A controlled study of serum anti-locus ceruleus antibodies in REM sleep behavior disorder

The newly identified association of human nonnarcoleptic rapid eye movement (REM) sleep behavior disorder (RBD) with human leukocyte antigen (HLA) DQw1 class II genes raises the possibility that RBD may arise from autoimmune mechanisms. Two recent case reports involving postmortem brain stem histochemical analyses in elderly males with RBD identified severe monoaminergic cell loss in the locus ceruleus (LC). Thus, we designed a study to detect anti-LC antibodies in RBD. Ten Caucasian males (mean age, 66 years) with polygraphically confirmed RBD (n = 5, idiopathic RBD; n = 5, RBD with Parkinson's disease), but without narcolepsy, idiopathic hypersomnia, or autoimmune disease, were recruited for this study, along with 10 Caucasian male controls (mean age, 63 years) without a history of sleep disorder or autoimmune disease. In a blinded design, sera from the RBD patients and their controls were tested against human LC and other brainstem neurons. Brainstem tissue was obtained from autopsies of neurologically normal individuals. The presence of anti-LC antibodies was examined using immunohistochemistry on brainstem sections. Sections incubated with sera from normal individuals and sera from patients with paraneoplastic antineuronal antibodies (anti-Hu and anti-Ri) were used as controls. No reactivity with LC or any other brainstem area was identified with sera from either RBD patients or their controls, or from the other group of normal individuals. In contrast, sera from patients with paraneoplastic anti-Hu and anti-Ri antibodies reacted strongly with nuclei of LC and other brainstem neurons, sparing the nucleoli, and reacted to a lesser extent with the cytoplasm of these neurons. Therefore, it is unlikely that human RBD is associated with anti-LC antibodies. However, an autoimmune process in RBD has not been excluded by this study.