Up to 10% of children with KD initially fail to respondsatisfactorily to IVIG therapy. Most of these patients respondto retreatment with IVIG, but an alternative preparation ofIVIG may be required. Corticosteroids or infliximab arerarely used in KD, as opposed to other vasculitides, but mayhave a role during the acute phase if active carditis is apparent or for children with persistent fever after two doses ofIVIG.
Most cases resolve without sequelae. Myocardial infarction has been documented, most likely caused by stenosis of a coronary artery at the site of an aneurysm. Coronary artery aneurysms found on autopsy in older children following sudden cardiac death may have been due to past KD. Other complications are listed in Table 88-3.
IVIG reduces the prevalence of coronary artery disease from 20% to 25% in children treated with aspirin alone to 2% to 4% in children treated with IVIG and aspirin. Other than the risk of persistent coronary artery aneurysms, KD has an excellent prognosis.
The chronic arthritides of childhood include several types, the most common of which is juvenile idiopathic arthritis (JIA), formerly called juvenile rheumatoid arthritis (JRA). The classification of JIA includes several other types of juvenile arthritis, such as enthesitis-related arthritis and psoriatic arthritis. The etiology of this autoimmune disease is unknown. The common underlying manifestation of this group of illnesses is the presence of chronic synovitis, or inflammation of the joint synovium. The synovium becomes thickened and hypervascular with infiltration by lymphocytes, which also can be found in the synovial fluid along with inflammatory cytokines. The inflammation leads to production and release of tissue proteases and collagenases. If left untreated, the inflammation can lead to tissue destruction, particularly of the articular cartilage and, eventually, the underlying bony structures.
JIA is the most common chronic rheumatologic disease of childhood, with a prevalence of 1:1000 children. The disease has two peaks, one at 1 to 3 years and one at 8 to 12 years, but it can occur at any age. Girls are affected more commonly than boys, particularly with the oligoarticular form of the illness.
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JIA can be divided into several subtypes, depending on the number of joints involved (less than five versus five or more), thepresence of sacroiliac involvement, and the presence of systemicfeatures, each with particular disease characteristics (Table 89-1).Although the onset of the arthritis is slow, the actual joint swelling is often noticed acutely by the child or parent, such as after anaccident or fall, and can be confused with trauma (even thoughtraumatic effusions are rare in children). The child may developpain and stiffness in the joint that limit use, but rarely refuses touse the joint at all. Morning stiffness and gelling also can occur inthe joint and, if present, can be followed in response to therapy.
On physical examination, signs of inflammation are present,including joint tenderness, erythema, and effusion (Fig. 89-1).Joint range of motion may be limited because of pain, swelling,or contractures from lack of use. In children, because of the
Table 89-1 Features of Juvenile Idiopathic Arthritis Subgroups FEATURE OLIGOARTICULAR POLYARTICULAR SYSTEMIC ONSET SPONDYLOARTHROPATHIES No. joints <5 ≥5 Varies, usually ≥5 Varies Types of joints Medium to large (also small in extended Small to medium Small to medium Medium to large, including sacroiliac joints
Extra-articular None None Systemic features Enthesopathy, psoriasis, bowel manifestations
RF positivity + (in older children with early-onset RA)