Lyme disease can sometimes be confused with other conditions, such as rheumatoid arthritis (RA). Both Lyme disease and RA can become debilitating if not treated.

When treated, Lyme arthritis symptoms usually go away. On the other hand, treatment for RA can slow the progression of the disease, but not cure it.

How can you tell which of these you have? In brief:

  • If your arthritis symptoms are in one joint and intermittent, it may be Lyme.
  • If your arthritis is in joints on both sides of your body, and pain and stiffness occur every morning, it may be RA. Having RA risk factors makes a diagnosis of RA more likely.

Lyme

Lyme disease has a known cause. It’s transmitted by the spiral-shaped bacteria Borrelia burgdorferi, which is carried by blacklegged deer ticks.

Lyme is difficult to diagnose because its wide range of symptoms mimic those of many other ailments.

If treated early with antibiotics, it can be cured. If Lyme is undiagnosed and treated late, the symptoms can become much worse, though it’s still treatable.

RA

RA’s cause isn’t known. It’s a chronic inflammatory disease affecting the lining of your joints and is thought to be a systemic autoimmune disease.

RA results in damage to your cartilage and bone that can become progressively worse if not diagnosed and treated early. The damage is irreversible. Treatment includes anti-inflammatory drugs and sometimes antibiotics.

Lyme risks

The basic risk factor for Lyme disease is living in, working in, or visiting an area where there are deer and ticks.

About 60 percent of people with untreated Lyme develop arthritis. For most people, Lyme arthritis clears up once it’s treated with antibiotics. But in some cases, the Lyme arthritis doesn’t respond to antibiotics. One small study found that as many as one-third of those with Lyme arthritis were not responsive to antibiotics.

In addition, some people develop arthritis post-Lyme, including inflammatory arthritis such as RA. A 2000 study estimated that about 10 percent of adults with Lyme arthritis develop inflammatory arthritis that doesn’t respond to antibiotics.

The role of inflammatory antibodies in arthritis and Lyme isn’t well understood. In a 2016 French study of 814 people with recently diagnosed inflammatory arthritis, only 11.2 percent had IgM antibodies, which are a risk factor for RA.

One study found that 10 to 20 years after Lyme arthritis, more than 50 percent of people still had positive IgM or IgG antibody responses to the Lyme bacteria. One-third of people with early Lyme disease also had positive antibody responses after 10 to 20 years.

Lyme as an RA risk

Once you have Lyme, it’s a risk factor for later developing RA and other types of inflammatory arthritis, such as psoriatic arthritis (PsA) or peripheral spondyloarthritis.

In a 2016 study, about one-third of the participants who had Lyme arthritis later developed an inflammatory arthritis like RA.

If you see a Lyme rash and get treated immediately with a sufficient course of antibiotics, it’s unlikely that you’ll later have Lyme arthritis. But many people don’t see the tick, don’t have a Lyme rash, and go undiagnosed.

RA risks

Having a high level of IgM antibodies is a risk factor for RA. These presence of these antibodies, known as rheumatoid factors (RF), can result in an immune response that attacks healthy tissue. IgM antibodies are not well understood, and they are also found in people with other infections.

Another marker for RA is having anti-cyclic citrullinated peptide (anti-CCP) antibodies in your blood.

Specific risk factors for RA include:

  • Smoking. This is a strong risk factor for RA, especially for more severe RA.
  • Obesity. This is especially significant in people diagnosed with RA under age 55.
  • Family history of autoimmune disease.
  • Female sex. Women are two to three times more likely to develop RA than men.
  • Occupational exposure to dust and fibers.
  • Genes. RA isn’t inherited, but you may have a genetic susceptibility that increases your risk of developing RA.
  • Hormones. Hormonal and environmental factors, including infections and trauma, may be involved.

It’s interesting that moderate alcohol intake may reduce the risk of RA.

Lyme symptoms

Lyme arthritis symptoms include achy, stiff, or swollen joints. Usually only one joint is affected — most often a knee. Smaller joints or tendons or bursae may also be affected. The arthritis pain may be intermittent.

Lyme has many other symptoms in addition to arthritis. These can include:

  • an initial bull’s-eye or irregular red rash
  • fatigue
  • flu-like symptoms
  • night sweats
  • cognitive decline
  • neurological problems such as trouble balancing or Bell’s palsy
  • sensitivity to light
  • cardiac disease (carditis)

RA symptoms

Early symptoms of rheumatoid arthritis include:

  • joint stiffness on both sides of the body, especially in the morning or after inactivity
  • swollen, tender, or warm joints
  • smaller joint involvement, such as fingers and toes
  • decreased range of motion
  • fatigue
  • loss of appetite

About 40 percent of people with RA have symptoms that don’t involve the joints. RA can seriously affect your eyes, skin, heart, and lungs.

LymeRA
Joint involvement•Usually on one side only
•Large joints involved (most often a knee)
•May impact more than one joint
Usually hands, feet, and wrists on both sides (bilateral)
Other symptomsMany diverse symptoms that mimic those of other diseasesGeneral feeling of unwellness
Diagnosis•Standard tests not always accurate
•Often done by symptoms and response to antibiotics
Can be difficult, especially when there’s a history of Lyme
Duration of symptomsIntermittent and variableMay fade and flare
PainMild to severe•Mild to severe
•Joint stiffness for more than an hour in the morning
Antibiotic responseIn most cases, symptoms respondSometimes RA responds to antibiotics, but this isn’t understood and not FDA-approved
Infection involvementTick bite sometimes with coinfectionsSuspected, but not proven
OtherCan be severe if not treatedRisk factors may include smoking, exogenous hormonal use, reproductive factors, family history of autoimmune diseases, and obesity

Lyme and Lyme arthritis

Treatment for Lyme is a course of antibiotics for at least one month, if the tick bite or a Lyme rash is noticed. Lyme arthritis is not likely to occur after antibiotics are given. Doxycycline is usually the initial antibiotic prescribed.

Lyme arthritis is sometimes the first symptom of Lyme. A course of antibiotics will often clear up the arthritis symptoms.

Antibiotics may be given orally or intravenously, depending on the severity of Lyme symptoms.

When Lyme arthritis occurs in the post-infection stage of Lyme, anti-inflammatory drugs such as methotrexate may be used.

RA

The standard treatment for RA includes anti-inflammatory agents such as:

  • nonsteroidal anti-inflammatory drugs
  • steroids
  • conventional or biologic disease-modifying anti-rheumatic drugs (DMARDS)

Both Lyme and RA have a better outcome the sooner they are diagnosed and treated.

Lyme

Most people don’t see the initial Lyme rash, and the diversity of possible symptoms makes diagnosis difficult. If you have symptoms of arthritis and could have been bitten by a tick, see your doctor to rule out Lyme. It’s best to find a Lyme-aware doctor.

RA

RA also can be difficult to diagnose. If your joints regularly are stiff for an hour or more after you wake up, see your doctor. It could be RA.