Lyme disease is an infectious disease caused by the spirochete Borrelia burgdorferi. The course of the disease is divided into three stages, the second of which may include various types of peripheral nervous system disturbances. We report the case of a patient with persistent deficits caused by the prevalent involvement of the sciatic nerve, confirmed by electrophysiological and neuropathological findings. The most significant bioptic results were axonal degeneration and perivascular inflammation. Damage to a single peripheral nerve as the dominant clinical expression during the course of Lyme disease is an unusual finding that has been rarely described in the literature.