Rheumatoid Arthritis

TL;DR. Rheumatoid arthritis is the immune system attacking the lining of your joints. That lining, normally a slippery membrane a few cells thick, becomes an inflamed, thickened, invasive tissue that eats into cartilage and bone. Untreated, it destroys joints permanently within a few years, and it is not confined to joints: it inflames lungs, eyes, blood vessels, and arteries, and it shortens life mostly through heart disease. What makes this chapter different from most in this book is that the treatment changed completely within one professional lifetime. A rheumatologist trained in 1985 expected to watch patients become deformed and disabled. One trained today expects to achieve remission, and the difference is not one drug but a strategy: treat immediately, aim at a target, and measure whether you hit it.

Key takeaways

• About 18 million people live with rheumatoid arthritis, roughly 0.5 to 1 percent of adults, and about three-quarters are women.
• The clock matters more than the drug. Treating within the first 12 weeks produces substantially better outcomes than treating at 12 months, which is called the window of opportunity.
• Smoking is the strongest environmental cause, and it works through a specific chemical mechanism that also explains why gum disease is implicated.
• Anti-CCP antibodies appear years before symptoms, which makes rheumatoid arthritis one of the few autoimmune diseases where prevention trials are now possible.
• It is a cardiovascular disease as well as a joint disease. Chronic inflammation roughly increases heart attack and stroke risk by half, and controlling the inflammation reduces it.
• Remission is now a realistic goal for a substantial proportion of patients, and the erosive deformities that defined the disease a generation ago have become uncommon where treatment starts early.

What it is

In short: A chronic, symmetrical, inflammatory arthritis of the joint lining that erodes cartilage and bone, and that also affects organs far from any joint.

Rheumatoid arthritis (RA) is a chronic autoimmune disease in which the immune system attacks the synovium, the membrane lining joints and tendon sheaths.

It is diagnosed clinically, supported by blood tests and imaging. The 2010 classification criteria score four things: how many and which joints are involved (small joints count for more), whether rheumatoid factor or anti-CCP antibodies are present and at what level, whether inflammatory markers (CRP or ESR) are raised, and whether symptoms have lasted six weeks or more.

The pattern is the diagnosis. What distinguishes rheumatoid arthritis at the bedside:

Don't be confused: "arthritis" is not one disease, and the two commonest kinds are opposites. Osteoarthritis is a mechanical and metabolic failure of cartilage repair, worse with use, treated with exercise and analgesia. Rheumatoid arthritis is an autoimmune inflammatory disease, better with use and worse with rest, and it needs drugs that suppress the immune system within weeks to prevent permanent damage. Getting the two confused delays the one where delay causes irreversible harm. The practical rule: prolonged morning stiffness plus symmetrical swelling of the small joints is a rheumatology referral, not a painkiller.

The history

In short: A disease possibly unknown in Europe before 1800, described in 1800, named in 1859, and transformed by methotrexate in the 1980s and biologics in 1998.

Rheumatoid arthritis has an odd historical record. Convincing skeletal evidence of it in the Old World before about 1800 is scarce, while erosive arthritis consistent with RA has been found in Native American skeletal remains from several thousand years ago in the Tennessee and Ohio river valleys. This has led to a genuine and unresolved argument about whether the disease is ancient and simply unrecorded, or whether something changed, possibly an environmental trigger arriving in Europe after contact with the Americas.

The strategy change may have mattered as much as the drugs. Trials comparing "treat until the target is reached, measuring formally" against "treat and see how the patient seems" found the first approach substantially better using the same medicines.

What actually goes wrong

In short: Genes plus smoking plus a chemical modification of your own proteins produces antibodies against them, and the resulting inflamed joint lining physically eats bone.

The synovium becomes something else

A normal synovium is a delicate membrane one to three cells thick that produces the fluid lubricating a joint. In rheumatoid arthritis it becomes:

1. Infiltrated by T cells, B cells, macrophages, and plasma cells, sometimes organising into structures resembling lymph nodes inside the joint.
2. Thickened, proliferating into a mass called a pannus, from the Latin for cloth.
3. Invasive. The pannus creeps over cartilage and physically digests it, using enzymes (matrix metalloproteinases) released by the synovial cells.
4. Bone-destroying. Inflammatory signals, especially TNF-alpha, IL-6, and RANKL, activate osteoclasts (Chapter 7), the cells that dissolve bone. This produces the characteristic erosions at the joint margins that are visible on X-ray and, earlier, on ultrasound and MRI.

This is why the damage is permanent. Cartilage has no blood supply and almost no capacity to repair (Chapter 3). Eroded bone does not regrow into its original shape. Every month of uncontrolled inflammation costs joint structure that no later treatment restores, which is the entire argument for speed.

Where the autoimmunity comes from

The best-understood chain in autoimmune disease, and worth following because it explains the smoking link:

1. Genetic susceptibility. Certain HLA-DRB1 variants, collectively called the shared epitope, are strongly associated. They encode a groove that binds a particular kind of modified peptide especially well. Add PTPN22 and around a hundred other loci. Heritability is roughly 50 to 60 percent.
2. Citrullination. An enzyme (peptidyl arginine deiminase) converts the amino acid arginine in your own proteins into citrulline. This is a normal process that increases with inflammation, cell death, and stress.
3. Smoking accelerates it. Cigarette smoke increases citrullination in the lung. So does infection with Porphyromonas gingivalis, a gum disease bacterium that uniquely possesses its own citrullinating enzyme, which is the mechanistic basis for the periodontitis association (Chapter 62).
4. The immune system attacks the modified proteins. In people carrying the shared epitope, citrullinated peptides fit the HLA groove and are presented to T cells, which help B cells produce anti-citrullinated protein antibodies (ACPA), measured clinically as anti-CCP antibodies.
5. The attack localises to joints, for reasons still not fully explained, possibly because citrullinated proteins are present in synovium and because immune complexes deposit there.
6. A self-sustaining inflammatory loop establishes itself, with TNF-alpha and IL-6 at its centre. This is why blocking either one works.

Antibodies come first, by years. Anti-CCP antibodies are detectable in stored blood samples 5 to 10 years before symptoms in a large proportion of patients. There is a genuine pre-clinical phase, and that fact is the basis of current prevention trials in antibody-positive people who do not yet have arthritis.

Two diseases wearing one name

Seronegative disease is a more heterogeneous group, and a proportion are eventually reclassified as psoriatic arthritis or another spondyloarthritis (Chapter 52).

What it does to the body

In short: Joints first and most visibly, then lungs, eyes, blood vessels, and arteries, and the arteries are what shortens life.

The joints

Early: pain, swelling, and prolonged morning stiffness in the small joints of hands and feet, symmetrically. Grip weakens. Fine tasks become difficult.

Later, if uncontrolled, the classic deformities, which are worth naming because they are now becoming historical:

Seeing these in a patient under 60 today is a marker of undertreatment or of very long-standing disease, and their disappearance is one of the clearest visible results of modern rheumatology.

Beyond the joints

Roughly 40 percent of patients develop at least one extra-articular manifestation.

Fatigue deserves emphasis because it is systematically under-addressed. Surveys of patients consistently place it at or near the top of what they want treated, while clinical assessment focuses on swollen joint counts and inflammatory markers, which it tracks only loosely.

Is it deadly?

In short: It shortens life by a few years, mostly through cardiovascular disease and infection, and the gap has narrowed substantially with better control of inflammation.

• Historically, rheumatoid arthritis reduced life expectancy by roughly 3 to 10 years.
• The excess is driven mainly by cardiovascular disease, then infection (from both the disease and its treatment), then lung disease and lymphoma.
• The cardiovascular risk is comparable in magnitude to type 2 diabetes, which is why guidelines recommend formal cardiovascular risk assessment in all patients, typically with a multiplier applied to standard risk calculators.
• Better disease control narrows the gap. Cohort studies since the introduction of treat-to-target strategies and biologics show declining mortality, and patients achieving sustained remission approach general-population survival.

The mechanism connecting the two is the thread running through this book: chronic systemic inflammation damages the artery lining, accelerating atherosclerosis (Chapter 21). Treating the inflammation treats both diseases.

Is it contagious?

In short: No. It cannot be transmitted, and the infections associated with it are triggers of an immune response, not the disease itself.

Rheumatoid arthritis is not contagious. You cannot catch it from someone, and living with, caring for, or being related to a patient carries no transmission risk.

Two genuine connections cause confusion:

Bacteria contribute to causation without being transmissible as the disease. The gum bacterium P. gingivalis is implicated through citrullination, and the lung microbiome has been suggested as a contributor. Catching gum disease is possible; catching rheumatoid arthritis is not, and the overwhelming majority of people with periodontitis never develop it.

Family clustering is genetic. A first-degree relative of someone with RA has roughly a three to five fold increased risk, from shared genes rather than shared exposure. Identical twin concordance is around 15 to 30 percent, which is well above the population rate and well below 100, which is exactly what a disease requiring both genes and environment looks like.

Who gets it

In short: Three-quarters women, peak onset 30 to 50, and smoking is the dominant modifiable cause.

Geographically, prevalence is around 0.5 to 1 percent in most populations studied, with notably high rates reported in some Indigenous North American populations and lower rates in parts of rural Africa and Asia, though case-finding differences complicate the comparison.

Treatment, and how it works

In short: Start disease-modifying treatment within weeks, aim explicitly at remission, measure whether you got there, and escalate if not.

The strategy, which matters as much as the drugs

Three principles define modern practice:

1. The window of opportunity. Starting a disease-modifying drug within the first 12 weeks of symptoms produces better remission rates, less radiographic damage, and more drug-free remission than starting later. This is why "early arthritis clinics" with rapid referral pathways exist.
2. Treat to target. Choose an explicit target (remission, or low disease activity if remission is not achievable), measure it formally with a composite score such as DAS28, and escalate treatment every one to three months until the target is reached. The landmark TICORA trial found that intensive, formally measured management produced dramatically better outcomes than routine care using the same medicines.
3. Steroids as a bridge, not a home. Corticosteroids work within days, which is invaluable while a slow-acting drug takes effect, and their long-term harms are severe (Chapter 49). Modern practice uses them briefly and tapers.

The drugs

Conventional synthetic DMARDs (disease-modifying antirheumatic drugs):

Biologic DMARDs, given by injection or infusion, each blocking one specific signal:

Targeted synthetic DMARDs (JAK inhibitors): tofacitinib, baricitinib, upadacitinib, filgotinib. Small molecules, taken as tablets, blocking the intracellular signalling pathway that many cytokines share. Rapidly effective, and carrying a specific safety concern discussed below.

Biosimilars, near-identical copies of biologics whose patents have expired, have reduced prices substantially and widened access, which is one of the more consequential quiet developments in the field.

Non-drug treatment

Not optional, and consistently under-provided:

• Exercise. Both aerobic and resistance training improve function, fatigue, and cardiovascular risk, and do not damage joints when disease is controlled. The old advice to rest inflamed joints indefinitely caused muscle wasting and deconditioning.
• Physiotherapy and occupational therapy: joint protection techniques, splints, aids, and workplace adaptation.
• Smoking cessation, which improves both disease activity and drug response as well as reducing cardiovascular risk.
• Cardiovascular risk management: statins, blood pressure control, and treating the inflammation itself.
• Vaccination, arranged before immunosuppression starts where possible.
• Foot care and appropriate footwear, since forefoot involvement is common and under-treated.

What treatment costs

In short: Infection is the shared price, methotrexate is dosed weekly and the daily-dosing error has killed people, and JAK inhibitors carry a specific cardiovascular signal in older patients.

Don't be confused: methotrexate for rheumatoid arthritis is a WEEKLY dose, and taking it daily is lethal. Accidental daily dosing has caused deaths from marrow failure and mucosal destruction. Prescriptions carry specific warnings, dispensing is often restricted to one strength of tablet to prevent confusion, and it remains one of the most cited medication safety errors in the world. If you take methotrexate, know which day is your day, and check any new prescription against that.

What the person can do

In short: Get seen fast, take the anchor drug properly, keep moving, stop smoking, and treat your heart as part of your arthritis.

• Get referred urgently if you suspect it. Prolonged morning stiffness with symmetrical swelling of small joints, especially with a positive squeeze test across the knuckles, warrants rheumatology referral, not months of anti-inflammatories. Ask directly for referral if it is not offered.
• Start treatment even if you feel it is "not that bad yet." The damage accumulates during the period when symptoms are tolerable.
• Take methotrexate on the same day each week, with the folic acid as prescribed, and never daily.
• Attend the blood monitoring. It is the mechanism by which serious toxicity is caught before it causes harm, and missing it is the commonest reason treatment is interrupted.
• Stop smoking. It causes the disease, worsens it, and reduces response to treatment.
• Exercise, including resistance training. Joints controlled by treatment are not damaged by use, and muscle protects joints.
• Get vaccinated before starting immunosuppression where possible: influenza, pneumococcal, COVID-19, shingles (the non-live recombinant vaccine), and hepatitis B where indicated. Live vaccines generally cannot be given during treatment.
• Have your cardiovascular risk assessed, and treat it. This is the single most under-addressed part of rheumatoid care.
• Report a sore throat, fever, or feeling unwell promptly while on immunosuppression, and know which drugs to pause during infection.
• Plan pregnancy in advance. Several drugs must be stopped and replaced with pregnancy-safe alternatives, and uncontrolled disease is itself bad for pregnancy, so the answer is planning rather than stopping everything on discovering you are pregnant.
• Tell your dentist and any anaesthetist about the diagnosis, the drugs, and any neck symptoms.

Living with it

In short: A fluctuating, invisible, fatiguing disease in people who mostly look well, and the fatigue and unpredictability cause more life disruption than the joint counts suggest.

Rheumatoid arthritis typically begins between 30 and 50, which collides directly with careers, young children, and financial commitments. Work disability rates were historically high, and have improved substantially with early treatment, though a significant proportion still reduce hours or leave work.

Three features shape daily life more than the clinical measures do:

Fatigue, which patients rank near the top of their priorities and which responds only partly to controlling inflammation. Exercise, sleep, and psychological approaches help; nothing abolishes it.

Unpredictability. Flares arrive without warning, which makes commitments hard and is poorly understood by employers and family who see someone who looks well.

Invisibility. Early inflammatory disease produces little that anyone else can see, and the deformities that once made the disease visible are now largely prevented, which is an unambiguous good with a small social cost: the illness is harder for others to credit.

Depression and anxiety are around twice as common as in the general population, are under-diagnosed, and independently worsen pain and function (Chapter 42).

What's next

In short: Preventing the disease in antibody-positive people before it starts, and predicting which drug will work for which patient.

• Prevention. Because anti-CCP antibodies appear years before symptoms, trials have tested whether treating antibody-positive people with arthralgia can prevent progression to arthritis. Results so far are mixed and genuinely interesting: some agents delayed onset during treatment without clearly preventing disease afterwards. This is the most conceptually important work in the field.
• Precision treatment. At present, choosing between a dozen effective biologics is largely trial and error, with roughly 30 percent of patients failing each successive agent. Synovial biopsy studies and molecular profiling are attempting to predict who responds to what, and the R4RA trial showed that synovial B-cell status predicted response to rituximab versus tocilizumab.
• Drug-free remission. A minority of patients who achieve sustained remission can taper and stop treatment. Identifying them in advance rather than by trial and error is an active question.
• Better fatigue treatment, which remains the largest gap between what is measured and what patients want.
• Access. Biosimilars have cut costs substantially, and biologic therapy remains unavailable to most rheumatoid arthritis patients worldwide, which is the same equity problem that runs through this book.

Sources and notes

Global prevalence of approximately 18 million: WHO and Global Burden of Disease 2019 estimates. 2010 ACR/EULAR classification criteria: Aletaha et al., Arthritis & Rheumatism, 2010. Shared epitope hypothesis: Gregersen, Silver, and Winchester, 1987. Citrullination, smoking, and the gene-environment interaction: Klareskog et al., Arthritis & Rheumatism, 2006. P. gingivalis peptidylarginine deiminase: Wegner et al., Arthritis & Rheumatism, 2010. Anti-CCP antibodies preceding symptoms: Rantapää-Dahlqvist et al., Arthritis & Rheumatism, 2003; Nielen et al., 2004. Window of opportunity: van der Linden et al., Arthritis & Rheumatism, 2010. Treat-to-target and TICORA: Grigor et al., The Lancet, 2004. Anti-TNF development: Feldmann and Maini, from 1992. Cardiovascular risk magnitude: Avina-Zubieta et al., meta-analyses. Mortality gap and its narrowing: Norwegian, Swedish, and US cohort analyses. JAK inhibitor safety: ORAL Surveillance, Ytterberg et al., NEJM, 2022. Synovial phenotype-guided therapy: Humby et al., The Lancet, 2021 (R4RA). Paleopathological argument about New World origin: Rothschild and colleagues; the question remains open.

Open questions. Whether rheumatoid arthritis can be prevented in antibody-positive individuals is unresolved and under active trial. Why the immune attack localises to joints when the citrullination trigger occurs in the lung is not explained. The New World origin hypothesis is genuinely contested. No treatment reliably addresses fatigue.

Next: the disease that can affect almost any organ, and the family of conditions around it. 👉