Case of a 31 years old woman suffering from I and II type atrioventricular heart block, acute exogenic psychosis, intermittent type of fever and arthritis of right knee was described by the authors. The non typical clinical picture, the extremely elevated erythrocyte sedimentation rate and the exogenic type of psychosis caused differential diagnostic difficulties. Besides polysymptomatic autoimmune disorder, Lyme disease as emerged although there were no data of vector bite. In the consequence of steroid and combined antibiotic treatment the patient became immediately apyretic and the sedimentation rate returned to the normal limit. The psychotic symptoms have disappeared only two weeks following Ceftriaxon's and Doxycyclin's management. The high titer Borrelia seropositivity reserved to apply the diagnosis of Lyme disease.