The onset of multiple sclerosis (MS) generally happens between the ages of 20 to 40 years. It can, however, develop in people outside of this age range.

Early-onset MS starts in childhood. Late-onset MS, on the other hand, can begin after the age of 50 years. The symptoms of these two conditions generally do not differ much, but they can range in severity.

The exact cause of MS is not clear. However, experts believe it to be an autoimmune condition in which the body’s immune system attacks its own tissues.

This article discusses when initial MS symptoms generally appear and the typical age at which people receive a diagnosis. It also looks at the symptoms, types of diagnosis, and treatment.

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The age of onset of MS for most people ranges from 20–40 years. Some people may receive a diagnosis at the onset. Others, however, may not get a diagnosis until years later. There is no cure for MS, which means that it is a lifelong condition.

The condition may start to develop after the age of 50 years, in which case doctors will refer to it as late-onset MS. Late-onset MS accounts for about 5% of MS cases. The symptoms are similar to those that occur in younger adults, but the condition’s progression is faster.

MS can also start in childhood and teen years. This is called early-onset MS. The onset of MS occurs before the age of 16 years in about 0.4–10.5% of cases. Symptoms do not differ significantly from adult-onset MS, but research shows seizures are generally more common.

MS has an unpredictable course that can involve various symptoms, relapses, and remissions.

The majority of people with MS have mild symptoms. However, some individuals experience difficulty with actions such as walking, speaking, and writing.

There is an accepted diagnosis of MS called the 2017 McDonald Criteria. However, there may be other symptoms that do not fit into the accepted diagnosis and which may lead to a diagnosis of other types of MS. These include:

  • clinically isolated syndrome (CIS)
  • relapsing-remitting multiple sclerosis (RMS)
  • primary progressive multiple sclerosis (PPMS)
  • secondary progressive multiple sclerosis (SPMS)

Clinically isolated syndrome (CIS)

CIS is a single episode of symptoms that may suggest that a person has MS. Experts believe that it occurs as a result of an inflammatory condition of the brain or spinal cord. CIS symptoms last at least 24 hours.

There may only be a single symptom, such as vision loss, or there may be multiple symptoms, such as vision loss alongside tingling or numbness in the legs.

When a person has CIS, a doctor will order an MRI to determine whether they have brain lesions similar to those of MS.

Brain lesions

In general, the presence of MRI-detected brain lesions means that a person may have a 70–80% risk of developing MS within several years, while an absence of lesions suggests a 20–30% likelihood of developing MS within the same time frame.

Relapsing-remitting multiple sclerosis (RRMS)

About 85% of people with MS have the subtype called RRMS. It involves episodes of attacks that develop over a few days and last at least 24 hours but not more than 1–2 months. Between attacks, symptoms may either decrease or disappear.

Most individuals who have RRMS receive a diagnosis when they are in their 20s or 30s. Aside from numbness, tiredness, and stiffness, the most common RRMS symptoms include problems with vision, thinking, bowel, bladder.

Primary progressive multiple sclerosis

About 15% of people with MS have a subtype called PPMS. Instead of relapses and remissions, individuals with PPMS experience a disability that progresses from the onset. However, PPMS can involve brief periods when the condition is stable.

The onset of most people with PPMS comes 10 years later than the onset of those with RRMS. Individuals with this subtype often experience more challenges with walking and remaining in the workforce. They may also need help performing everyday activities.

Secondary progressive multiple sclerosis

People who live with SPMS experience a gradual worsening of symptoms as time goes by. Relapses usually disappear as the condition progresses. Individuals with SPMS experience nerve loss or damage that becomes steadily more severe.

Before the use of disease-modifying therapies, about half of those with an RRMS diagnosis might transition to SPMS within 10 years, while almost all would transition to SPMS within 25 years.

However, the effect of disease-modifying treatments on altering or delaying the SPMS transition is not yet clear.

Research shows that MS affects many people, but there are certain populations in which MS is more common. According to the National MS Society (NMSS):

  • MS is three times more common in females than males.
  • The condition is more common in states that are further away from the equator.
  • Although MS occurs in people of most ancestries, it is more common in people of northern European descent.

In terms of specific risk factors for MS, the NMSS lists several:

  • Vitamin D deficiency may play a key role in the development of MS, especially in northern regions where there may be reduced exposure to sunlight.
  • Obesity in childhood and adolescence, especially in females, may increase the risk factor for MS. Obesity in adulthood may also increase the risk.
  • Smoking may increase the risk of developing MS. Research also links smoking to more severe cases and faster progression of the condition.
  • Bacteria and viruses, such as those that cause canine distemper and measles, may increase the risk of developing MS.
  • A person cannot inherit MS from a parent, but genetic factors may increase the risk of developing the condition.

Diagnosing MS can be difficult and time consuming because there is no single test that can identify it. In addition, MS symptoms fluctuate and vary, making an accurate diagnosis challenging to obtain.

Doctors may use the following information to make a diagnosis:

Many individuals with MS may be able to manage their condition without therapy. The organization notes that some medications can carry risks and may have side effects.

However, a person may want to consider options that can help manage MS and its symptoms in order to maintain their quality of life. These options may include:

  • rehabilitation
  • complimentary or alternative medication
  • managing relapses

Medication

If a person and their doctor decide that medication is necessary for treating MS, the Food and Drug Administration (FDA) has approved several drugs that may reduce the severity of MS attacks and delay the condition’s progression.

Beta-interferon drugs suppress the immune system. Examples of this drug class include interferon beta-1a (Avonex) and interferon beta-2a (Betaseron), which may be similar to naturally occurring immune system molecules.

Monoclonal antibody drugs change the immune system’s response to inflammation. Examples include ocrelizumab, recombinant anti-CD20 monoclonal antibodies, and natalizumab antibody to alpha-4 integrin.

Doctors may also prescribe muscle relaxants for stiffness and antidepressants for depression.

Generally, the age of onset for multiple sclerosis is 20–40 years, but the condition may appear at an earlier or later age.

Most individuals have a subtype of MS that alternates between relapses and remissions, while a minority have the subtype that involves regular progression from the onset.

A person may be able to reduce their risk of developing MS by getting regular exposure to sunlight, maintaining a moderate weight, and stopping smoking. After diagnosis, there are various treatment options.