Ask the Doctor: Evaluating the Hereditary Risk of MS

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Dr. Jack Burks

By Dr. Jack Burks
MSAA’s Chief Medical Consultant

Q: In the previous “Ask the Doctor” column, with regard to genetic predisposition for MS, Dr. Burks noted that the risk of being diagnosed with MS when a family member has MS is about 2 percent. However, MSAA received a few letters about families with multiple members who had MS, and their risk far exceeded 2 percent. They wanted to know why this has happened in their family.

A: I am always sorry to hear when several members of a family have been affected by MS, and hope these families are able to find some relief through available treatments. These types of occurrences are fairly unique. The figures I quoted are “population averages” and these reflect the overall risk of MS in family members with MS in large-scale population studies, which have been published in the medical journals. Families with much higher rates would be considered an “outlier situation,” which is uncommon, but does occur. Outlier refers to a finding that is well outside of the expected range of values typically seen in a large population.

I normally refer to “population averages” when talking about the risk of one’s family members developing MS, unless specifically asked about “exceptions.” I don’t want to confuse and possibly upset the MS community as individuals try to understand their risk. In the past, the familial MS patients I have spoken with understand their unusual situation and tend to agree with me about not creating additional fears.

On average, the risk of MS without other close family members with MS is about one in 1,000 for the general population. With a close family member, the risk increases 20 times to about 2 percent. If a non-identical twin has MS, the risk to the other twin is about 5 percent, and this increases to 30 percent for an identical twin of a twin with MS. One genetic variant in the X chromosome may help explain the increase of frequency of MS in females.

Research efforts are now directed at finding the role of specific genetic links. Various studies have and continue to look at families with a higher risk of MS in an attempt to identify genetic markers that may increase one’s risk, and the results of such studies provide important data for researchers. However, there does not appear to be a specific “MS gene,” but rather about 200 genes that are linked to immune function and are more frequently found in people with MS.

A small risk of developing MS still exists for children of MS patients – but keep in mind that this risk is significantly less than for someone whose family has been stricken with a hereditary disease. Additionally, as you know, MS research has advanced immensely in recent years. Far more treatments have become available and many studies are pointing to the possible involvement of controllable risk factors, such as Vitamin D, weight and body-mass index (BMI), salt intake, smoking, and other possible factors. Taking all of this into consideration, the future is bright for the MS community as a whole.

Q: I am writing to you with the hope that you can help me with the recommended dosage and frequency for B12 injections. I was diagnosed one year ago with MS and the exhaustion is killing me. My doctors can’t seem to tell me what dosage to take or how often. I need the methylcobalamin form of the B12. Any help would be much appreciated.

A: Many factors contribute to the overwhelming fatigue experienced with MS. One major cause of fatigue in MS is when the protective myelin covering to the nerves of the central nervous system (CNS), which functions as a type of insulation, becomes damaged. When this occurs, more energy is required for nerve impulses to travel to their destinations. Other causes can include lifestyle factors such as lack of sleep, too much stress, using too much energy on daily tasks, and those types of things.

You are concerned about low vitamin B12 specifically, which may cause fatigue and other symptoms. A blood test is available to determine if your B12 is low. Regarding dose, I can only give you general dosage recommendations. If your doctor is unsure of the appropriate dose, he or she may also be able to refer you to a vitamin B12 authority in the area, such as a naturopathic doctor.

You specifically mention methylcobalamin, which is a natural form of vitamin B12. While cyanocobalamin is not naturally derived, it is the more commonly prescribed and more affordable version of the vitamin. However, the body quickly converts it to methylcobalamin. I have not seen any published medical information proving that one form is better or more toxic than the other. The recommended oral dosage of cyanocobalamin for vitamin B12 deficiency ranges from 125 to 2,000 micrograms (not milligrams!) per day. Oral vitamin B12 is available without a prescription, while vitamin B12 shots are available through your doctor if you cannot absorb vitamin B12 orally. The doses of methylcobalamin range between 500mcgs and 5000mcgs.

I recommend that you learn about vitamin B12 from reputable sources and a good amount of information may be found online. The Mayo Clinic provides helpful information on B12, which may be accessed by going to and searching for “vitamin B12.”

Some medications may help with MS fatigue. For example, Provigil® (modafinil) or Nuvigil® (armodafinil) may be effective, although they are not FDA-approved specifically for MS fatigue. Other drug options are also available, and you would need to discuss these treatments with your doctor to see if any are appropriate for you. Additional strategies include conserving energy, getting better sleep, reducing stress, cooling (for heat-sensitive individuals), and even exercise. For more information about combatting fatigue, please visit MSAA’s website section on this topic at

Please Submit Your Questions To:

Questions for Ask the Doctor
c/o Dr. Jack Burks
375 Kings Highway North
Cherry Hill, New Jersey 08034

Questions may also be emailed to Please be sure to include “Ask the Doctor” in the subject line.

Jack Burks, MD is the chief medical consultant for MSAA. He is an international MS neurologist, writer, lecturer, and researcher, who assists with the development of new MS therapies as well as new MS centers. He also advises patients, families, MS organizations, and healthcare groups. Dr. Burks is an adjunct professor at Nova Southeastern University and clinical professor of neurology at Florida International University. In addition, he has authored numerous textbooks, chapters, and articles on MS.