Reactive arthritis commonly presents as florid inflammation of
one or two of the large weight-bearing joints. Asymmetric involvement
of small and large joints with dactylitis, as well as enthesitis,
tenosynovitis, and bursitis, may also occur. The joints may be very
hot, red, tender, and painful, and laboratory investigation may show
markedly elevated inflammatory indices. A history in the patient
of recent infection, infectious contact, or travel should alert
to the possibility of reactive arthritis. In the case of monarthritis,
the possibility of septic arthritis may necessitate treatment with
intravenous antibiotics while awaiting the results of arthrocentesis
and joint fluid culture. In the presence of relatively normal “inflammatory” blood
tests, several other acutely presenting conditions may have to be
excluded. Acute orthopedic conditions of the hips such as slipped
capital femoral epiphysis or Legge-Calve-Perthes should be distinguishable
radiographically. Reflex sympathetic dystrophy (RSD) may present
with an acutely painful, swollen joint, and this may be difficult
to distinguish from reactive arthritis in spite of the presence
of the characteristic “la belle indifference.” A
nuclear bone scan may be diagnostically helpful, with inflammatory
processes demonstrating increased perfusion, but RSD characterized
by decreased blood flow in the involved area. Support for the diagnosis
of reactive arthritis is also provided by intestinal, urethral,
and conjunctival cultures revealing one of the organisms known to
incite reactive arthritis. However, although suggestive, this is
no more definitive in proving the existence of reactive arthritis
than does the absence of organisms exclude the possibility. Fortunately,
reactive arthritis is most often transient, lasting only days to weeks,
so a diagnosis may be assumed in retrospect, following a severe,
self-limited arthritis. In some cases the arthritis may persist
for months, sometimes with remissions and exacerbations, and in
1% to 3% of cases, patients (especially those
with positive HLA-B27) develop chronic synovitis following an arthritogenic
infection.