Conditions Lyme Disease Can Mimic (And Why It’s Often Misdiagnosed)
Lyme symptoms can overlap with other illnesses
Pain, fatigue, and brain fog are not specific
The complete clinical pattern matters
Conditions Lyme disease can mimic include fibromyalgia, ME/CFS, multiple sclerosis, rheumatoid and other inflammatory disorders, peripheral neuropathy, migraine or vestibular disorders, POTS, and some psychiatric conditions. Because many symptoms overlap, Lyme disease may initially be attributed to another illness.
A 2023 Canadian study illustrates this diagnostic challenge. Researchers comparing people with presumptive Lyme disease with people who had Lyme-like chronic illnesses found similarly profound symptom and functional burdens. Symptom questionnaires did not clearly distinguish the groups.1
This does not mean that everyone with fibromyalgia, ME/CFS, neurologic symptoms, or another chronic illness has Lyme disease. It means that fatigue, widespread pain, brain fog, sleep disturbance, and reduced function are not specific enough by themselves to determine the underlying diagnosis.
Exposure history, the timing and evolution of symptoms, physical findings, appropriate laboratory testing, and alternative diagnoses all remain important.
Why Can Lyme Disease Resemble Other Conditions?
Lyme disease can affect several body systems. Depending on the stage and presentation, patients may develop musculoskeletal, neurologic, cardiac, dermatologic, or systemic manifestations.2
Some findings—such as an expanding erythema migrans rash, facial nerve palsy, painful radiculoneuritis, carditis, or objective swelling of a large joint—may provide stronger diagnostic clues.
The challenge becomes greater when the predominant complaints are nonspecific symptoms such as fatigue, widespread pain, headache, dizziness, poor sleep, or cognitive difficulty.
These symptoms occur in many illnesses.
In addition, Lyme disease testing has limitations, particularly during early infection before a detectable antibody response has developed.
The diagnosis therefore should not be based on a symptom checklist—or on one laboratory result considered in isolation.
What Did the Canadian Study Find?
Sanderson and colleagues studied 157 people in Eastern Canada with a range of chronic and complex illnesses. Participants were categorized as having presumptive Lyme disease, Lyme-like illness, other illnesses, or no reported illness.1
The Lyme-like group included people reporting diagnoses such as fibromyalgia syndrome, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), neurologic disorders, and rheumatic conditions.
Participants completed questionnaires measuring symptoms, health status, and functional impairment. Researchers also performed blinded two-tier IgG and IgM testing for antibodies to Borrelia burgdorferi.1
The pattern of symptoms and functional impairment was similarly profound in the presumptive Lyme disease and Lyme-like groups.1
In other words, symptom burden alone did not clearly separate patients considered to have Lyme disease from patients carrying other chronic illness diagnoses.
What Did Borrelia Testing Show?
The researchers found approximately 10% seroprevalence for both IgG and IgM across the study cohort. Seropositive participants were found both within and outside the presumptive Lyme disease category.1
Fibromyalgia was the most common individual diagnostic label among two-tier IgG-positive participants who did not report a previous Lyme disease diagnosis.1
That finding is interesting, but it needs to be interpreted carefully.
A positive antibody test demonstrates an immune response to Borrelia. It does not by itself establish when infection occurred, whether viable bacteria remain present, or whether Lyme disease is responsible for a patient’s current chronic symptoms.
The study was also cross-sectional and involved a selected group of people with complex chronic illnesses. Its approximately 10% seroprevalence should therefore not be interpreted as the prevalence of Lyme disease among all people with fibromyalgia, ME/CFS, or other chronic conditions.1
Common Conditions Lyme Disease May Resemble
Depending on the patient’s presentation, Lyme disease may enter the differential diagnosis alongside:
- Fibromyalgia
- Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)
- Multiple sclerosis and other neurologic disorders
- Peripheral neuropathy
- Rheumatoid and other inflammatory arthritis
- Migraine and vestibular disorders
- POTS and other forms of autonomic dysfunction
- Depression and anxiety disorders
- Other causes of chronic pain and fatigue
The reverse diagnostic error is also possible. A patient may have symptoms attributed to Lyme disease when another neurologic, rheumatologic, endocrine, sleep, psychiatric, infectious, or other medical condition better explains the illness.
Diagnostic overlap should therefore broaden the evaluation rather than predetermine its conclusion.
Symptoms That May Lead to Another Diagnosis
| Lyme disease symptom or pattern | Other diagnoses that may be considered |
|---|---|
| Widespread pain | Fibromyalgia or other chronic pain disorders |
| Severe fatigue | ME/CFS, post-viral illness, sleep or metabolic disorders |
| Brain fog | ME/CFS, sleep disorders, depression, or neurologic illness |
| Numbness, tingling, or burning pain | Peripheral neuropathy or neurologic disease |
| Dizziness or imbalance | Vestibular disorders, migraine, or autonomic dysfunction |
| Rapid heart rate or lightheadedness | POTS or other autonomic disorders |
| Joint pain | Inflammatory, rheumatologic, or orthopedic disorders |
| Mood or anxiety symptoms | Primary psychiatric illness, sleep disturbance, or other medical conditions |
None of these symptoms is specific to Lyme disease. Their diagnostic value depends on how they fit into the patient’s complete history and clinical presentation.
Fibromyalgia and ME/CFS
Fibromyalgia and ME/CFS provide particularly good examples of the diagnostic overlap highlighted by the Sanderson study.
Patients with these conditions may experience severe fatigue, widespread pain, sleep disturbance, cognitive difficulties, headaches, exercise intolerance, and substantial impairment in daily function.
Many of these complaints are also reported by patients with Lyme disease and by patients with persistent symptoms following Lyme disease.
The 2023 Canadian study found that participants considered to have presumptive Lyme disease and those with Lyme-like chronic illnesses had similarly substantial symptom and functional burdens. Their symptom questionnaires did not clearly distinguish the groups.1
The study does not demonstrate that Lyme disease causes fibromyalgia or ME/CFS. It demonstrates why symptoms alone may be insufficient to determine which diagnosis best explains an individual patient’s illness.
For a more detailed discussion, see Fibromyalgia and Lyme Disease: Can Lyme Disease Be Mistaken for Fibromyalgia?.
Neurologic Conditions Lyme Disease Can Resemble
Neurologic Lyme disease can produce manifestations involving the cranial nerves, nerve roots, meninges, and peripheral nervous system. Patients may experience facial weakness, severe radicular pain, headache, numbness, tingling, weakness, or other neurologic symptoms.
Other complaints—including dizziness, cognitive difficulties, headaches, sensory symptoms, and balance problems—may overlap with numerous neurologic conditions.
This can lead to evaluation for multiple sclerosis, migraine disorders, peripheral neuropathy, vestibular disease, or other neurologic illnesses before Lyme disease is considered.
However, neurologic symptoms alone do not establish Lyme disease. Neurologic examination, exposure history, appropriate testing, imaging or cerebrospinal fluid studies when indicated, and consideration of alternative diagnoses may all contribute to the evaluation.
For a deeper overview, see Neurologic Lyme Disease: Understanding the Nervous System Symptoms.
Rheumatologic and Pain Conditions
Lyme disease can also enter the differential diagnosis when patients present with musculoskeletal symptoms.
Lyme arthritis classically produces objective swelling of one or a few large joints, particularly the knee. Other patients may report muscle or joint pain without the characteristic swollen joint.
Depending on the presentation, patients may initially be evaluated for inflammatory arthritis, orthopedic disease, fibromyalgia, or other chronic pain conditions.
Conversely, widespread pain alone should not be assumed to represent Lyme disease. Rheumatologic, neurologic, orthopedic, metabolic, and other causes may require evaluation.
For more on pain patterns, see Lyme Disease Pain.
Fatigue and Chronic Illness
Fatigue is common in Lyme disease but is also one of the least specific symptoms in medicine.
Severe fatigue accompanied by brain fog, sleep disruption, pain, or exercise intolerance may resemble ME/CFS or other post-infectious illnesses. Similar symptoms may also occur with sleep disorders, endocrine disease, anemia, medication effects, depression, and numerous other medical conditions.
The Sanderson study reinforces this point: profound functional impairment was present in both presumptive Lyme disease and Lyme-like chronic illness groups.1
For more on this symptom, see Lyme Disease Fatigue: Why It Causes Crushing Exhaustion.
POTS and Autonomic Conditions
Some patients with Lyme disease or persistent symptoms after treatment report dizziness, rapid heartbeat, exercise intolerance, temperature dysregulation, gastrointestinal symptoms, fatigue, and cognitive difficulties.
These symptoms may overlap with POTS and other forms of autonomic dysfunction.
Because dizziness, palpitations, fatigue, and exercise intolerance have many possible causes, autonomic symptoms should be evaluated rather than automatically attributed to Lyme disease.
For a broader discussion, see Autonomic Dysfunction in Lyme Disease.
Psychiatric Symptoms and Lyme Disease
Patients with Lyme disease may experience mood changes, anxiety, sleep disruption, irritability, cognitive difficulties, or other neuropsychiatric symptoms.
These complaints are not specific to Lyme disease. Depression, anxiety, medication effects, sleep disorders, neurologic disease, chronic pain, and other medical illnesses can produce similar symptoms.
The clinical question is therefore not whether every psychiatric symptom is caused by Lyme disease. It is whether a broader medical illness may be contributing when psychiatric symptoms occur alongside compatible neurologic, systemic, or exposure-related findings.
Learn more in Neuropsychiatric Lyme Disease.
Why Lyme Disease May Be Missed
Several factors can make Lyme disease more difficult to recognize:
- The tick bite may never be noticed.
- An erythema migrans rash may be absent, atypical, or overlooked.
- Early antibody testing may be negative.
- Symptoms may involve several body systems.
- Nonspecific symptoms overlap with many other illnesses.
- An initial diagnosis may appear to explain part—but not all—of the clinical picture.
These challenges do not mean that Lyme disease should automatically replace another diagnosis. They mean that the differential diagnosis may need to remain open when the clinical course is not adequately explained.
Why a Positive Lyme Test Does Not Settle the Diagnosis
The Sanderson study also illustrates the opposite diagnostic problem: Borrelia antibodies were identified across diagnostic categories.1
Antibody testing measures an immune response rather than directly demonstrating that viable organisms are responsible for current symptoms.
A positive result therefore needs to be interpreted alongside the patient’s symptoms, exposure history, previous Lyme disease, treatment history, physical findings, and alternative explanations.
Likewise, a negative antibody test obtained early in infection may occur before antibodies have reached detectable levels.
Neither symptoms nor serology should be interpreted without clinical context.
When Should Lyme Disease Be Reconsidered?
Reconsideration may be appropriate when the complete clinical picture raises reasonable suspicion for Lyme disease, particularly when:
- There has been plausible tick exposure.
- Symptoms began after an unexplained acute illness.
- An expanding rash may have occurred.
- Objective joint swelling develops.
- Facial palsy, meningitis, radicular pain, or other compatible neurologic findings occur.
- Symptoms evolve in a way the existing diagnosis does not adequately explain.
- Initial testing was performed very early in the illness.
At the same time, persistent unexplained symptoms should prompt consideration of diagnoses other than Lyme disease as well.
For more on this diagnostic challenge, see Lyme Disease Misdiagnosis: Why It Happens and What to Know.
Frequently Asked Questions
What diseases can Lyme disease mimic?
Lyme disease may resemble fibromyalgia, ME/CFS, some neurologic and rheumatologic disorders, peripheral neuropathy, migraine or vestibular disorders, POTS, and psychiatric conditions. The degree of overlap depends on the patient’s particular symptoms and manifestations.
Can Lyme disease be mistaken for fibromyalgia?
Yes. Both can involve widespread pain, fatigue, sleep disturbance, headaches, and cognitive difficulties. However, symptom overlap does not mean fibromyalgia is caused by Lyme disease. Exposure history, clinical findings, laboratory testing, and alternative diagnoses should be considered.
Can Lyme disease look like ME/CFS?
Yes. Lyme disease and ME/CFS can both involve severe fatigue, cognitive difficulties, sleep problems, pain, and impaired function. These symptoms alone cannot determine which condition is responsible.
Can Lyme disease look like multiple sclerosis?
Some neurologic manifestations of Lyme disease may resemble symptoms seen in multiple sclerosis or other neurologic disorders. Neurologic symptoms have many potential causes, so appropriate neurologic and infectious disease evaluation is important.
Does a positive Lyme test prove Lyme disease is causing chronic symptoms?
No. A positive antibody test demonstrates an immune response to Borrelia but does not by itself establish that active infection is responsible for current symptoms. Results need to be interpreted in the complete clinical context.
When should Lyme disease be reconsidered?
Lyme disease may deserve reconsideration when there is plausible tick exposure, a previous compatible rash or acute illness, objective neurologic or joint findings, an early negative test, or an evolving clinical picture that is not adequately explained by the existing diagnosis.
Clinical Takeaway
Lyme disease can resemble a wide range of chronic, neurologic, rheumatologic, pain, fatigue, autonomic, and psychiatric conditions because many symptoms cross diagnostic boundaries.
The 2023 Canadian study provides contemporary evidence of this overlap. People categorized as having presumptive Lyme disease and those with Lyme-like chronic illnesses reported similarly substantial symptom and functional burdens.1
The study does not show that these other conditions are actually Lyme disease. Instead, it demonstrates why symptoms alone may not be enough to distinguish complex chronic illnesses.
A thoughtful evaluation considers possible tick exposure, the timing and evolution of illness, objective findings, appropriate laboratory testing, previous diagnoses and treatment, and alternative explanations.
The goal is not to assume Lyme disease—or to dismiss it prematurely—but to determine which diagnosis or combination of diagnoses best explains the individual patient’s illness.
Related Articles
These articles provide more detail on the major diagnostic overlaps discussed above:
Fibromyalgia and Lyme Disease: Can Lyme Disease Be Mistaken for Fibromyalgia?
Lyme Disease Misdiagnosis: Why It Happens and What to Know
Lyme Disease Test Accuracy: Timing, Limitations, and Clinical Diagnosis
Neurologic Lyme Disease: Understanding the Nervous System Symptoms
Lyme Disease Fatigue: Why It Causes Crushing Exhaustion
References
- Sanderson VP, Miller JC, Bamm VV, Tilak M, Lloyd VK, Singh-Ranger G, Wills MKB. Profiling disease burden and Borrelia seroprevalence in Canadians with complex and chronic illness. PLoS One. 2023;18(11):e0291382. doi:10.1371/journal.pone.0291382.
- Shea J. Physical therapist recognition and referral of individuals with suspected Lyme disease. Phys Ther. 2021;101(8):pzab128. doi:10.1093/ptj/pzab128.
This article is for educational purposes only and is not a substitute for individualized medical advice, diagnosis, or treatment.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
