Pediatric emergency medicine trisk 2981 2981
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Oligoarticular arthritis, meaning synovitis involving four or fewer joints, is the most
common subtype of JIA and accounts for approximately half of all cases. Oligoarticular
arthritis occurs more often in young girls, typically causing swelling, pain, and
limitation of movement in one or more large joints. ANAs are detectable in the sera of
many of these children, and their presence at any titer correlates with a higher risk for
developing iridocyclitis.
Polyarticular arthritis (both RF-positive and RF-negative) occurs more commonly in
girls. It is characterized by the insidious onset of symmetric synovitis in five or more
joints with associated morning stiffness and disability. Both large and small joints (
Fig. 101.6 ) may be involved. The presence of RF and/or anti-CCP antibodies
corresponds to an increased risk of severe, erosive arthritis, much like adult rheumatoid
arthritis. RF positivity is also associated with the development of vasculitic
complications and subcutaneous nodules. Cervical spine involvement occurs in
approximately 30% to 50% of patients with polyarticular JIA, resulting in neck pain,
stiffness, and torticollis. Unlike oligoarticular JIA, in which ocular involvement is the
cause of the most significant morbidity, polyarticular disease may result in severe
musculoskeletal disability. Thus, involvement of the temporomandibular joint may
result in restricted ability to open the mouth, involvement of the hips may permanently
affect ambulation, and small joint arthritis of the hands may compromise manual
dexterity.
The least common subtype of JIA is systemic JIA formerly known as Still disease,
which is conceptualized as an autoinflammatory, rather than autoimmune condition,
and is distinguished by its systemic features. This subtype occurs most often in boys
younger than 5 years of age, although it has been reported even in adults. Clinically,
these children often present with unremitting fevers; they may have high spiking
temperatures (39° to 41°C) for several weeks or months, classically in a twice daily
pattern. Although the child often feels stiff and does not move normally, arthritis may
not be a prominent feature at the onset of the disease. Diagnosis, therefore, generally
involves excluding infectious and malignant conditions that cause fever and systemic
inflammation, especially sepsis, leukemia, and neuroblastoma. A characteristic salmonpink evanescent maculopapular rash ( Fig. 101.7 ), diffuse lymphadenopathy, and
hepatosplenomegaly (HSM) may also be present in the early stages, offering clues to
the diagnosis. Arthralgias and myalgias are common, and pericarditis and other
serositis occur most typically in this subtype of JIA. With time, systemic features of the
disease become less prominent, and polyarticular arthritis becomes the major focus of
management. Systemic JIA is associated with considerable morbidity, including the
potentially life-threatening complication of MAS which is discussed in greater detail
below.
