Many facets of rheumatoid arthritis remain a mystery.

One of these unknowns is whether mothers with rheumatoid arthritis (RA) will pass the condition along to their children.

A new study published in the journal Neurology shows that while a genetic lineage of RA may not yet be certain, there may be a link between moms with RA and kids with epilepsy.

The study’s researchers concluded that children born to mothers with RA were 26 percent more likely to have epilepsy than children who had moms without the condition.

It was also noted that kids of fathers with RA did not appear to be at greater risk for developing epilepsy.

An increased risk

The study was supported by the U.S. National Institutes of Health, Danish Council for Independent Research, and Augustinus Foundation.

It focused on nearly 2 million children born between 1977 and 2008. The children were followed for an average of 16 years.

During that time, 31,491 of these children developed epilepsy, and 13,556 of these children had mothers who had RA. That group included mothers who had the condition when the child was born as well as those who were diagnosed with RA after their child’s birth.

The researchers said the children whose mothers had RA at the time of birth were up to 90 percent more likely to develop epilepsy than children whose mothers were never diagnosed with the disease.

Researchers noted that RA isn’t the only autoimmune disease that links offspring to epilepsy. Children who are born to mothers with multiple sclerosis are also at an increased risk for epileptic disorders.

Researchers pointed out that multiple sclerosis and epilepsy are both diseases that affect the brain while RA isn’t.

Looking for explanations

Why RA can increase the risk of epilepsy in children isn’t known yet.

In a press release, Dr. Ane Lilleore Rom, of Copenhagen University Hospital in Denmark, who was a lead author of the study, stated, “These results suggest that changes in the environment for the fetus may play a role in the development of epilepsy.”

“We don't know yet how this may work,” she added, “but it could involve the production of maternal antibodies that could affect the unborn child.”

Later in the published statement, Rom added that “it is new knowledge that also offspring of mothers with rheumatoid arthritis seem to have an increased risk of developing epilepsy.”

According to the latest statistics, 1 in 26 Americans will develop epilepsy in their lifetime. In two-thirds of these people, the cause is unknown.

More than 1.3 million adults live with RA — a disease for which the cause is also unknown. It is noted that in both epilepsy and RA, that causative factors can include family history, genetics, environmental factors, trauma, and lifestyle.

It is worth noting that other research has been done linking epilepsy to other autoimmune disorders in adults — including RA.