Reactive arthritis

Overview

Reactive arthritis is a type of inflammatory arthritis that develops in response to an infection in another part of the body, most commonly the gastrointestinal or genitourinary tract. It is characterized by joint pain and swelling, often accompanied by inflammation of the eyes and urinary tract. Formerly known as Reiter’s syndrome, reactive arthritis is now considered a broader category of autoimmune conditions triggered by infections.

This syndrome typically affects young adults, especially males between the ages of 20 and 40. While the initial infection may resolve, the immune system’s abnormal response to that infection can lead to prolonged inflammation in the joints and other tissues. The condition can be self-limiting, but in some individuals, it becomes chronic or recurrent.

Causes

Reactive arthritis is caused by an abnormal immune response to a preceding infection, typically occurring within 1 to 4 weeks before the onset of arthritis. The most common infections that trigger reactive arthritis include:

Genitourinary Infections:

• Chlamydia trachomatis – a sexually transmitted bacterial infection

Gastrointestinal Infections:

• Salmonella

• Shigella

• Yersinia

• Campylobacter

• Clostridioides difficile (less common)

Risk Factors:

• HLA-B27 gene: A genetic marker associated with a higher risk and more severe disease

• Sex: Males are more commonly affected when the trigger is a sexually transmitted infection

• Age: Most common in adults aged 20–40

• Immunogenetic susceptibility: Autoimmune predisposition plays a role

Symptoms

Reactive arthritis commonly presents with a classic triad of:

1. Arthritis (joint inflammation)

2. Urethritis (inflammation of the urinary tract)

3. Conjunctivitis (inflammation of the eyes)

However, not all patients develop all three symptoms. Other manifestations may occur depending on the severity and organ systems involved.

Musculoskeletal Symptoms:

• Painful, swollen joints – typically in the knees, ankles, and feet

• Asymmetric oligoarthritis – affecting a few joints on one side of the body

• Enthesitis – inflammation where tendons attach to bone (e.g., Achilles tendon)

• Dactylitis – "sausage digits" (swollen fingers or toes)

• Low back pain or sacroiliitis in some cases

Genitourinary Symptoms:

• Painful urination (dysuria)

• Urethral discharge

• Prostatitis in men or cervicitis in women

Ocular Symptoms:

• Conjunctivitis (red, itchy eyes)

• Uveitis (inflammation of the middle layer of the eye)

Other Features:

• Skin lesions such as keratoderma blennorrhagicum (scaly rash on soles or palms)

• Painless oral ulcers

• Nail changes similar to psoriasis

Diagnosis

There is no specific test for reactive arthritis. Diagnosis is made based on clinical history, physical examination, and exclusion of other causes of arthritis. Key steps include:

History and Physical Examination:

• Recent history of diarrhea or sexually transmitted infection

• Joint pattern and timing of symptom onset

Laboratory Tests:

• Inflammatory markers: Elevated ESR and CRP

• HLA-B27 testing: Positive in 50–80% of cases, especially with axial involvement

• Urethral/cervical swabs or urine PCR: For Chlamydia trachomatis

• Stool cultures: If gastrointestinal infection is suspected

• Rheumatoid factor and ANA: Negative, helping rule out other rheumatologic diseases

Imaging:

• X-rays: May show soft tissue swelling or joint erosion in chronic cases

• MRI: Helpful in detecting early sacroiliitis or enthesitis

Treatment

The management of reactive arthritis focuses on symptom relief, controlling inflammation, treating the underlying infection, and preventing long-term joint damage.

1. Antibiotic Therapy:

• Indicated if Chlamydia or other bacterial infections are present

• Doxycycline or azithromycin for Chlamydia trachomatis

• Antibiotics are not useful once arthritis is established, except to eradicate persistent infections

2. Anti-inflammatory Medications:

• NSAIDs: First-line for joint pain and swelling (e.g., ibuprofen, naproxen)

• Corticosteroids: Oral or intra-articular for severe inflammation unresponsive to NSAIDs

3. Disease-Modifying Anti-Rheumatic Drugs (DMARDs):

• Used in chronic or refractory cases

• Methotrexate or sulfasalazine may be prescribed for persistent arthritis

4. Biologic Therapy:

• TNF inhibitors may be considered in severe, treatment-resistant cases

5. Supportive Care:

• Physical therapy to maintain joint function and muscle strength

• Occupational therapy for daily activity support

Prognosis

Reactive arthritis is often self-limited, with most cases resolving within 3 to 6 months. However, about 15–30% of individuals may develop chronic arthritis or recurrent episodes. Prognosis depends on the presence of risk factors such as HLA-B27 positivity, severity of initial symptoms, and whether the arthritis persists beyond 6 months.

With early intervention and appropriate treatment, most individuals experience full recovery. Long-term outcomes are generally favorable, though some patients may require ongoing management for joint symptoms or complications such as uveitis or chronic enthesitis.

Prevention strategies include early treatment of infections, safe sexual practices, and close monitoring of patients with known risk factors for autoimmune joint involvement.