Sex differences in MS: It’s the chromosomes, not just the hormones



– Hormonal differences are not the only reason that multiple sclerosis (MS) disease progression and severity differ between the sexes, according to Rhonda Voskuhl, MD, who delivered the Kenneth P. Johnson Memorial Lecture at a meeting of the Americas Committee for Treatment and Research in Multiple Sclerosis.

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“Sex differences in disease are widely prevalent across immunological and neurological diseases. For example, lupus affects women 9:1 more frequently, rheumatoid arthritis is about 3:1, and MS is 3:1,” said Dr. Voskuhl, director of the MS program and Jack H. Skirball Chair of Multiple Sclerosis Research at the University of California, Los Angeles.

However, although women are more likely to experience these diseases, men are often more severely affected by them, Dr. Voskuhl said. “Sometimes in neurodegenerative diseases like MS, we’re seeing that the men, although they get it less frequently, they do worse. ... So these are actually two very important sex differences in disease, one affecting susceptibility and frequency, and the other affecting how they do over the long run with respect to their progression and severity.”

This clinically apparent observation, known for decades, prompted Dr. Voskuhl and others to parse why sex differences exist in this gamut of diseases.

A novel animal model – the four-core genotype mouse model – has allowed Dr. Voskuhl and others to discern the contributions of hormonal versus chromosomal influences on disease susceptibility and progression. The model separates the sex chromosome complement (XX or XY) from gonadal influences, and it’s been extremely helpful in revealing the surprising influence that sex chromosomes play in MS and similar diseases, said Dr. Voskuhl in an interview.

Dr. Voskuhl is also the president-elect of the Organization for the Study of Sex Differences.

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