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Myelin oligodendrocyte glycoprotein (MOG) antibodies were associated with a wider spectrum of pediatric autoimmune conditions than previously thought, an observational study in Spain showed.

Of 535 children with central nervous system (CNS) demyelinating disorders or encephalitis, 116 tested positive for MOG antibodies, according to Thais Armangue, MD, of Sant Joan de Deu Children's Hospital, Josep Dalmau, MD, of the University of Barcelona and University of Pennsylvania in Philadelphia, and colleagues.

About 85% of those 116 children responded to treatment with complete or near-complete recovery, but 15% experienced severe deficits and one patient died, they reported in .

Most studies about MOG-antibody associated syndromes have focused on acquired demyelinating diseases, Dalmau said. "There have been only a few case reports, mainly including adult patients, suggesting that these antibodies can also occur in patients with encephalitis without overt clinical or MRI findings suggesting demyelinating features," he noted.

"Our study took a novel approach of prospectively examining two large cohorts of pediatric patients, one including 239 patients with demyelinating syndromes and the other 296 patients with all types of consecutively identified encephalitis in 40 Spanish centers," he told 番茄社区app.

Of the 116 children diagnosed with MOG antibodies, 94 (39%) were in the group of demyelinating syndromes and 22 (7%) were in the encephalitis group. In the first group, the researchers confirmed the association of MOG antibodies with demyelinating syndromes previously known, including acute disseminated encephalomyelitis (ADEM), optic neuritis, and myelitis.

"The major surprise came from the group of patients with encephalitis, who had syndromes in which the presence of MOG antibodies is rarely considered or even suspected," Dalmau said. "This is important because nowadays about 40% of patients with encephalitis remain without a clear etiology."

MOG antibodies damage the myelin sheath surrounding nerve fibers, causing symptoms like vision loss, muscle weakness, and pain. Many children may only experience one MOG antibody disease event, but some may relapse months or years later. The full range of diseases associated with MOG antibodies is unknown.

In this study, researchers followed children with a median age of 6 in Spanish hospitals from 2013 to 2018. Children who tested positive for MOG antibodies were assessed over a median of 42 months.

Of the 116 children who tested positive for MOG antibodies, 24% had syndromes not previously associated with MOG antibodies.

During follow-up, 33 children had relapses, including 15 children who had more than one relapse. The likelihood of relapse was similar regardless of syndrome at disease onset. Time to antibody negativity was longer in patients with relapses (HR 0.18, 95% CI 0.05-0.59).

Steroids, intravenous immunoglobulin, or plasma exchange were used in 86% of children at diagnosis and 97% of children at relapse. Rituximab (Rituxan) was used in 11 children at relapse.

Most of the 116 patients who were MOG-positive had substantial recovery (85% had a score of 0 or 1 on the , indicating no significant disability). One boy died at 4 days follow-up, and the remaining children had moderate to severe deficits. Patterns associated with poor prognosis included ADEM-like relapses with changes that resembled leukodystrophy, and extensive cortical encephalitis evolving to brain atrophy.

At last follow-up, only five patients (4%) had been diagnosed with multiple sclerosis (MS), supporting the idea that MOG antibody-associated syndromes and MS are different pathological entities, the authors noted.

This research is "a milestone in the understanding of MOG antibody-associated syndromes," wrote Romain Marignier, MD, PhD, of the Hospices Civils de Lyon in France, in an .

"In view of the very broad clinical spectrum now associated with MOG autoimmunity, the next challenge will be to identify the optimal therapeutic strategy for each clinical presentation," he added. "This objective is closely connected to a better understanding of the pathogenic role of MOG antibodies, and the need for early, robust, and specific prognostic factors of relapse and disability."

This study has several limitations, the researchers noted. It was not registry-based and could not assess the incidence and prevalence of MOG antibody-associated syndromes. Because follow-up was short, the frequency of relapses or MS development may have been underestimated. The study also did not include cognitive evaluations.

Some of the cases in the study "would have been missed if it were not for the systematic screening of our study," the researchers pointed out. "Overall, our findings are important because 85% of patients in this study had substantial recovery, illustrating the need for an update of the existing classification and terminology of MOG antibody-associated syndromes."

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