Misdiagnosis of Lyme disease is common. Diagnosis of Lyme disease is complicated by several factors:

• The bacteria that cause the illness are hard to detect with current lab tests. People often test positive for Lyme disease when in fact they have a different bacterial illness. Or they may test positive because they were infected with the bacteria at some point during their lives, but the infection may not be active and may not cause any illness. Also, they may test negative when they actually have been infected.
• Symptoms of Lyme disease sometimes closely resemble those of other illnesses. Chronic Lyme disease, for instance, has symptoms very similar to those of several other chronic illnesses, particularly juvenile idiopathic arthritis, fibromyalgia, and chronic fatigue syndrome. Treatment with antibiotics that are normally used to treat Lyme disease is not helpful for people with these other conditions.