SP0165 The complex interplay between systemic lupus erythematosus and antiphospholipid syndrome

Abstract

The antiphospholipid syndrome (APS) was first described in the 1980's. It is diagnosed when antiphospholipid antibodies (aPL) i.e. anti-cardiolipin (aCL), antib2Glycoprotein- I (ab2GPI) or positivity in the functional lupus anticoagulant test (LA) occur together with any type of thrombosis (e.g. myocardial infarction(MI), stroke, venous or microvascular thromboses) or obstetric complications(.5 aPL recognise protein co-factors, most importantly the scavenger protein b2GlycoproteinI (b2GPI), that bind to membrane phospholipids. It is not fully understood how complexes of b2GPI and anti-b2GP1 antibodies initiate a pro-thrombotic state, but activation of platelets, endothelial cells and the complement cascade are associated features. Approximately 80% of APS patients are women, many are young and severely ill. There is a considerable overlap between APS and SLE. Approximately 30%-40% of SLE patients are aPL positive but only about half of them develop clinical symptoms fulfilling the APS classification criteria. Several prospective studies have demonstrated that aPL are predictive of vascular events in patients with SLE. Though conflicting results exist, we have not noted positive associations between aPL and accelerated atherosclerosis in SLE, rather we believe that it is the pro-thrombotic state, which is the major cause of vascular events in the aPL positive SLE subgroup. Microvascular disease is an often unrecognised and difficult to diagnose feature in the aPL positive SLE subgroup. We have noted that up to 15% of patients diagnosed with nephritis have microvascular pathology in accordance with APS nephropathy in renal biopsies. The aPL positive SLE subgroup has also been demonstrated to have a more rapid accrual of damage, where in addition to vascular damage neuropsychiatric damage makes a notable contribution. When investigating primary APS patients, we and others have noted traits that are normally seen and attributed to SLE, such as low platelets, complement consumption, a low grade of systemic inflammation and even low titers of anti-DNA antibodies. Thus, the distinction between these two groups, APS secondary to SLE and primary APS, is not always clear.