Age at onset influences juvenile dermatomyositis course

By Lynda Williams, Senior medwireNews Reporter

Children diagnosed with juvenile dermatomyositis (JDM) at age 3 years or earlier have milder symptoms than patients with later onset, research suggests.

However, the study also revealed that earlier JDM onset was associated with a higher mortality rate than later onset, and a similar risk for most complications.

"These differences in the mortality may [be] because… younger children have different variety of JDM and we need to be monitoring more diligently for the vasculopathy," suggest Anjali Patwardhan (Nationwide Children's Hospital Columbus, Ohio, USA) and co-authors.

"To be conclusive we need to continue to follow these younger children more closely, increase the sample size and look back at internal organ involvement from the time of their diagnosis."

The team reviewed medical records for all 78 JDM patients attending Nationwide Children's Hospital over the past 23 years, including 19 patients diagnosed by the age of 3 years and 59 patients diagnosed at a later age. Younger and older patients were diagnosed an average of 5.6 and 4.5 months after symptom onset, respectively, at an average age of 27 and 91 months, respectively.

The researchers report in Pediatric Rheumatology that disease course exhibited different patterns in the two groups but, contrary to previous findings, earlier onset was generally associated with a less severe form of JDM.

Younger patients were significantly more likely to be female than older patients, and significantly less likely to experience disease onset in the winter--pring months. Younger patients were also significantly more likely to experience fever before onset and have a family history of autoimmune disease than older patients, but significantly less likely to show a heliotrope rash, Gottron's sign, capillary loop abnormalities, or elevated muscle enzyme levels.

The vast majority (84.2%) of younger patients had a monocyclic disease course, with just one polycyclic and two chronic continuous cases. In comparison, 33.8% of older patients had a monocyclic disease course, 35.5% polycyclic, and 30.0% a chronic continuous disease pattern.

There were two JDM-related deaths in the younger patients but none in the older patients, a significant survival difference.

Younger patients were less likely than older patients to have active disease 5 years (9 vs 36%) and 10 years (9 vs 45%) after diagnosis, and to experience osteonecrosis (5 vs 17%). Other complications such as serious infection and calcinosis did not significantly differ between the groups.

The groups did not differ with regard to initial oral steroid dose, receipt of methotrexate at diagnosis, or use of immunosuppressants. But younger patients had a shorter mean and maximum duration than older patients for both methotrexate (24.31 vs 35.17 months, and 51 vs 124 months, respectively) and oral steroids (16.8 vs 33.3 months, and 50 vs 151 months, respectively).

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