When more than one member of a family is affected by multiple sclerosis (MS), their ages at disease onset are likely to be similar, but disease severity may not be. These new findings have important implications for counseling patients, according to a study published in the January 30, 2007, issue of Neurology®, the scientific journal of the American Academy of Neurology.
"We've known for some time that family influence plays a role in whether you are susceptible to MS, but it has not been clear whether your family influence affects the course of the disease," according to lead study author Alastair Compston, PhD, of the University of Cambridge Clinical School in Cambridge, United Kingdom.
To address the question of family influence on the course of the disease, researchers examined data on 2,310 individuals from over 1,000 families in which at least two members had MS. They examined age at onset, disability, disease severity, and other features of the disease.
The researchers found that age at onset of the disease was similar among family members, whether comparing parents to children or siblings with each other. They also found that siblings tended to have the same pattern of disease progression, while there was no correlation between the pattern in parents and children.
The study also showed there was no correlation between the severity of the disease in one family member and severity in another member, whether siblings or parent and child. "Disease progression is often considered the indicator of severity," said Compston. "But, we found no evidence that disease severity is more likely to be similar between two family members with MS than two unrelated people with MS."
The causes of the similarities in onset and progression pattern are largely unknown, as are the causes of MS itself. It is possible that genetic factors are responsible, but environmental factors shared by family members may also play a role.
Compston says the study's findings have significant implications for counseling patients. "People should not draw personal conclusions for their own MS prognosis and expected disease severity from observing the condition of their relatives with MS," he said.
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