Is multiple sclerosis genetic?
Multiple sclerosis (MS) is a chronic, unpredictable, progressive and often disabling neurological disease that affects the central nervous system (CNS), composed of the brain, spinal cord and optic nerves.
In this brief guide we are going to answer the question ‘’Is multiple sclerosis genetic?’’ we will explain what is multiple sclerosis, its types and what are its causes.
Is multiple sclerosis genetic?
No, multiple sclerosis is not genetic. Although MS is not hereditary, those who have a first-degree relative, such as a sibling or parent, with the disease are at a higher risk of developing MS. In fact, populations with higher rates of MS share certain genes.
Families in which more than one person has the disease have been found to have common genetic factors. For that reason, researchers believe that genetic factors may increase the predisposition to develop MS.
What are the causes of Multiple Sclerosis?
Cases of multiple sclerosis increases as we move away from the equator. That is why scientists analyzing disease patterns are investigating whether geographic variations (such as sunlight duration and changes in temperature and humidity) and demographic variations (such as age, gender, ethnicity, and migration patterns), as well as diet, infections, and exposure to certain environmental toxins can cause or aggravate multiple sclerosis.
So far, no specific environmental factor has been detected that triggers the disease, so it is likely to be due to the conjugation of several factors.
The most recent evidence suggests that the more we are exposed to sunlight and the higher the level of naturally produced vitamin D, the lower the risk of multiple sclerosis, probably because this vitamin strengthens immune function.
Studies on population migrations support the idea that exposure to certain environmental agents before puberty may predispose us to develop multiple sclerosis later in life.
In fact, those who were born in an area considered to be at high risk for developing multiple sclerosis and moved to an area with a lower risk before the age of 15 years have decreased odds of developing the disease.
Research has also shown that smoking increases the risk of developing MS and correlates with a more severe form of the disease and more rapid disease progression. In addition, exposure to toxic substances, such as solvents or heavy metals, has been associated with the development of MS, although the results are inconclusive.
It has also been found that consuming too much salt can cause the immune system to cause autoimmune diseases.
Finally, it is important to note that although physicians and researchers have suggested that infections may be a cause of multiple sclerosis, this theory has not been scientifically proven.
What are the symptoms of Multiple Sclerosis?
Although sclerosis is not an inherited disease, some studies suggest that genetics may play a role in a person’s susceptibility to the disease.
If there is an affected person in the family, his or her first-degree relatives have a 1 to 10 percent chance of developing the disease. Some peoples such as Gypsies, Eskimos and Bantus never suffer from multiple sclerosis.
Others, such as Native American Indians, Japanese and other Asian peoples, have a very low incidence rate. It is not clear whether this is due to genetic or environmental factors. This appears to be a disease of temperate rather than tropical climates (i.e., there is more multiple sclerosis the farther one lives from the equator).
In the northern European region and in North America, especially in Scandinavia, Scotland and Canada, there is a high prevalence of multiple sclerosis, perhaps reflecting a specific susceptibility of the indigenous population. Women are more likely to get multiple sclerosis than men.
In general, multiple sclerosis is a disease in young adults, the average age of onset is 29-33 years, but the age range of onset is very wide, approximately from 10 to 59 years; and females suffer from the disease somewhat more frequently than males.
Main symptoms of multiple sclerosis:
- Double or blurred vision
- Speech problems
- Weakness in the limbs
- Loss of strength or sensation in some part of the body
- Dizziness or lack of balance
- Tingling sensation or numbness
- Urinary control problems
- Difficulty walking or coordinating movements
At first, flare-ups of any of these symptoms occur more often and the patient recovers from them more quickly. Other times it takes a long time for the disease to show up.
Most people with multiple sclerosis experience more than one symptom and, although there are some very common ones, each patient usually presents a combination of several of them, the possibilities of which may be:
- Visual: Blurred vision, double vision, optic neuritis, rapid and involuntary eye movements, total loss of vision (rarely).
- Balance and coordination problems: Loss of balance, tremors, unsteadiness in walking (ataxia), dizziness and lightheadedness, clumsiness in one limb, and lack of coordination.
- Weakness: This may particularly affects the legs and gait.
- Muscle stiffness: The altered muscle tone may produce muscle stiffness (spasticity), which affects.
- Muscle spasms and pain are also frequent.
- Altered sensations: Tingling, numbness (paresthesia), burning sensation, other undefinable sensations.
- Abnormal speech: slowness of articulation, slurred speech, changes in speech rhythm.
- Fatigue: a debilitating type of general fatigue that cannot be anticipated or is excessive in relation to the activity being performed (fatigue is one of the most common and troublesome symptoms of MS).
- Bladder and bowel problems: need to urinate frequently and/or urgently, incomplete voiding or voiding at inappropriate times; constipation and, rarely, loss of sphincter control (incontinence).
- Sexuality and intimacy: impotence, decreased arousal, loss of pleasurable sensation, sensitivity to heat: heat very often causes transient worsening of symptoms.
- Cognitive and emotional disorders: problems with short-term memory, concentration, judgment or reasoning.
- Some MS patients also report that these symptoms are aggravated by heat, either in temperature or applied, for example, in hot showers. Therefore, they have to use temperature-reducing measures such as air conditioning or drinking cold liquids to counteract these more severe symptoms.
Types of Multiple Sclerosis
Isolated Clinical Isolated Syndrome (ACS)
The first episode of neurological symptoms is caused by inflammation and myelin damage (demyelination) in the central nervous system (CNS). This characteristic episode of MS must last for at least 24 hours but does not yet meet the criteria for a diagnosis of the disease, as ACS does not always progress to multiple sclerosis.
If ACS is combined with lesions in the brain similar to those seen in MS on magnetic resonance imaging (MRI), there is a high likelihood of the second episode of neurological symptoms, in which case relapsing-remitting MS is diagnosed.
Relapsing-remitting multiple sclerosis (RRMS)
This is the most common form of the disease, accounting for approximately 85% of cases. It is characterized by the presence of well-defined attacks or episodes of new or more acute neurological symptoms (known as relapses or exacerbations) that may last several days or weeks.
The type and amount of symptoms experienced during a relapse, as well as the frequency of relapses, varies from case to case. Symptoms may be relieved or even disappear and are said to have subsided. During these periods of partial or complete recovery (remissions), the disease does not progress, at least apparently.
This pattern of relapse and remission may continue for several years. Initially, after a relapse, the person may recover completely, or nearly so. Eventually, usually after 5 to 15 years, some of the symptoms of multiple sclerosis become permanent due to the buildup of scar tissue in the brain and gradual nerve damage.
Primary progressive multiple sclerosis (PPMS)
This course of the disease affects approximately 15% of people with multiple sclerosis and is characterized by a gradual worsening from the time symptoms begin, without the presence of relapses or early remissions.
Secondary Progressive Multiple Sclerosis (SPMS)
After an initial period of RRMS, the disease progresses with a steady worsening of symptoms, with or without occasional relapses. It is estimated that approximately two-thirds of people with RRMS will develop SPMS within 15 years.
There is no evidence that multiple sclerosis is directly inherited, but studies have shown that genetic factors may increase vulnerability to developing the disease.
In this brief guide we answered the question ‘’Is multiple sclerosis genetic?’’ we explained what is multiple sclerosis, its types and what are its causes.
If you have any questions or comments please let us know!
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Leray E, Moreay T, Fromont A, Edan G. Epidemiology of multiple sclerosis. Rev Neurol (Paris). 2016; 172(1):3-13.