To investigate the prevalence of autoimmune disease in pediatric patients with opsoclonus-myoclonus syndrome (OMS) and their first and second-degree relatives and to compare the rates in those with and without a paraneoplastic cause.

OMS is a rare autoimmune disorder characterized by involuntary rapid eye movements, myoclonus, and ataxia. Roughly 50% of cases in children are paraneoplastic while the remainder are infection-associated or idiopathic. Although thought to be autoimmune in nature, research in to personal and familial autoimmunity, which would be presumably be increased in this population, has been limited. One European study in a homogeneous cohort reported autoimmunity in 15.8% of parents compared to 2% of controls. This finding has not been assessed in other, more diverse OMS populations, nor have there been comparisons of autoimmune histories between patients with paraneoplastic and idiopathic etiologies of OMS.

A single center cohort study of consecutively evaluated children with OMS was performed. Parents of patients were administered surveys on familial autoimmunity. The Fisher’s exact test and parametric and non-parametric t-test were used to compare groups.

Thirty-five patients (18 paraneoplastic, median onset 19.0 months; 17 idiopathic, median onset 25.0 months) and 68 first-degree relatives (median age 41.9 years) were enrolled. One patient developed systemic lupus erythematosus 7 years after OMS onset. Among 68 first-degree relatives, 18 (26%) had autoimmune disease. Paraneoplastic OMS was associated with a 38% rate of autoimmunity in a first-degree relative compared with 29% in idiopathic OMS (p=0.49). Amongst second-degree relatives, 33 had autoimmune disease, with thyroid and rheumatologic conditions being the most commonly reported.

In a cohort of pediatric patients with OMS, there were elevated rates of first- and second-degree autoimmune disease with no difference in rates observed between paraneoplastic and idiopathic etiologies, suggesting a genetic autoimmunity contribution to the development of OMS in children.