Psychoses in three cases with myasthenia gravis and thymoma--proposal of a paraneoplastic autoimmune neuropsychiatric syndrome.

Three patients with neuropsychiatric symptoms (NPSs) associated with thymoma, high serum titers of antiacetylcholine receptor (AchR) antibody and generalized myasthenia gravis (MG) are reported. The NPSs were homogeneous; (1) Altered consciousness as manifested by dreamy state with paramnesia, (2) psychosensory symptoms (the sudden change of senses of smell and taste with behavior abnormalities, auditory and visual hallucinations, déjà experiences, microteleopsia and derealization), (3) cognitive disturbances (recent memory loss with compulsive behaviors), (4) emotional disturbances (agitation, fear and anger), and (5) psychotic symptoms (secondary delusions and hallucinations) were characteristic. The NPSs preceded by several months to years the onset of MG, and thereafter they were closely related to worsening and relapse of MG. A typical patient showed repeatedly abnormal electroencephalograms (EEG) indicative of cerebral dysfunction. Another showed improvement of the NPSs after thymectomy and immunosuppressive therapy. The organicity of the phenomenology of psychoses with the same NPSs was suggested and it appears to comprise a unique paraneoplastic syndrome by central autoimmune mechanism. We proposed an autoimmune psychiatric syndrome and the genesis of psychosis due to the central cholinergic dysfunction in MG.