Reactive Arthritis is an acute inflammatory arthritis occurring with, or following, an intercurrent infection, but without evidence of the causative organism in the joint. Reactive arthritis can occur at any age and typically follows 7-10 days after gastroenteritis (young children), involving lower limb large joints (knee>ankle>hip). Infections are usually due to Shigella, Salmonella, Yersinia, Campylobacter organisms. Acute phase reactants are usually very high, blood cultures and autoantibodies are negative. The diagnosis may rest on serology or stool cultures or be one of exclusion of infection. There is an association with HLA-B27 antigen being positive and a chronic course.
In adolescents, it is important to consider sexually acquired Gonococcal arthritis or Chlamydia infection. Patients may have multiple infections: (Chlamydia, Gonococcus and HIV). Safeguarding concerns may be warranted. Red eyes due to conjunctivitis may also be present: Reiter's disease or syndrome describes the triad of urethritis, conjunctivitis and arthritis.
NSAIDS and intra-articular steroid injections are often helpful with persistent arthritis (defined as >4-6 weeks) and after septic arthritis has been excluded.
Poncet's disease - a reactive polyarthritis after mycobacterial infection (TB).
Gonococcal Arthritis - may present with fever, rigors, skin lesions (macular rash, pustules, or blisters), tenosynovitis, and polyarthritis. The sexual history needs to be explored but the possibility of sexual abuse should be considered. The knee is most commonly affected, but any joint may be involved. If suspected, Gram stain, and cultures of synovial fluid, blood cultures are done but can be falsely negative. Coexistent sexually acquired infections need to be considered.
Acute Rheumatic Fever - ARF is an auto-immune reaction which follows Group A streptococcus infection with multisystem involvement of heart, joints, brain and skin. Arthritis tends to occur early and is often migratory (sometimes called 'migratory' or 'flitting' as it moves from joint to joint), tends to affect large joints (often legs first). Rheumatic heart disease is a serious complication with high morbidity and mortality. Treatment of ARF is with prolonged antibiotics and management of organ involvement such as heart failure from carditis or valvular disease. Neurological complications include chorea (erratic limb movements from extrapyramidal involvement).