Rheumatoid Arthritis: Causes, Diagnosis, and Treatment

Epidemiology

Rheumatoid arthritis affects roughly 0.5-1% of the world population, making it one of the most common autoimmune diseases. In Brazil, an estimated 2 million people live with the condition.

RA is 2 to 3 times more common in women, suggesting hormonal influence. Risk factors include family history (3-5 times higher risk in first-degree relatives), smoking (the most strongly linked environmental factor), periodontal infections, and changes in the gut microbiota. Genetics account for 50-60% of the risk, with HLA-DRB1 (shared epitope) being the main associated gene.

Pathophysiology

In RA, the immune system loses the ability to distinguish the body's own tissues (self) from invaders. The synovial membrane, which normally is a thin layer that produces joint fluid, becomes the principal target of the autoimmune attack.

RA pathophysiology: normal joint vs. RA — T- and B-cell infiltrate, synovial hyperplasia (pannus), bone erosion, and cartilage destruction

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Immune Cascade

The disease begins with activation of CD4+ T lymphocytes that recognize autoantigens in the joints. These T lymphocytes activate B lymphocytes, which produce autoantibodies such as rheumatoid factor (RF) and anti-CCP antibodies (anti-cyclic citrullinated peptide antibodies).

The inflamed synovial membrane (synovitis) hypertrophies and forms an invasive tissue called pannus, which erodes cartilage and subchondral bone. Cytokines such as TNF-alpha, IL-1, and IL-6 perpetuate the inflammation and activate osteoclasts (cells that degrade bone), causing the characteristic joint erosions.

Citrullination of proteins — a post-translational modification that occurs in inflamed tissues — is a key event in RA. Citrullinated proteins become "foreign" to the immune system, triggering anti-CCP production and perpetuating the autoimmune cycle.

Symptoms

RA symptoms usually develop gradually over weeks to months. An insidious, symmetric onset in the small joints is the classic presentation, though atypical forms exist.

Joints Typically Affected

Diagnosis

Early diagnosis of RA is decisive. The 2010 ACR/EULAR classification criteria were designed to enable diagnosis in the early stages, before bone erosions develop.

Laboratory Tests

Rheumatoid Arthritis vs. Osteoarthritis

Distinguishing RA from osteoarthritis (OA) is critical because their treatments differ radically. RA is an inflammatory autoimmune disease; OA is degenerative. The key differences: RA affects symmetric hand joints (metacarpophalangeal and proximal interphalangeal), whereas OA prefers weight-bearing joints (knees, hips) and the distal interphalangeal joints. Morning stiffness in RA is prolonged (> 60 minutes); in OA it lasts less than 30 minutes.

On lab testing, RF and Anti-CCP are typically positive in RA (especially Anti-CCP, with 95-98% specificity) and negative in OA. ESR and CRP are elevated in active RA and normal in pure OA. On imaging, OA shows osteophytes and subchondral sclerosis, whereas early RA may show only periarticular osteopenia, progressing to erosions in the small hand joints.

Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) can cause arthritis that mimics RA, with symmetric involvement of the small hand joints. The key difference is that lupus arthritis is usually non-erosive (it doesn't destroy joints) and systemic signs are more prominent: skin rashes (butterfly malar erythema), photosensitivity, and renal, pleural, and neurologic involvement.

The antinuclear antibody (ANA) is positive in >95% of SLE cases but can also turn positive at low titers in RA. Anti-double-stranded DNA is the most specific antibody for SLE. When the clinical picture overlaps, the rheumatologist must weigh the full set of classification criteria to tell the two conditions apart.

Psoriatic Arthritis

Psoriatic arthritis (PsA) can mimic RA, especially in its symmetric polyarticular form. The most important diagnostic clue is skin or nail psoriasis — actively examine the scalp, navel, gluteal cleft, and nails (onycholysis, nail pitting). PsA favors the distal interphalangeal (DIP) joints, which RA rarely affects.

RF and Anti-CCP are usually negative in PsA. HLA-B27 may be positive, especially in axial forms. Enthesitis (inflammation at tendon insertions) and dactylitis ("sausage" finger from arthritis and tenosynovitis) are hallmarks of PsA and rarely occur in RA.

Treatments

Over the past two decades, the "treat-to-target" strategy has revolutionized RA treatment, aiming for clinical remission or at least low disease activity. Disease-modifying anti-rheumatic drugs (DMARDs) are the foundation.

Conventional DMARDs

Methotrexate (MTX) is the anchor medication in RA treatment. It acts as an immunomodulator, inhibiting purine synthesis and reducing immune cell proliferation. The usual dose is 15-25 mg per week (oral or subcutaneous), and its full effects can take 6-12 weeks to manifest.

Other conventional DMARDs include leflunomide, sulfasalazine, and hydroxychloroquine. These can be combined with methotrexate to boost efficacy.

Acupuncture as Complementary Treatment

In RA, acupuncture is used exclusively as a complementary therapy, never as a substitute for DMARDs. Its role is to assist in pain control, reduce the need for analgesics, and improve quality of life.

Experimental studies suggest acupuncture may modulate the immune response in RA contexts — with signals of effect on pro-inflammatory cytokines (TNF-alpha, IL-6), anti-inflammatory cytokines (IL-10), and the hypothalamic-pituitary-adrenal axis. The findings remain heterogeneous and don't, on their own, translate into impact on disease progression.

Acupuncture can serve as an adjunct for managing RA-related fatigue, a symptom that often persists even when inflammatory activity is controlled. Neuroimaging studies suggest that brain circuits tied to chronic fatigue may be involved, but the clinical evidence is still preliminary.

Prognosis

RA prognosis has improved dramatically with modern treatments. Patients diagnosed and treated early with DMARDs do remarkably well, with many reaching remission or low disease activity. The "treat-to-target" concept has revolutionized outcomes.

Myths and Facts

When to Seek Medical Care