndrome and secondary antiphospholipid antibody syndrome has not proven useful. Antiphospholipid antibodies in the absence of antiphospholipid antibody syndrome often occur as epiphenomena in many autoimmune diseases. They are very common in systemic lupus erythematosus. Antiphospholipid antibody syndrome is a significant comorbidity in lupus but is uncommon in Sjögren's syndrome, rheumatoid arthritis, scleroderma, and systemic vasculitis. Evidence is growing that antiphospholipid antibodies may have a pathogenic role in pulmonary hypertension and accelerated atherosclerosis of autoimmune diseases.

Primary systemic vasculitis: treatment of difficult cases

The primary systemic necrotizing vasculitides are a severe group of diseases, which untreated have a high mortality. The majority respond to treatment with high dose steroids and cyclophosphamide, however a significant proportion of those treated suffer morbidity due to the side effects of these agents, and a number of patients are refractory to treatment. We review and discuss alternative and emerging treatment options for patients who fail or cannot tolerate conventional therapy. An interesting subgroup of patients with systemic vasculitis and antiphospholipid antibodies provides an additional diagnostic and therapeutic challenge. We review what is known about this subgroup, and suggest screening for antiphospholipid antibodies in all patients with systemic vasculitis.

Prevalence of the antiphospholipid syndrome in primary systemic vasculitis

BACKGROUND

The antiphospholipid (APS or Hughes') syndrome, anticardiolipin antibodies (aCL), and the lupus anticoagulant (LA) are associated with systemic lupus erythematosus, malignancy, infection, and drugs. It has been described in patients with primary systemic vasculitis (PSV).

OBJECTIVE

To determine the prevalence of APS in patients with PSV attending a vasculitis clinic and the prevalence of patients with positive aCL and/or the LA who do not fulfil the classification criteria for APS.

METHODS

All case notes of patients attending the vasculitis clinic over a 12 month period were reviewed. Outpatients and inpatients were both included and were assessed for features of the APS and presence of aPL. Patients with positive aCL or LA tests were classified according to the significance of these results.

RESULTS

Of 144 patients with PSV, 25 had positive aCL or LA on at least one occasion, representing a point prevalence of 17%. Of these, nine had definite APS (classified by the Sapporo criteria) and a further four patients had clinical and serological features of APS, although insufficient to satisfy the Sapporo criteria. Twelve had only positive aPL.

CONCLUSION

The antiphospholipid syndrome, aCL, and the LA may occur in association with PSV.

Primary versus secondary antiphospholipid syndrome: is this lupus or not?

Antiphospholipid syndrome is a hypercoaguable state characterized by recurrent venous and/or arterial thrombosis and/or pregnancy complications of fetal loss, pre-eclampsia, or eclampsia in the presence of antiphospholipid antibodies. It was first described in the setting of systemic lupus erythematosus and subsequently recognized to also exist as an independent condition and in conjunction with a variety of other autoimmune, infectious, and malignant illnesses. These diseases have been called primary antiphospholipid syndrome and secondary antiphospholipid syndrome. However, the two conditions can have significant overlapping features. This paper reviews the similarities and the differences between the two conditions.