A variety of signs and symptoms are associated with Lyme disease (an infection caused by a deer tick's bite). Some are specific only to Lyme disease itself, and others are similar to symptoms of different medical conditions. Accordingly, the signs and symptoms may differ depending on the stage of the disease. Lyme disease generally progresses in three stages:

• Early localized Lyme disease. This is distinguished by elevated red skin lesions called erythema migrans (EM) at the site of the tick bite, which is typically at the underarm, groin, back of the knees or waist. As bacteria spread in the bloodstream, so does the rash. Its appearance is made up of multiple rings, similar in appearance to a "bull's-eye."
  
  Almost all people with Lyme disease develop this symptom, even if they do not recall being bitten by a tick. EM usually appears within a window of about one week and lasts for several days. However, it can take as long as one month to appear and last for several weeks in some instances.
  
  Flu-like symptoms (e.g., fatigue, headache, muscle and joint pain, swollen lymph nodes) may also be present during early localized Lyme disease.
  
  
• Early disseminated Lyme disease. During this stage, the bloodstream spreads the bacteria to other areas of the body, sometimes inflaming tissues. Often the symptoms exhibited by people with this stage of Lyme disease are the first to be reported. Symptoms of early disseminated Lyme disease include:
  
• • Heart inflammation. People with untreated early disseminated Lyme disease may experience this or other related cardiac symptoms (e.g., pericarditis, heart block) although the occurrence is relatively uncommon.
    
    
  • Neurologic disorders. In rare cases, inflammation in the central nervous system may cause meningitis (inflammation of the tissue covering the brain and spinal cord) or encephalitis (inflammation of the brain) in people with early disseminated Lyme disease. These symptoms may be characterized by headache or a stiff neck. Other problems may also occur, such as numbness or weakness in limbs, peripheral neuropathy, partial paralysis, facial nerve palsy (Bell's palsy) or odd sensations.
    
    
• Late Lyme disease. Symptoms of late Lyme disease may not be apparent for several months or years after being bitten by an infected tick. However, these may be the first symptoms of the disease for some individuals, and may include:
  
• • Joint or muscle pain. This is common in people with late Lyme disease who have not been treated. Intermittent and sometimes chronic episodes of asymmetric arthritis (joint inflammation) occur frequently in people with this stage of the disease. Sometimes arthritis has also been seen in early stages.
    
    
  • Neurologic symptoms. A variety of neurologic symptoms (e.g., pain, impaired memory or judgment, odd sensations or numbness, temporary paralysis) can occur during late Lyme disease.
    
    
  • Skin symptoms. European Lyme disease (Lyme borreliosis) in its late phase may cause certain skin problems (e.g., lumps, patchiness, puffiness) on parts of the hands, feet, knees or elbows.

After Lyme disease has been successfully treated and eradicated, vague symptoms (e.g., headache, fatigue, joint pain) may persist. Collectively, this phenomenon is known as post-Lyme disease syndrome. Fibromyalgia, a chronic pain disorder, is common in people who experience post-Lyme syndrome, although why this occurs is not fully clear.