Lyme disease is caused by a tick-borne spirochaete, Borrelia burgdorferi. Infection may be asymptomatic, may cause only erythema migrans (spreading from the site of the tick bite) or may cause disseminated disease affecting many organs, including the nervous system. Infection with B burgdorferi is transmitted by ixodid ticks, which are found in many parts of the UK. Their activity is seasonal, with peaks in summer and early autumn. The risk of human infection mirrors tick activity, with peak periods in summer and early autumn, although patients may present with later-stage manifestations throughout the year.

A 53-year-old man presented in September 2004 with a 3-week history of pain in the left flank and lumbar region, associated with hypersensitivity in the left lower abdomen; 5 days before admission, the right side also became affected. Constipation and hesitancy of micturition, with preserved sensation, had been present for 3 days. No weakness in the legs, fever or rash was observed. The patient was a non-smoker and drank <30 units of alcohol a week. He was regularly exposed to the risk of tick bite owing to the area of residence and recreational activities, but he denied recent tick bites. Six years earlier, the patient had presented with erythema migrans, fever and a …