Tanuja Chitnis, MD provides an overview of genetic, environmental, and hormonal risk factors for pediatric multiple sclerosis and discusses its prevalence based on age, sex, and geographic location.
Tanuja Chitnis, MD: Pediatric MS [multiple sclerosis] is defined as having a first symptom prior to the age of 18; that’s fairly consistent in most world regions. In some regions of the world, pediatrics is defined as under 16; there might be some differences when you look at literature from certain areas. It is also important to think about children and adolescents. There seems to be an important transition in adolescents, and children or adolescents over the age of 11 or 12 are more likely to have MS than those who are younger. That time around puberty seems to be an important period for developing MS. There are a lot of sex hormones that are at play here, and this might help to rev up the immune system.
Some of the risk factors for pediatric MS include environmental risk factors. I will say that about 30% of MS can be in part explained by genetic predisposition; certainly people who have a family history of MS are at a slightly higher risk of having MS themselves. However, there are a number of environmental risk factors that are very important in the overall risk of MS. This includes low vitamin D levels, sunlight exposure especially during adolescence, we heard about this at some recent meetings; obesity especially during adolescence or in the teenage years; exposure to smoking, this could be secondhand smoke, has been shown to be a risk factor both in children who might be exposed to secondhand smoke as well as in adults who might be themselves smokers; and there’s an emerging role for the diet and what’s called the gut microbiome that’s determined in part by your residence, your diet, and that seems to also play a role as a risk factor for MS. In addition, what we’re learning is that puberty or hormones may also play a role in the transition to MS. We now find that the majority of our pediatric patients with MS are postpubertal or over the age of menarche for girls, and Tanner stage 2 or higher for boys.
For the prevalence of pediatric MS, I think we should first think about what is the prevalence of MS overall? It ranges from about 30 to 100 per 100,000 people in different parts of the world. There are some parts of the world, including those that are further away from the equator, that have a higher prevalence of MS. Now, studies have consistently shown that about 5% of all patients with MS in any given center or large series are pediatric at onset. This would translate into about 5 per 100,000 in the higher-risk areas, or possibly 2 per 100,000 in the lower-risk areas. That has not been fully shown in the prevalence studies to date; the number is slightly lower. This might be because of underdiagnosis of pediatric MS, which is something that we’re trying to combat.
In terms of the prevalence in males versus females, we know that overall MS is a female-predominant disease. In different series, about 3:1 ratios have been shown for females to males in different parts of the world, and this seems to be increasing over the past few decades. In terms of pediatric MS, the prevalence is similar, the ratios in different series are about 3:1 favoring females. It’s interesting that if we look back at children versus adolescents, in children the ratio is about 1:1, and in adolescents this dramatically changes to favor females at a 3:1 ratio. Again, we see this potential role of sex hormones, especially increasing the incidence of MS in girls.
Transcript Edited for Clarity