summary: MS is a complex disease where both environmental and genetic factors play a role in its development. In this elegant study, the authors demonstrated that the influence of the individual genetic background on the risk of MS is modulated by the presence of some environmental factors, such as the number of years of direct exposure to younger siblings, early in life. In people with a specific genetic variant known to increase the risk of MS, having little or no exposure to younger siblings early in life, meant that they had a higher risk of developing MS than those who, despite having this “high-risk” genetic variant, had a lasting exposure to younger siblings early in life. Although these results need to be confirmed, they may help us understand better the pathogenesis of the disease, and give us hope that a high genetic risk of MS might be modulated (down-regulated) by increasing the contact with other infants early in life.

authors: van der Mei IA, Ponsonby AL, Taylor BV, Stankovich J, Dickinson JL, Foote S, Kemp A, Dwyer T

source: Ann Neurol. 2009 Sep 4;67(2):261-265

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