Weinstein Lovell and Winters Pediatric Orthopaedics 7e

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CHAPTER 11 | Juvenile Idiopathic Arthritis

arthritis of the lower limbs. This group is less likely to meet the criteria for ERA. This arthritis is often episodic, with exacerba- tion lasting 4 to 6 weeks or, rarely, for months. The activity of the peripheral arthritis is often related to the underlying bowel disease activity. The less common type of IBD-associated arthritis is an HLA-B27–associated oligoarticular arthritis of the lower limbs, with sacroiliitis and enthesitis, and no rela- tionship to bowel inflammation (51). This form is more likely to persist and progress despite adequate control of the bowel disease. The clinical course is similar to that in other children with ERA. A comprehensive differential diagnosis of arthritis in child- hood is beyond the scope of this chapter as there are over 100 disorders in which arthritis may be a significant manifestation (69). The most common classes of disorders that must be con- sidered in the differential diagnosis of JIA include infection, postinfectious phenomenon, inflammatory arthropathies, sys- temic autoimmune disease, mechanical or orthopaedic con- ditions, trauma, and pain disorders. Often, the differential diagnosis will be determined by whether the presentation is acute, subacute, or chronic, whether the child has monoarticu- lar or polyarticular arthritis, and whether there are systemic signs such as fever (Table 11-4). Infection-Related Arthritis Septic Arthritis. Septic arthritis generally affects a single joint and is associated with fever, elevated neutrophil count, ESR, C-reactive protein (CRP), and extreme pain. Synovial fluid analysis typically reveals white cell counts of > 50,000 (70), neutrophil predominance, low glucose ( < 30 mg/dL), and a positive Gram stain. Oligoarticular JIA, in contrast, is seldom associated with systemic inflammation and joint effu- sions are often out of proportion to the reported pain. The most commonly infected joints in children are the knees, hips, ankles, and elbows. Gonococcal arthritis may present in a DIFFERENTIAL DIAGNOSIS OF PAIN AND SWELLING IN THE JOINTS IN CHILDREN

FIGURE 11-4. Ankylosing tarsitis, a complex disorder resulting in ankylosis of the foot in a child with JAS. (Courtesy of Dr. Ruben Burgos-Vargas.)

affecting predominantly the lower limb joints and entheses, is seen in 79% to 89.4%. These children tend to have fewer than 5 joints involved and rarely more than 10. At presentation, the pattern of involvement of the joints is usually asymmetric (61). Small joints of the toes are commonly involved in JAS but are seldom affected in other forms of JIA, with the exception of psoriatic arthritis. However, polyarticular and axial disease are usually evident after the 3rd year of illness (61). Children with long-standing JAS have been shown to develop tarsal bone coali- tion that has been termed ankylosing tarsitis (Fig. 11-4) (62). Outcome data for JAS are incomplete and at times contra- dictory. The prognosis of JAS has been reported as being worse according to some studies, and better according to others, than adult-onset AS (63, 64). Hip disease has been associated with a poor functional outcome (63, 65) and may require total hip arthroplasty. Inflammatory Bowel Disease–Associated Arthritis The frequency of arthritis in children with IBD has been reported to be 7% to 21%, and it usually occurs after the diagnosis of the bowel disease (66–68). Two different patterns of arthritis are seen (51). The most common type is oligo- or polyarticular

Differential Diagnosis of JIA

TABLE 11-4

Monoarticular Arthritis

Polyarticular Arthritis

Febrile Syndromes

Oligoarthritis

Polyarthritis

Systemic arthritis

Psoriatic arthritis

Malignancy:

Enthesitis-related arthritis

Lymphoid

Sarcoidosis

Neuroblastoma

Transient synovitis of the hip

Systemic lupus erythematosus Juvenile dermatomyositis

Trauma

Hemophilia

Systemic vasculitis

Pigmented villonodular synovitis

Scleroderma

Infection (viral or bacterial) Inflammatory bowel disease

Septic arthritis Reactive arthritis

Gonococcal septic arthritis

Reactive arthritis

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