Reactive arthritis and post-infectious inflammatory syndromes: Case

Problem representation

This is a nine-year-old boy with the asymmetric lower-limb oligoarthritis, the enthesitis at the Achilles tendon and the dactylitis, erupting three weeks after the Campylobacter gastroenteritis, with the sterile joint aspirate and the positive HLA-B27. The problem representation is the post-enteric reactive arthritis on the spondyloarthritis spectrum, and the three-week latency after the gastrointestinal infection is the anchor. [4]

The sepsis exclusion

The first step is the sepsis exclusion. The child is afebrile and well, the joint aspirate shows the white cell count of twelve thousand per microlitre with the negative gram stain and culture, and the picture is consistent with the sterile inflammatory arthritis rather than the septic arthritis. The septic joint yields the pus with the white cell count above fifty thousand per microlitre and the positive culture, and this child's aspirate excludes it. [9]

The mechanism

The Campylobacter triggered the arthritis through the molecular mimicry. The HLA-B27 molecule presented the bacterial peptide to the CD8-positive T cell, the T cell cross-reacted with the self synovial antigens, and the interleukin-23 and interleukin-17 axis sustained the sterile synovitis. The joint is inflamed but sterile, and the bacterial antigens persist in the synovial macrophages. [5]

The differential from the streptococcal syndromes

The post-streptococcal reactive arthritis is excluded by the enteric trigger, the three-week latency that is longer than the ten-day window of the streptococcal syndrome, and the normal streptococcal serology. The acute rheumatic fever is excluded by the same features, and the absence of the carditis, the chorea and the migratory polyarthritis. The antistreptolysin-O and the anti-DNase B are sent to confirm the exclusion, and the echocardiogram is reserved for the atypical case or the positive streptococcal serology. [3][1]

The stepwise management

The first-line is the non-steroidal anti-inflammatory drugs, given regularly. The naproxen is given at ten milligrams per kilogram per day in two divided doses, and the full anti-inflammatory dose is continued for the duration of the active arthritis. The child is reviewed at the two-to-four-week interval, and the intra-articular triamcinolone hexacetonide is injected for the persistent monoarthritis that does not respond to the non-steroidal anti-inflammatory drug. The disease-modifying drugs and the biologics are reserved for the persistent disease beyond the three to six months. [9]

The safety-net and the prognosis

The family is told that the majority of the reactive arthritis resolves within the three to six months, and the self-limiting course is the expected outcome. The slit-lamp is organised for the uveitis because the HLA-B27 is positive and the uveitis is silent until it scars the sight, and the family is told to return immediately for the red eye, the pain or the photophobia. The paediatric rheumatology referral is arranged for the ongoing care, and the physiotherapy supports the restoration of the range of the movement. [4][10]