Diagnosis

Reactive arthritis

Etiology

Cause [dir][uic]

• GI infections: Salmonella enteritidis, Shigella flexneri, and S. disenteriae, Yersinia enterocolitica, Campylobacter jejuni, Clostridium difficile

• Genitourinary infections: Chlamydia trachomatis, Neisseria gonorrhea, Mycoplasma hominis, and Ureaplasma urealyticum

Pathophysiology [uic]

1. Molecular mimicry hypothesis suggests that a similarity exists at the molecular level between the HLA-B27 molecule and the inciting organisms

2. Activated cytotoxic-T cells attack the synovium and other self-antigens

3. The classic triad of Reiter syndrom:

   • Arthritis

   • Urethritis

   • Conjunctivitis

4. Clinical manifestation: [dir][uic]

   • Joint distribution: Knee (60%), talocrural joint (55%), metatarsophalangeal joint (45%), radiocarpal joint (45%)

   • Eye: Conjunctivitis, anterior uveitis episcleritis, and keratitis

   • Genitourinary: urethritis, cervicitis, prostatitis, salpingo-oophoritis, cystitis or circinate balanitis)

   • Mucosal and skin: Mucosal ulcers, geographic tongue, keratoderma blennorrhagica, erythema nodosum, hyperkeratotic skin and erythematous dermatitis

   • Cardiac: Carditis, aortic, conduction and valvular abnormalities

   • Nail changes: Onycholysis, subungual keratosis, or nail pits

Risk factors [dir]

• Age 18-40

• Presence of HLA-B27 (Scandinavian countries)

• Endemic pathogens

Epidemiology

Incidence per 100.000 [rfw][dir][8w7][miu][khc][p6c][3kp]

Approach

• Blood test: erythrocyte sedimentation rate (ESR), CRP, RF, ANA [edz]

• NAAT positive for chlamydia

  • Urine / Urethra

  • Cervix

  • Synovial fluid

• Urine stix

• Urine culture

• Chlamydia-serology/PCR in joint

• X-ray

• MRI

• CT

• Ultrasound

• Scintigraphy

• Arthrocentesis

Diagnostic criteria [dir]

1. Major criteria:

   • Arthritis, meeting 2 of the following 3 characteristics:

     • Asymmetric

     • Mono- or oligoarthritis

     • Lower limb involvement

   • Preceding symptomatic infection, meeting one of the following characteristics:

     • Enteritis (diarrhea occurring 3 days to 6 weeks before the onset of arthritis)

     • Urethritis (dysuria/discharge occurring 3 days to 6 weeks before the onset of arthritis)

2. Major criteria:

   • Presence of a triggering infection: urine culture, urethral swab, or stool culture

   • Presence of persistent synovial infection: positive immunohistology or PCR

Treatment

1. NSAIDs [dir][3kp][rfw][wr2][edz]

2. Intra-articular glucocorticoid therapy

3. Antibiotics if an infectious agent has been identified as a trigger [uic]

   • Combination of doxycycline + rifampin or azithromycin + rifampin for 6 months

4. Chronic Reactive Arthritis:

   • Disease-Modifying Antirheumatic Drugs

     • Sulfasalazine

     • Methotrexate

   • Biological Agents

     • TNF-α Antibody

     • Interleukin-6 Receptor Antibody

     • Interleukin-17a Monoclonal Antibody

Differential diagnoses

Acute exanthematic pustulosis, Acute lymphoblastic leukemia, Ankylosing spondylitis, Balanitis, Behcet's disease, Celiac disease, Conjunctivitis, Crohn disease, Cutaneous T-cell lymphoma, Eczema, Erythema nodosum, Gastroenteritis, Glaucoma, Gonorrhea, Gout, HIV, Kawasaki disease, Lyme disease, Parvovirus B19, Psoriasis, Psoriatic arthritis, Rheumatic fever, Rheumatoid arthritis, Sarcoidosis, Scabies, Scleritis, Septic arthritis, Still disease, Syphilis, Systemic lupus erythematosus, Tendonitis, Tenosynovitis, Tuberculosis, Ulcerative colitis, Uveitis, Viral hepatitis, Whipple's disease