Diseases with Similar Symptoms:

Many other illnesses can mimic various features of Lyme disease. Depending on the symptoms, a doctor may be able to perform the evaluations necessary to rule out other conditions.

Ruling Out Other Tick-Borne or Spirochete Infections

Other infections can produce fever, headache, muscle aches, fatigue, and some of the neurologic or cardiac features of early Lyme disease. Some are transmitted by the same tick as Lyme disease.

Co-Infections Transmitted by the Ixodes Tick. Babesiosis and human granulocytic anaplasmosis (HGA) are transmitted by the same tick that carries Lyme disease. People may be co-infected with one or more of these infections, all of which can cause flu-like symptoms. If these symptoms persist and there is no rash, it is less likely that Lyme disease is present. Still, diagnosing a co-infection is difficult.

Other Spirochete Infections. Leptospirosis is a spirochete infection spread through animals or contaminated water that most often affects young people during the summer or fall.

Other Tick-Borne Infections. A number of other tick-borne diseases may resemble Lyme disease, although they are more common in parts of the U.S. where Lyme disease is less prevalent.

• Tick-borne relapsing fever (TBRF), a flu-like illness that occurs in mountainous areas of the West during the summer, may be misdiagnosed as Lyme disease. The antibiotic doxycycline may be prescribed to patients who have been bitten by ticks suspected of carrying TBRF, to help prevent development of the disease.
• Rocky Mountain spotted fever, which is also transmitted by ticks, is most prevalent in the south central and southeastern parts of the United States, but occurs throughout North and South America. The most characteristic symptom is a spotty rash that appears 5 - 10 days after infection. The disease is caused by ticks that carry the bacterial organism Rickettsia rickettsii, and is considered the most severe tick-borne illness in the United States. Unlike Lyme disease, which is rarely fatal, Rocky Mountain spotted fever causes death in 10% of all cases. Recent outbreaks of Rocky Mountain spotted fever have been linked to increases in wild dog populations.
• A tick-borne infection called by human monocyte ehrlichiosis (HME), carried by the Lone Star tick, strongly resembles Lyme disease, including a similar rash. It is not caused by the Lyme spirochete, however, and has been identified in patients who live in the southern United States.

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.

Autoimmune Diseases

A number of autoimmune diseases have chronic and low-level symptoms that may be confused with 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 syndrome causes pain, swelling, or stiffness of the joints that may be confused with post-Lyme disease 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 Disease Syndrome

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

• Mononucleosis (this viral infection is common in adolescents)
• Chronic fatigue syndrome (CFS)
• Fibromyalgia
• Depression (may include 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 bull's-eye rash.