Lyme Disease and Related Tick-Borne Infections - Diseases with Similar Symptoms

Allergic Reaction to the Tick. If a rash, even ring-shaped, appears hours rather than days after a tick bite, it is most likely an allergic reaction to the tick, not a symptom of Lyme disease.

Other Insect Bites. Not every rash seen in regions where Lyme disease is common is caused by a tick. The bites of many insects and spiders can cause a skin reaction.

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Autoimmune Diseases

A number of autoimmune diseases have chronic and low-level symptoms that may be confused with either acute or chronic Lyme disease.

Systemic lupus erythematosus (SLE) produces a rash (usually on the face), flu-like symptoms, and arthritis, but they usually develop very slowly over time.
Rheumatoid arthritis or Reiter's syndrome causes pain, swelling, or stiffness of the joints that may be confused with post-Lyme syndrome.
Scleroderma has a limited form of the disease called morphea, which produces hard patches of skin. Some studies have even reported an association between B. burgdorferi and some cases of morphea. However, the evidence is weak and if it exists it is possibly limited to a specific variant in Europe and Asia. There is no association between severe scleroderma and Lyme disease.
In children, juvenile rheumatoid arthritis or rheumatic fever, which follows strep throat, should be considered.

Diseases Resembling Post-Lyme Syndrome

A number of conditions cause chronic fatigue and joint and muscle aches that resemble descriptions of post-Lyme syndrome.

Mononucleosis -- this virus infection is common in teenagers
Chronic fatigue syndrome (CFS)
Fibromyalgia

Depression

Depression that may be mistaken for post-Lyme syndrome is marked by physical symptoms, including persistent fatigue and vague aches and pains.

Meningitis

The early neurologic symptoms of Lyme disease (headache, stiff neck, and fatigue) can easily be mistaken for viral meningitis. Children with viral meningitis are more likely to have a higher fever. Patients with Lyme disease often have other symptoms, such as the bulls-eye rash.