We analyzed blood and cerebrospinal fluid samples of patients with myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS) to detect any potential paraneoplastic antibodies against the antigens of the central nervous system. Concurrently we used indirect immunofluorescence on mouse tissue (cerebellum, kidney, gastric mucosa) and Western blot. We detected antineuronal specific antibodies of IgG class with identical immunofluorescence and immunoblot pattern in two patients with myasthenia gravis and Lambert-Eaton’s myasthenic syndrome. The confirmation test with recombinant antigen (HuD) did not identify them as anti-Hu antibodies (ANNA-1). We consider them antineuronal atypical IgG antibodies of yet unknown pathophysiological relevance.

        Key words: myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS), paraneoplastic autoanti- bodies, immunofluorescence, immunoblot.