NEW YORK (Reuters Health) – Although patients who are diagnosed with multiple sclerosis (MS) by the age of 16 or younger take longer to reach secondary progression and irreversible disability than those diagnosed with MS at an older age, the younger group still develops these disease complications at a younger age.

According to the report in the June 21st issue of The New England Journal of Medicine, studies that have evaluated the natural history of childhood-onset MS have generally been small.

By evaluating data for close to 18,000 patients in the European Database for Multiple Sclerosis, Dr. Christian Confavreux of the University of Lyon and colleagues identified 394 patients (2.2%) diagnosed between 1976 and 2003 at the age of 16 years or younger. The mean duration of disease at the end of follow-up was 17.1 years.

The researchers also included 1775 patients from the same database who were older when diagnosed.

The estimated median time from MS onset to secondary progression was about 28 years in the child-onset group and 18 years in the adult-onset group. The age at conversion to secondary progression was 41 and 52 years, respectively.

Years from onset to irreversible disability, as assessed by the Kurtzke Disability Status Scale score, followed similar patterns. For example, a score of 6 — indicating ability to walk only with unilateral support and no more than 100 m without resting – was attained after 28.9 years in younger patients compared with 19.7 in adults. The corresponding ages were 42.2 and 54.8, respectively (p < 0.001 for all comparisons).

Patients with a younger age at onset were also about twice as likely to be female and more likely to have exacerbating-remitting initial disease course than the older patients. Early-onset patients were also "more likely to have isolated optic neuritis, isolated brain-stem syndrome, or encephalitic symptoms at presentation," Dr. Confavreux’s team writes.

"Efforts to improve therapy for MS have focused on the population with adult-onset disease," they add. "Patients with childhood-onset MS clearly deserve similar attention."