Juvenile Arthritis Can Alter Normal Growth in Children

Arthritis is often thought of as an old person's disease, but as the slogan at the top of the Arthritis Foundation's pediatric website proclaims, " Kids Get Arthritis, Too."

In fact, juvenile idiopathic arthritis, which used to be called juvenile rheumatoid arthritis, is the most common chronic joint disorder in children.

JIA encompasses seven different forms of pediatric arthritis and, like the adult forms of some arthritic diseases, such as rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis, JIA is an autoimmune disorder that occurs when, for unknown -- or idiopathic -- reasons, the body's immune system begins to attack its own healthy tissue.

The resulting inflammation can affect multiple tissues and organ systems throughout the body, including the eyes, internal organs, muscles, joints and ligaments.

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According to Harvard University's Boston Children's Hospital, one of the most important differences between JIA and adult arthritis is JIA's potential to interfere with normal growth patterns in a child's still-developing bones and tissues. The proportion of abnormally short children with JIA ranges from 10 to 40 percent.

Generalized growth retardation is more common in children who have systemic JIA. These children can suffer from profuse inflammation of multiple organ systems throughout the body, and they can be extremely ill.

"We use more steroids [in patients] with systemic JIA," says Dr. Kabita Nanda, who is an assistant professor of pediatrics in the Department of Rheumatology at the University of Washington School of Medicine in Seattle.

Yet, changes in normal growth patterns are a known side effect of treatment with steroids, especially with long-term use.

Also, the most severe growth issues are often found in children who have had long-standing chronic inflammation. This is in part due to the presence of specific inflammatory proteins -- or cytokines -- including interleukin-1, interleukin-6 and tumor necrosis factor-alpha, all of which decrease the secretion of growth hormone from the pituitary gland. They also act directly on the growth plates at the ends of bones, which is where bone growth takes place.

Abnormal growth patterns in affected joints can also be caused by changes in circulation due to inflammation. "We do see local growth changes in prolonged arthritis in any affected joints -- usually due to increased blood supply to the open growth plates in children," Nanda says.

At first, this increase in circulation causes bones to grow faster. However, over time, bone growth slows because "the affected joints mature faster and growth plates fuse faster, which can result in abnormalities and differences in the joints," says Nanda, who is also a pediatric rheumatologist at Seattle Children's Hospital.

In some cases, JIA affects one side of the body more than the other. This can cause the limbs on the affected side to grow at a different rate than the limbs on the unaffected side.

"If this happens in the legs, it can cause pelvic tilt or back problems," says Dr. Katharine Moore, a pediatric rheumatologist in Denver. "We always measure our patients' legs, and if they are uneven, then we typically will recommend a lift inside the shoe of the shorter limb," she adds.

Other factors can interfere with normal growth in chronically ill children in general, including those with JIA. These include frequent infections and long-term stress related to being chronically ill or handicapped.

Impaired bone growth does not just affect the bones in the limbs. It has also been shown to reduce both chest width and chest capacity, especially in children with poorly controlled disease and involvement of many joints. These children are often less physically active than healthy children, which affects muscle development and contributes to abnormal construction of the chest.

[See: Osteoarthritis and Activity: Walking It Out.]

Jaw growth can also be impaired.

"The temporomandibular joint of the jaw is often involved in JIA and it is often asymptomatic in the beginning," says Moore, who is an assistant professor of pediatrics and rheumatology at the University of Colorado School of Medicine.

"The TMJ is a very small joint, so it takes very little inflammation and damage to have profound impacts on jaw function and cosmetic appearance, Moore explains. "If there is inflammation or damage during periods of growth, then the jaw can develop asymmetrically."

Rheumatologists will order imaging of the jaw if they have any suspicion of inflammation of the TMJ, Moore emphasizes, "and we treat it aggressively when there is jaw involvement."

JIA's inflammation can cause pressure and pain in and around affected joints. In some cases, children and teenagers will keep an inflamed joint in the most comfortable position, which is usually bent. If a joint remains in a bent position for too long, the muscles and tendons in the joint can shorten and grow improperly, causing the joint to become stuck in a bent position.

This is called a joint contracture.

Regular stretching exercises and splinting can decrease joint tightness and help prevent joint contracture. Injection of steroids directly into the affected joint can help reduce inflammation rapidly, easing the discomfort of stretching exercises and allowing patients to perform the exercises more effectively.

To prevent growth problems, pediatric rheumatologists monitor children with JIA very closely and treat the disease aggressively to prevent serious consequences for a child's growing body. But JIA can be difficult to diagnose and treat, so obtaining an accurate diagnosis is the first hurdle that physicians must confront.

Signs and symptoms can differ considerably from child to child, and they can be contradictory or unusual. The clinical course of inflammation can also vary widely between children and can change over the course of the disease. Finally, blood tests are not reliable because markers of inflammation in the blood are often absent altogether or inconclusive.

"In contrast to adults, where the majority of patients with RA have abnormal labs, the majority of patients with JIA will have normal labs," Moore says. This is especially true when joint inflammation is limited to a small number of joints, "even if the joints are huge," Moore adds.

Impaired normal bone development is not necessarily permanent. In some children, catch-up growth is possible when the disease is in remission, either spontaneously or as a result of timely and aggressive treatment, or when steroid use is interrupted. This is especially true in younger children who have had JIA for shorter periods of time.

[See: How to Practice Yoga When You Have Arthritis or Another Chronic Condition.]

"In my experience, generalized growth retardation can be stopped and at least partially, and maybe fully, reversed, depending on how severe the [growth] retardation is and if the child's inflammation is controlled," Nanda says.

Currently, information from the Hospital for Sick Children in London says the most effective ways to decrease the chance of growth problems in children with JIA is to control inflammation with the help of currently available medications, which can include disease-modifying antirheumatic drugs and biologic response modifiers, while reducing the duration and dosage of treatment with corticosteroids when possible.

Maureen Donohue is a freelance Health reporter at U.S. News. A medical writer, editor and journalist since 1991, Maureen has written for both physicians and consumers covering a wide a variety of medical topics. Maureen's work has been published in several prestigious, peer-reviewed medical journals as well as on consumer-based websites. She has been a writer for the Stanford School of Medicine, Healthline Media, the International Medical News Group, the UC Davis Cancer Center, the Arizona Heart Institute, MedExperts International and the Sutter Institute for Medical Research. You can connect with Maureen on LinkedIn or email her at emelldee@icloud.com.