Juvenile Idiopathic Arthritis

There are a variety of disorders that affect the joints in children. In the past all of the disorders have been lumped together and labeled juvenile rheumatoid arthritis. Although each disorder has different clinical and radiographic manifestations and course, it may be impossible to distinguish one disorder from another at a specific time within the course of the disease. Therefore, the better term “juvenile idiopathic arthritis” has been applied to these disorders.

Juvenile idiopathic arthritis (JIA) includes juvenile-onset ankylosing spondylitis, psoriatic arthritis, inflammatory bowel disease, juvenile-onset adult-type (seropositive) rheumatoid arthritis, and Still’s disease (seronegative chronic arthritis). All of these disorders, except for Still’s disease, tend to occur in older children and therefore usually behave like their adult counterpart. Juvenile-onset adult-type (seropositive) rheumatoid arthritis differs from adult rheumatoid arthritis in two ways. First, a periostitis is frequently present in the metaphyses of the phalanges, metacarpals, and metatarsals. Second, there is significant erosive disease without joint space loss.

Still’s disease (seronegative chronic arthritis) makes up 70 percent of the cases of JIA. There are three different clinical presentations of Still’s disease, with some crossover within these three groups: (1) classic systemic disease with little to no radiographic articular changes, (2) polyarticular disease with less severe systemic manifestations, and (3) pauciarticular or monoarticular disease with infrequent systemic manifestations. Some of the children with pauciarticular or monoarticular disease progress to polyarticular disease. In all presentations the children are younger than those with other types of JIA. Because the articular changes are occurring in rapidly growing bones, the radiographic changes are quite different from those in the older child. The articular radiographic changes in Still’s disease are as follows:

1.

Periarticular soft tissue swelling
2.

Osteoporosis—juxta-articular, metaphyseal lucent bands, or diffuse
3.

Periostitis
4.

Overgrown or ballooned epiphyses
5.

Advanced skeletal maturation—premature fusion leading to decreased bone length
6.

Late joint space loss
7.

Late erosive disease
8.

Ankylosis
9.

Bilateral and symmetrical distribution in polyarticular disease; sporadic distribution in pauciarticular or monoarticular disease
10.

Distribution in hand and wrist, foot, knee, ankle, hip, cervical spine, and mandible, in decreasing order in polyarticular disease; distribution in knee, ankle, elbow, and wrist in pauciarticular or monoarticular disease

The radiographic changes are those of chronic inflammation and hyperemia in a joint that is undergoing growth and change. The changes described may occur in any type of JIA if the disease begins at an early enough age.

The hand and wrist

The hand is less frequently involved than the wrist. The distribution of the disease within the hand differs from that of adult rheumatoid arthritis in that the distal interphalangeal (DIP) joints are involved as well as the proximal interphalangeal (PIP) joints and metacarpophalangeal (MCP) joints ( Fig. 21-1 ). In early involvement there is periarticular soft tissue swelling and juxta-articular osteoporosis. In 23 percent of patients, a periostitis is present along the metaphyses and diaphyses of the phalanges and metacarpals ( Fig. 21-2 ). As the disease persists, there is overgrowth and ballooning of the epiphyses ( Fig. 21-3 ). Premature fusion of the growth plate follows, leading to brachydactyly ( Fig. 21-4 ). However, despite these changes there is usually a noticeable absence of erosive disease, and the joint spaces tend to be preserved. With continuing osteoporosis, epiphyseal compression fractures develop, leading to flattening of the metacarpal heads and “cupping” of the proximal phalangeal ossification centers ( Fig. 21-5 ). Even now growth deformity, rather than erosive disease, remains the prominent part of the radiographic picture.