Arthritis Risk Underestimated in Children With Down Syndrome

Marcia Frellick

November 18, 2019

The prevalence of arthritis in children with Down syndrome is at least two times greater than previously reported, findings from a new study suggest, but the diagnosis is often missed or significantly delayed.

There are several reasons for this, including a lack of awareness on the part of clinicians and parents that children with Down syndrome can be at high risk for what's known as arthropathy of Down syndrome, said lead researcher Charlene Foley, PhD, from Our Lady's Children's Hospital in Crumlin, Ireland.

In addition, children with Down syndrome have a tendency not to report their pain or to be slow to do so, she told Medscape Medical News.

And sometimes the signs of arthritis are attributed to the Down syndrome. "People have low expectations of children with Down syndrome reaching their gross motor milestones," Foley explained. But those assumptions can have serious consequences.

When it's not correctly diagnosed, we're going to have children with ongoing inflammation, which is going to lead to irreversible joint damage.

"When it's not correctly diagnosed, we're going to have children with ongoing inflammation, which is going to lead to irreversible joint damage," she said during a news conference at the American College of Rheumatology 2019 Annual Meeting in Atlanta. "It is erosive and aggressive, so early recognition and starting treatment is really important."

In their study, Foley and her colleagues recruited people with Down syndrome who were up to 21 years of age to undergo musculoskeletal screening and a thorough examination by a pediatric rheumatologist. A follow-up visit with a different physician specialist confirmed all suspected cases of arthropathy of Down syndrome. Physicians determined treatment in accordance with normal practice for juvenile idiopathic arthritis.

Over 18 months, 33 of the 503 study participants were identified as having arthropathy of Down syndrome.

The researchers calculated the prevalence of arthropathy of Down syndrome to be 20 per 1000 people, which is double the rate estimated in the small number of studies conducted since the condition was first named in 1984, Foley said. They also observed a significant delay in diagnosis.

A common clinical finding in the study population was the involvement of at least five joints with rheumatoid-factor-negative arthritis, she reported. A unique finding was that the small joints of the hand and wrist are more often affected in children with arthropathy of Down syndrome than in those with juvenile idiopathic arthritis.

Foley suggested the addition of a yearly musculoskeletal exam to the health surveillance guidelines for all young people with Down syndrome.

Although rheumatologists might be comfortable with such an exam, pediatricians and primary care physicians might not, so Foley offered some guidance.

"Go to the Hands"

"If you've only got a few seconds, go to the hands, because that's where you're most likely to see arthritis," she said.

Small joints were involved in 85% of the study participants, and hand joints were involved exclusively in 30%.

Changing the name from arthropathy of Down syndrome to Down syndrome–associated arthritis would better reflect the inflammatory and erosive qualities of the condition, the researchers suggest.

A related study, presented during the same news conference, also showed that arthropathy of Down syndrome is under-recognized.

There was an 11.5-month delay from symptom onset to diagnosis, said study investigator Jordan Jones, DO, a pediatric rheumatologist at Children's Mercy Kansas City in Missouri.

"Our hope is to get musculoskeletal screening into the American Academy of Pediatrics guidelines for screening for these kids," he said.

In their study, Jones and his colleagues found that the majority of their cohort — patients with arthropathy of Down syndrome younger than 18 years — presented with more than five affected joints. As in the Foley study, the affected joints were predominantly small.

The standard treatment for arthropathy of Down syndrome mirrors that for juvenile idiopathic arthritis, but efficacy is limited, he told Medscape Medical News.

"They do respond a little to that, but they still have a very high disease burden," he said. "That tells us that treating them the same as children with JIA is the best we have right now but is not good enough."

For example, "these kids have a lot of toxicity with and intolerance to methotrexate," which is a common treatment for juvenile idiopathic arthritis, Jones said.

Treatment for JIA Inadequate

It makes good sense to screen children with Down syndrome for arthritis, said Andrew Zeft, MD, a pediatric rheumatologist at the Cleveland Clinic.

Most of the evidence that supports the monitoring of children with Down syndrome for arthritis has been anecdotal, so "it's good to see studies that put it all together," he told Medscape Medical News.

But it is a challenge to assess this population, because it can be difficult to get an adequate history and discern how much discomfort children with Down syndrome are in.

And "some of the normal lymphedema that they carry makes it a bit harder to assess the joints for actual swelling," he pointed out. Plus, many of the patients have a certain amount of joint hypermobility, so it's hard to tell how much of the swelling is due to overuse, he added.

Physicians in specialty clinics are better trained and equipped to diagnose the arthritis that could be easily missed in less specialized settings, he said.

Multispecialty clinics that serve patients with Down syndrome often include endocrinologists, hematologists, neurologists, and behavioral specialists, who can look at different aspects of the syndrome, but it's not always standard to include rheumatologists. Perhaps it should be, Zeft said.

"Studies like this make it more evident that it's reasonable to have these kids screened," he added.

American College of Rheumatology (ACR) 2019 Annual Meeting: Abstracts 1817 and 380. Presented November 11, 2019.

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