Lyme Disease Misdiagnosed as Psoriatic Arthritis
SWOLLEN FINGERS—BUT TREATMENT ISN’T WORKING?
LYME DISEASE CAN MIMIC PSORIATIC ARTHRITIS
“The diagnosis made sense—but the treatment didn’t help.”
Lyme disease can present with joint swelling and inflammation that closely resemble inflammatory arthritis, including psoriatic arthritis.
Quick Answer: Lyme disease can mimic psoriatic arthritis, especially when symptoms such as dactylitis and joint swelling do not respond to standard treatment.
Clinical Insight: When inflammatory arthritis fails to improve with corticosteroids or disease-modifying therapies, Lyme disease should be reconsidered—particularly in endemic regions.
For a full overview of Lyme arthritis, including symptoms, diagnosis, and treatment, see our main guide.
When psoriatic arthritis treatment fails
A man in his 70s presented with dactylitis (severe swelling of the fingers), nail changes, and scalp psoriasis—leading to a diagnosis of psoriatic arthritis.
However, he did not respond to corticosteroids or disease-modifying antirheumatic drugs.
This lack of response raised concern that the diagnosis might be incorrect.
The diagnostic clue
A skin biopsy revealed histopathologic changes consistent with Lyme borreliosis, and laboratory testing showed IgG antibodies to Borrelia burgdorferi.
“To our knowledge, this is the first case describing asymmetrical dactylitis in Lyme borreliosis,” the authors reported.
The patient did not recall a tick bite but noted that his symptoms began several weeks after gardening.
This pattern—no known tick bite with delayed onset of symptoms—is common in Lyme disease.
Response to treatment
The patient was treated with penicillin.
Within one week, swelling improved.
After six months, his arthritis, tendon inflammation, soft tissue swelling, and skin findings had completely resolved.
This response supported Lyme disease as the underlying cause.
Why Lyme disease can be mistaken for psoriatic arthritis
Dactylitis is commonly associated with psoriatic arthritis but may also occur in other conditions, including Lyme disease.
Lyme borreliosis can involve joints, tendons, and skin—leading to overlapping clinical features.
These patterns contribute to Lyme disease misdiagnosis, particularly when symptoms are evaluated in isolation.
When to reconsider the diagnosis
Clinicians should consider Lyme disease when:
- Joint swelling does not improve with standard therapy
- Dactylitis or tendon inflammation is unexplained
- Symptoms follow outdoor exposure
- No clear response to rheumatologic treatment is observed
These diagnostic challenges reflect why Lyme disease can be difficult to diagnose.
Clinical takeaway
Lyme disease can closely mimic inflammatory arthritis, including psoriatic arthritis.
When treatment fails or symptoms do not follow typical patterns, clinicians should revisit the diagnosis and consider Lyme disease.
Recognizing these patterns early can lead to appropriate treatment and full recovery.
Frequently Asked Questions
Can Lyme disease look like psoriatic arthritis?
Yes. Lyme disease can cause joint swelling and dactylitis that resemble psoriatic arthritis.
What is dactylitis?
Dactylitis is severe swelling of the fingers or toes and is often seen in inflammatory arthritis.
Why is Lyme disease misdiagnosed?
Symptoms overlap with other conditions, and patients may not recall a tick bite.
What is a key warning sign?
Lack of response to standard arthritis treatment should prompt reconsideration of the diagnosis.
Related Articles
- Lyme disease mimics cellulitis
- Lyme arthritis symptoms in children
- TMJ arthritis and Lyme disease
- Lyme arthritis overview
References
- Steppat A, Skaarup Andersen N, Andreasen CM. Rare case of Lyme borreliosis in a patient presenting with dactylitis and skin rash. BMJ Case Reports. 2023;16:e253182.
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
As a Lyme literate Advocate. This is a very good share as I have read about this for years and watched a golfer suffer and treat by big pharma drugs purposely for arthritis instead of Lyme.
As one who possibly suffers from this I am encouraged that you spread the knowledge and educate on this easily mis diagnosed disease. Thank you.
I suffered with swollen hands, painful fingers. I finally started seeing a rheumatologist group. With xrays they determined I had wear and tear and said my blood didn’t carry the markers for RA but I had high inflammation and treated me for psoriatic arthritis. I took some pretty serious medicines for years. When they suggested I start using Humera, I quit seeing them. I had two friends who had developed Lymphoma. Twenty years forward in 2020 I became very sick, high fever, vomiting, chills, body aches. This was during COVID which really scared me. I also got these big round rashes all over my trunk and arms and legs. Two weeks after and the rash hadn’t gone away I went to a walk-in and being in Maine at the time, the PA took one look at me, asked me where I hurt that was new and immediately told me I had Lymes
She told me that she was prescribing 3 weeks of Doxycycline and said I’m not even going to test you yet because the tests show false negatives because it doesn’t show up for a while. I took the 3 weeks of Doxy and my wife and I started the research. Learning that sometimes more treatment is required. We found a practitioner in Maine who had been misdiagnosed as having MS when in fact it was Lymes. With the IGENIX testing it revealed I had a past infection in my life and that a new tick bite made me really sick. I had four co-infections. Its now 2023 and I’m still being treated. I lost all feeling in my legs, feet, hands. I was in bed for at least 8 months. I’ve had lots of antibiotic therapy including a pic line, Cefroxin, I’ve had neck surgery from a bad fall as my legs were getting weaker, I’ve had lots of rehab. LDN, special tinctures made by a naturalist in Maine
Its been so hard being in Florida where Lymes is never a consideration. I finally was able to convince my cardiologist to give me a pacemaker and eblation. I have had A-fib in my past and had two conversions. The 2nd conversion after open heart surgery replacing two valves and a cabbage bypass. When I got so sick in 2020 and with the very high fever my blood pressure dropped so low. Remember COVID was in its first stages. If I had gone to the hospital I would not have come out. My cardiologist was in Florida, I was in Maine. My A-fib came back and my blood pressure was all over the place. I lived with a heart rate running around 150 most of the time. I now have a heart rate around 80. I feel so much better, my cardiologist just shakes his head because he’s seen me go from an electric wheel chair, that I had to be tied in by the way, because I wasn’t able to feel my legs. I use a cane now. I still am taking certain supplements and tinctures, I still have fatigue and presently dealing with my lungs but I’ve come so far. I’m coming up on 79 and really glad to be alive. There were times though that I wished I could just have it over. The inflammation in my hands that I saw the rheumatologist for 20 years ago is gone. I don’t hurt like I used to. I’m thankful for that 2nd bite because I was getting pretty discouraged with the pain. My hand used to swell and turn red and shiny.
I have had patients who were sick for years with Lyme disease that had gone undetected until they get a tick bite or are newly infected with Lyme disease.
Hello,
I have a question about the tests being negative. I have Psoriatic Arthritis without the skin condition. I recently got tested for Lyme in a desperate attempt to get off biologics I did have tic bites when I was young, I am now 62, and my condition has steadily progressed, Psoriatic, Scoliosis, Degenerative disc, Osteoarthritis all basically at times same time. (?)
Can you please help me understand how, if my test result was negative, is there even a tiny number (amount) like .19? They only count it if it’s. 91 to 1.1 (I think 🤔). If I don’t have it, and they will not redo it, how IS THERE EVEN a SMALL number? Thank you,
Elaine Johnson
I have Lyme disease patient who never have a positive test. Patient vary in their antibody response to Lyme