Antibody binding to neuronal surface in movement disorders associated with lupus and antiphospholipid antibodies

Aim Systemic lupus erythematosus is a multi-organ autoimmune disorder associated with autoantibodies of complex diversity. Antiphospholipid antibodies (aPL), which are commonly associated with lupus, create a pro-thrombotic tendency, but are also associated with non-thrombotic neurological features. Movement disorders are rare neuropsychiatric complications of lupus and antiphospholipid syndrome, and autoimmune and thromboembolic disease mechanisms have been proposed. Method We describe the clinical features, investigation findings, treatment, and outcome of six paediatric participants with movement disorders associated with lupus and/or aPL (six females, median age 13y, range 8-15). To examine the autoantibody hypothesis, we used a neuronal cell line with dopaminergic characteristics and measured serum antibody binding to neuronal cell-surface antigens using flow cytometry. For comparison with the six participants, we used serum from healthy individuals (n=12, six females, median age 11y, range 9-13) and children with other neurological diseases (n=13, seven females, median age 7y, range 2-15). Results Of the six participants, two had lupus only, two had lupus with aPL, and two had aPL only. The movement disorder was chorea in four and parkinsonism in two. All four participants with chorea had aPL and movement disorder relapses. The two participants with parkinsonism did not have aPL, but had a progressive course until rituximab or plasma exchange resulted in neuropsychiatric remission. All six participants demonstrated elevated serum antibody binding to neuronal cell-surface antigens compared with healthy individuals and those with other neurological diseases. Interpretation This report supports the association of chorea with aPL, but suggests a different autoimmune mechanism operates in lupus parkinsonism. The presence of antibody binding to neuronal cell-surface antigens supports a possible direct action of autoantibodies on neurons in patients with movement disorders associated with lupus and aPL.