[A new cause of acute transitory auriculoventricular block: Lyme disease].

A young man developed syncopal complete paroxysmal atrioventricular block (AVB) over a 36 hour period, on a background of 1st degree AVB which persisted for 6 weeks. During the 3rd week, electrophysiological studies showed an isolated prolonged AH interval. This episode followed skin and articular manifestations occurring one month after being bitten by a tick in Corsica. The clinical picture suggested Lyme's disease which was confirmed serologically. This condition transmitted bu Ixodes ricinus, a tick present in country districts, is due to spirochetal infection. It is characterized by a chronic migrating erythema, and may sometimes be complicated by severe AV conduction defects which are always regressive, as in our case.