The 8 Most Common Muscle Diseases

The most common muscle diseases are actually quite rare among the general population (except for lower back pain). Keep reading.

Written and verified by el biólogo Samuel Antonio Sánchez Amador.

Last update: 16 June, 2023

The locomotor system is made up of bones, muscles, tendons, and ligaments. There are about 650 muscle units throughout the body that are inserted into the skeleton and allow us to perform all movements with accuracy and precision, which enables our relationship with the environment. Unfortunately, there are certain common muscle diseases that make the process difficult.

Some of the diseases of the muscular system are anecdotal and easily solvable (such as contractures), but others occur congenitally and can lead to the death of the patient in a few years. Here are 10 of the most common and clinically interesting muscle diseases. Keep reading.

What are the most common muscle diseases?

Before entering fully into the most widespread diseases of the muscular system, we find it interesting to contextualize these diseases from an epidemiological point of view. The World Health Organization (WHO) provides us with the following information of interest regarding musculoskeletal disorders:

• In the world, about 1.710 million people have at least one disorder of the muscles, bones, joints, or all of these elements at the same time.
• Lower back pain is the most common musculoskeletal disorder, with 568 million people affected worldwide. By itself, this clinical picture is the leading cause of disability in 160 countries.
• There are more than 150 disorders that affect muscles, bones, and joints. These can considerably limit the mobility and dexterity of the patient, which translates into early retirement from work and society.
• Disability from these disorders has increased in recent decades and is expected to continue to rise. The fact that the world’s population lives longer and is older may have something to do with it.

Beyond data and statistics, it should also be noted that muscle diseases are divided into several classes or categories according to their etiology:

1. Primary muscle disorders: These include diseases caused by an intrinsic disorder of the muscle. They usually lead to loss of muscle fibers, atrophy, fibrosis, weakness, and chronic symptoms. Polymyositis or the group of muscular dystrophies (MD) are clear examples of this category.
2. Secondary muscle disorders: These are imbalances extrinsic to the muscle, but which damage it due to a systemic imbalance. Infections, metabolic disorders, or autoimmune diseases can trigger them.
3. Geriatric muscle diseases: As the name suggests, these conditions derive from the passing of time and the use of the muscles throughout life.

As you can see, muscle diseases aren’t only common, they’re also notable for their diversity. Here are 10 of these widespread disorders in society.

1. Mechanical or inflammatory lower back pain

Without a doubt, lower back pain is the king of musculoskeletal diseases worldwide. According to studies, this disorder affects up to 80% of the population at least once during their entire life, but curiously, less than 15% of clinical cases have a clear origin. Most lumbagos are idiopathic and patients aren’t diagnosed with an underlying cause.

Lower back pain is defined as a musculoskeletal syndrome or set of symptoms whose main sign is the presence of pain focused on the final segment of the spine (lumbar area), in the area between the lower border of the last ribs and the sacral region. It can be acute or chronic depending on its duration, and it’s usually nonspecific.

Although it’s more of a “bone pain”, lumbago falls into the category of the most common muscular diseases due to its origin in this system. It’s believed that most cases of low back pain are due to muscle tension, and therefore, they’re usually preceded by a very demanding trunk strain or poor posture.

2. Muscle contractures

According to the National Library of Medicine of the United States, contractures and cramps are included within the group of muscular diseases. Although they’re not serious physiological events, their prevalence is extremely high: For example, contractures in soccer players account for 30% of all injuries, which is equivalent to 300 days lost per team in a season.

These muscle injuries occur when the muscle is stretched or damaged beyond normal for a limited time. They’re usually the result of fatigue, improper use of the musculoskeletal system at the postural level, overexertion, or the combination of all of the above and other factors. Some of the most common symptoms of contractures are the following:

• Sudden pain and limited range of motion in the affected area
• Redness and swelling of the damaged muscle group or muscle
• Muscle spasms and stiffness
• Weakness

Most contractures are treated with rest, over-the-counter pain relievers (such as acetaminophen), and, if necessary, muscle relaxants. The repetitive administration of moist heat usually helps the condition to improve more quickly.

3. Muscular dystrophies (MDs)

Muscular dystrophies are primary inherited and progressive disorders that cause the weakening of the striated muscles over time. They’re diseases that are intrinsic to the muscle, as they’re triggered by failures in the genes that code for the proteins necessary to form this tissue. They’re distinguished from other muscle disorders by the following criteria:

1. They’re myopathies that affect the muscle in a primary way. Unlike the conditions cited above, here the error lies in the structure of the muscle unit itself.
2. They have a genetic origin. In addition, the most famous forms have a higher incidence in the male gender.
3. The course is progressive and inevitable. Patients with muscular dystrophies are usually not older than 30 years of age.
4. Muscle fibers die at some point in the disease. For this reason, the patient’s ability to move ends up being irreversibly reduced.

Below, we’ll briefly show some of the most famous MDs. Although they don’t represent the most common muscle diseases in the world as such, they’re among the most well-known.

3.1 Duchenne muscular dystrophy

This is the most common type of muscular dystrophy, with an incidence of 1 case per 5,000 live-born males. It’s due to a mutation located in the Xp21 locus, which is found on the X chromosome. As it’s a recessive disorder and due to the genetic nature of human beings, it’s an almost exclusively male condition.

The mutated gene is the one that codes for dystrophin, a protein essential for the maintenance of the muscle fiber membrane. As it can’t be repaired, the muscle gradually loses its functionality and the patient’s mobility worsens over the years. The ability to walk is lost at age 13 and almost total paralysis is reached at age 21. It has no cure and is fatal in all cases.

3.2 Becker muscular dystrophy

Again, this type of DM corresponds to a mutation in a gene located on the X chromosome, also affecting the synthesis of the dystrophin protein. However, its incidence is 1.5 to 6 cases per 100,000 live births, which makes Becker muscular dystrophy much less common than Duchenne.

As indicated by the Kidshealth portal , the signs of this disorder are evident from early childhood. Even so, the condition doesn’t begin to worsen until the child has marked weakness in the hip and pelvis, which usually occurs between 10 and 13 years of age. The onset of complications is a matter of time, but patients live an average of 40 years.

3.3 Emery-Dreifuss muscular dystrophy

According to the United States National Library of Medicine, the prevalence of this muscular dystrophy is unknown. It’s believed that one of its variants could affect 1 in 100,000 men, although the figures aren’t at all clear. Undoubtedly, it’s a much less common and less prevalent muscle disease than Becker or Duchenne muscular dystrophy.

Its inheritance pattern is quite complex, as there are different variants that are caused by mutations in the EMD, FHL1, and LMNA genes. The first 2 DNA segments are on the X chromosome, but the LMNA is on a non-sexual autosomal chromosome. This means that not all Emery-Deifuss dystrophies are more common in men than in women.

4. Myositis

The term “myositis” refers to inflammation of the muscles that are used to move the body (ie, striated or voluntary). This clinical sign can be caused by something simple and anecdotal such as an injury, but there are also certain autoimmune diseases and infections that occur with it.

Beyond the inflammation of the muscle, some symptoms that myositis is taking place are the following:

1. Tiredness after walking shortly or after standing in a specific position.
2. Muscular weakness. This can be described subjectively or require a specific test that quantifies muscle effort (such as an electromyogram).
3. Trips or falls are more common than normal.
4. Swallowing or breathing problems in the most serious cases.

As with muscular dystrophies, myositis can be divided into categories based on their etiology. We’ll present the 2 most common muscle diseases within this group in the following paragraphs.

4.1 Dermatomyositis

Dermatomyositis manifests as marked muscle inflammation and the appearance of skin rashes. The cause of this condition is currently unknown, but it’s postulated that it could be caused by a viral infection in the muscular environment or by a problem in the autoimmune system, as B and T lymphocytes are observed in the perivascular infiltrates.

According to the National Organization of Rare Disorders (NORD), 1 new case of dermatomyositis is detected per 100,000 inhabitants annually. The condition appears mainly in people between 40 and 50 years of age and is more common in women than in men, but everyone is susceptible to developing it.

4.2 Polymyositis

Polymyositis is also characterized by inflammation and muscle weakness, but it doesn’t involve skin rashes (like dermatomyositis does). In this case, the condition occurs mainly in the muscles near the trunk, is bilateral, and worsens over time. Its causes aren’t known, but it’s believed that an autoimmune attack on affected tissues could be involved.

Regarding its incidence, this is situated in 1 new case for every 125,000-130,000 inhabitants per year, which translates into an overall prevalence of 1/14,000. It’s a rare myopathy that can be confused with many of the cited pictures due to their nonspecific symptomatic manifestation.

5. Myasthenia gravis (MG)

So far, we’ve presented you with 7 common muscle diseases, including 3 types of muscular dystrophies and 2 types of myositis. We close this space with myasthenia gravis (MG), a neuromuscular disorder that causes muscle weakness due to a poor connection between effector cell groups and neurons.

According to the MedScape portal, the global prevalence of MG is 20 cases per 100,000 inhabitants, which translates to 200 patients per million people. It’s much more common in women than in men and presents with the following clinical signs:

• Extraocular muscles: Drooping of one or both eyelids and double vision.
• Facial muscles: In approximately 15% of patients, facial symptoms are present. These include speech impairment, difficulty swallowing, chewing problems, and drastic changes in facial expressions.
• Body muscles: General weakness in the neck, arms, and legs. This can cause difficulty walking.

The main cause of myasthenia gravis is autoimmune in nature, as the patient’s body produces antibodies that block or destroy muscle receptors for acetylcholine. Medications, intravenous therapy, and surgery are some of the most used approaches to alleviate the effects of this clinical picture, depending on the cause.

The most common muscle diseases and their variety

Listing the most common muscle diseases isn’t an easy task. Most of them are anecdotal in nature (contractures, injuries, and tears) and aren’t considered chronic conditions, while those that are (such as dystrophies or myositis) have an exceptionally low prevalence in the general population.

Therefore, the general idea we want you to keep in mind is that there are many muscular disorders that can take place due to the passing of time or bad movements, but the primary conditions that destroy muscle tissue are very few and are considered rare in many cases.