Do all antiphospholipid antibodies confer the same risk for major organ involvement in systemic lupus erythematosus patients?

Objective We aimed to investigate the association between the different antiphospholipid antibodies (aPL) and both systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) manifestations. Methods Patients from the RELESSER registry, a Spanish retrospective, cross-sectional, forty-five hospital registry of adult SLE patients, were included. Results Out of a total of 3,658 SLE patients, 1372 were aPL positive (555 of them fulfilled criteria for APS). All aPL types showed a negative association with cutaneous SLE manifestations. Lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) were both associated with haematological, ophthalmological and neuropsychiatric manifestations. IgG isotypes were associated with a higher risk of lupus manifestations compared with IgM. We found that the risk of neuropsychiatric and ophthalmological manifestations significantly increased with a higher number of positive aPL whereas the risk of cutaneous symptoms showed a negative correlation. All types of aPL, and more strongly LA, were associated with non-criteria antiphospholipid syndrome (APS) manifestations such as thrombocytopenia and haemolytic anaemia. Moreover, LA and aCL (particularly IgG isotype) were also associated with Libman-Sacks endocarditis and cognitive impairment. This association was stronger with more than one positive aPL. All types of aPL were also associated with classic APS manifestations, although LA, IgG isotypes, and patients with more than one aPL displayed a higher risk. Conclusion There is a hierarchy for aPL and the risk of APS and SLE manifestations. aCL, and especially LA, confer a higher risk for major organ involvement in SLE. IgG isotypes seem to have a more important role. The load of aPL confer a higher risk for APS and certain SLE manifestations.