Can Lyme Disease Be Mistaken for Dermatomyositis?
Rash and muscle weakness initially suggested dermatomyositis
Erythema migrans lesions later confirmed suspected Lyme disease
Antibiotic treatment led to recovery without immunosuppressants
Can Lyme disease be mistaken for dermatomyositis? Yes. Although uncommon, Lyme disease can occasionally mimic dermatomyositis, an autoimmune disease characterized by muscle weakness and distinctive skin rashes. Fatigue, weight loss, proximal muscle weakness, and inflammatory skin findings may initially suggest an autoimmune disorder rather than a tick-borne infection.
In this case report, an elderly woman with clinical features highly suggestive of dermatomyositis was ultimately diagnosed with Lyme disease after clinicians identified erythema migrans lesions and confirmatory serologic testing.
The clinical presentation was initially consistent with dermatomyositis (DM). “A 76-year-old female presented with fatigue, malaise, weight loss and progressive proximal muscle weakness after a flare-up of shoulder arthritis,” writes Novitch, a medical student at the Medical College of Wisconsin.
Why Doctors Initially Suspected Dermatomyositis
The patient’s physical findings strongly resembled dermatomyositis. “She had a heliotrope rash and a ‘Shawl sign,’ in addition to generalized cutaneous erythema with edema,” writes Novitch.
A heliotrope rash is a violet or bluish-purple discoloration around the eyes that is considered a classic feature of dermatomyositis. The patient also developed a widespread erythematous rash over the upper neck, shoulders, and upper back consistent with the characteristic Shawl sign.
Common symptoms of dermatomyositis include progressive muscle weakness, fatigue, weight loss, and characteristic skin rashes. Given these findings, the initial diagnosis of an autoimmune inflammatory muscle disease appeared reasonable.
How Doctors Diagnosed Lyme Disease
Because Lyme disease remained in the differential diagnosis, the physicians began empiric intravenous antibiotic therapy. The woman initially received IV Rocephin but rapidly deteriorated.
“The patient appeared toxic, became hypotensive and developed high-grade fever,” writes Novitch. She was transferred to the intensive care unit (ICU) for close monitoring.
While in the ICU, clinicians identified two target-shaped erythema migrans lesions over the left scapula.
“While in ICU, two target-shaped lesions were noted on her left scapula, highly suggestive of LD-related EM; they were not previously reported or observed,” writes Novitch.
Follow-up serologic testing confirmed Lyme disease.
The appearance of erythema migrans lesions together with positive serologic testing established the diagnosis and explained the patient’s dermatomyositis-like presentation.
The patient recovered after receiving five days of intravenous doxycycline combined with five days of IV Rocephin followed by two weeks of oral doxycycline.
“Her DM-like presentation showed an effective response to antimicrobial treatment, and therefore, required no steroids or immunosuppressants,” writes Novitch.
Why the Distinction Matters
Dermatomyositis is typically treated with corticosteroids and other immunosuppressive medications, whereas Lyme disease requires antibiotic therapy. Distinguishing between these conditions is important because the treatments differ substantially. In this patient, recognizing Lyme disease avoided unnecessary long-term immunosuppressive therapy and led to clinical recovery.
Lyme Disease as an Autoimmune Mimic
Novitch and colleagues point out that “LD could be a great mimicker of other autoimmune diseases like DM.”
This case illustrates how Lyme disease can occasionally resemble autoimmune disorders with muscle weakness, fatigue, rash, and systemic symptoms. Clinicians should consider Lyme disease in the differential diagnosis, particularly in patients from endemic areas or those with compatible clinical findings. Prompt recognition may help avoid unnecessary immunosuppressive treatment and lead to appropriate antibiotic therapy.
Frequently Asked Questions
Can Lyme disease be mistaken for dermatomyositis?
Yes. Although uncommon, Lyme disease can resemble dermatomyositis with muscle weakness, fatigue, rash, weight loss, and systemic symptoms.
How can doctors tell Lyme disease from dermatomyositis?
Doctors consider the patient’s history, possible tick exposure, characteristic skin findings such as erythema migrans, laboratory testing, muscle enzyme results, and response to antibiotic therapy. In uncertain cases, additional evaluation may be needed before starting immunosuppressive treatment.
What symptoms made this case resemble dermatomyositis?
The patient developed fatigue, weight loss, progressive proximal muscle weakness, a heliotrope rash, and a Shawl sign, all classic findings associated with dermatomyositis.
Clinical Takeaway
Lyme disease should remain part of the differential diagnosis in patients presenting with unexplained muscle weakness, inflammatory skin rashes, fatigue, and other findings suggestive of dermatomyositis, particularly in endemic areas.
Although dermatomyositis and Lyme disease require very different treatments, this case illustrates why Lyme disease should remain in the differential diagnosis when patients present with unexplained muscle weakness, rash, and systemic symptoms, particularly in endemic regions.
Related Articles
Learn more about conditions that can resemble Lyme disease and related neurologic complications.
Can Lyme disease mimic autoimmune disease?
Can Lyme disease be mistaken for shingles?
Can Lyme disease be associated with Guillain-Barré syndrome?
References
- Novitch M, Wahab A, Kakarala R, Mukerji R. The Emergence of a Forgotten Entity: Dermatomyositis-like Presentation of Lyme Disease in Rural Wisconsin. Cureus. 2018;10(5):e2608.
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
