Reactive arthritis

Reactive arthritis, formerly known as Reiter syndrome, is a post-infectious inflammatory arthritis. It is a seronegative spondyloarthropathy that occurs following a recent infection.

It has associations with HLA-B27 as well as sexually transmitted infections and gastrointestinal infections.

Pathophysiology

Reactive arthritis is triggered by bacterial infecitions (predominantly Chlamydia trachomatis or enterobacteria). In these patients we find bacterial DNA within the joint. The bacteria itself may still be alive or the degradation products are seen. These bacteria or bacterial products trigger an immune response leading to the symptoms present. It is important to not that although these bacteria/bacterial products are found in the joint, there is no infection in the joint as this is what is seen in septic arthritis.

HLA-B27 is found in 30-50% of cases and is associated with spondyloarthropathies. However, its role in the disease process for reactive arthritis is not well understood.

💡 A triggering infection is seen in about 50% of cases, although the infection may occur up to a month prior to the development of reactive arthritis.

⚠️ Risk factors

• Male sex (male to female ratio of 1.5:1)
• Age - early adulthood, commonly presents between the age of 20 and 40
• HLA-B27
• HIV
• Sexually transmitted infections - commonly Chlamydia.
• Gastrointestinal infections - commonly Shigella, Yersinia, Campylobacter, Salmonella.

😷 Presentation

It usually presents 1-4 weeks after an infection.

• Arthritis - the arthritis is typically oligoarthritis that is asymmetrical. It may often present as a monoarthritis (in the knee especially).
• Axial arthritis - especially in the SI joints and lumbosacral spine. It will lead to lower back pain that is worse at night and in the morning.
• Dactylitis
• Enthesitis - commonly in the Achilles tendon or plantar fascia.
• Fever and lethargy

Other, less common, associations with the disease are:

• Conjunctivitis or anterior uveitis
• Urethritis
• Keratoderma blenorrhagica - dark maculopapular rash on the palms and soles
• Aphthous oral ulcers
• Circinate balanitis - painless ulcers and plaque-like lesions on the shaft or glans of the penis
• Cardiac involvement - aortitis (which may lead to aortic regurgitation or cardiac failure) or arrhythmias.

💡

The classic triad of reactive arthritis

1. Arthritis
2. Conjunctivitis
3. Urethritis

🔍 Investigations

⭐️ It is a clinical diagnosis. However, we need to exclude serious pathology such as septic arthritis.

• ⭐️ Joint aspiration with synovial fluid analysis - to rule out septic arthritis and crystalarthropathies (gout and pseudogout)
• Although there is evidence of microbial antigens in the synovium, organisms cannot be cultured from joint fluid.
• Bloods
• CRP/ESR - raised
• ANA - to rule out other forms of arthritis. It will be negative.
• RF - to rule out other forms of arthritis. It also will be negative.
• HIV antibodies - as reactive arthritis is more common in this demographic. So, we need to exclude HIV if not already diagnosed with it
• NAAT - in asymptomatic men and women with suspected sexually acquired reactive arthritis.

🧰 Management

💡 Most cases of reactive arthritis self-resolve within 6 months and do not recur.

🚨 Complications

• Secondary osteoarthritis - due to inflammation → cartilage damage → bony erosion.
• Uveitis