Lyme disease is caused by a bacterium of Borrelia sp typically transmitted by tick bites.
Lyme disease has three stages: early localised disease, early disseminated disease and late disease. In the first stage, there is a bump and a small rash; these disappear after a couple of days. There may be a necrotic centre, but rash of erythema migrans develops a few days later and this may last up to thirty days. During this phase the patient may (in approximately 25% of cases) be febrile, have headaches, myalgia and arthralgia, fatigue and lymphadenopathy, but these symptoms may disappear.
The second stage occurs within days to weeks if the disease is untreated. The headaches are severe. Aseptic meningitis and Bell’s palsy (both usually in children), lymphocytomas (painless bluish-red nodules usually on the ear, scrotum and nipples, again most commonly in children), sensory and motor meningoradiculitis (in 85% of adults), arthritis, more generalised areas of erythema migrans, atrioventricular block, dizziness and persistent fatigue may all occur.
The third stage includes chronic pain from large joint oligoarthritis (almost always involving the knee), a marked neutrophilia, acrodermatitis chronica atrophicans (bluish-red patches on the extremities lasting up to ten years) and peripheral neuropathy. Rarely, slowly progressive encephalomyelitis or radiculomyelitis resulting in spastic ataxia has been noted.