Lyme Disease Mimics Autoimmune Disorder in Elderly Woman
Lyme disease can mimic autoimmune disorders such as dermatomyositis—leading to potential misdiagnosis and delayed treatment.
A case report highlights a 76-year-old woman who presented with fatigue, malaise, weight loss, and progressive proximal muscle weakness following a flare of shoulder arthritis.
Her clinical presentation was consistent with dermatomyositis (DM), an autoimmune inflammatory muscle disease.
Dermatomyositis-Like Presentation
The patient exhibited classic features of DM, including a heliotrope rash and a “shawl sign.”
A heliotrope rash is a violet discoloration of the skin, often seen around the eyes. The shawl sign refers to a widespread erythema over the neck, shoulders, and upper back.
These findings strongly suggested an autoimmune diagnosis.
Clinical Deterioration and Diagnostic Clues
Based on clinical suspicion of Lyme disease, the patient was started on empiric intravenous antibiotics.
Despite treatment, she initially worsened—developing hypotension, high fever, and signs of systemic illness requiring ICU care.
While hospitalized, clinicians identified two target-shaped lesions consistent with erythema migrans, which had not been previously noted.
Follow-up serologic testing confirmed Lyme disease.
Treatment and Recovery Without Immunosuppression
The patient improved with antimicrobial therapy, including intravenous doxycycline and ceftriaxone followed by oral doxycycline.
Her dermatomyositis-like symptoms resolved without the need for steroids or immunosuppressive therapy.
This outcome supports an infectious rather than autoimmune etiology.
Why Lyme Disease Can Mimic Autoimmune Disorders
Lyme disease is known as a clinical “great imitator.” It can resemble autoimmune, neurologic, and rheumatologic conditions.
Failure to recognize this overlap may lead to inappropriate treatment with immunosuppressive medications.
As the authors note, Lyme disease can mimic autoimmune disorders such as dermatomyositis, emphasizing the importance of considering infection in the differential diagnosis.
Clinical Takeaway
Lyme disease can mimic autoimmune disorders like dermatomyositis. Consider tick-borne infection before initiating immunosuppressive therapy—especially in endemic regions.
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
