Duchenne Muscular Dystrophy (DMD)


Muscular dystrophy (MD) prognosis varies depending on the type of disease a patient has. There are many types of MD caused by mutations in various genes. Some types can be severe and progress rapidly, while others may be mild, appear later, and progress slowly.1

The main symptom of MD is progressive muscle weakness and atrophy. In some types of MD,  weakness is so mild that it only causes moderate disability late in life. In others, muscle weakness can cause functional disability and loss of ambulation early in life and lead to complications that can be life-threatening.2

Duchenne Muscular Dystrophy Prognosis

In Duchenne muscular dystrophy (DMD), mutations in the DMD gene lead to a lack of dystrophin protein being produced. This protein is essential for the maintenance of muscle cell health. In its absence, muscle cells die and are gradually replaced by scar tissue.

Because the DMD gene is located on the X chromosome, the disease mainly affects boys. Symptoms usually first appear between ages 3 and 5 and mostly affect muscles in the pelvic area before moving to the shoulder muscles. As the disease progresses, other muscles in the body, including those used for breathing and cardiac muscles, also become involved. Patients usually lose ambulation in their teenage years and may eventually need respiratory support.

Early studies reported that most patients with DMD died in their late teens or 20s due to lung infections or cardiomyopathies. However, with advances in respiratory and cardiac care, survival rates are improving.3

Becker Muscular Dystrophy Prognosis

Becker muscular dystrophy (BMD) is also caused by mutations in the DMD gene. However, because these mutations do not disrupt the reading frame of the gene, cells can still produce dystrophin protein that is shorter but still functional. As a result, the symptoms of the disease appear much later, usually when a patient is in their teens or young adult years although they can appear any time between ages 5 and 60. Muscle weakness usually starts in the hips and pelvis and then moves to the thighs and shoulders. BMD also affects cardiac muscles.4 

The rate of disease progression also varies greatly from patient to patient but most maintain ambulation until at least age 16 and sometimes throughout their life.5 On average, patients with BMD survive into their mid-40s. The most common cause of death is heart failure due to cardiomyopathy.6 

Read more about Becker Muscular Dystrophy.

Facioscapulohumeral Muscular Dystrophy Prognosis

In facioscapulohumeral muscular dystrophy (FSHD) symptoms usually begin before age 20 with muscle weakness around the eyes and mouth. Other affected muscles include those of the shoulders, abdomen, upper arms, and lower legs.7

FSHD can be divided into 2 types based on age at onset of symptoms. In infantile onset FSHD, symptoms usually appear before age 5 and scapulohumeral muscle weakness appears before age 10. About 5% to 10% of FSHD cases are infantile onset. In most cases, however, symptoms appear in adolescence or adulthood.8

The progression of symptoms is usually slow. About 20% to 25% of patients with classic onset disease lose ambulation after age 50. However, the disease seems to progress more rapidly when symptoms appear early and patients usually lose ambulation when they are in their 20s or 30s.8  

Research has shown that the average life expectancy of patients with FSHD is 39 years from age of diagnosis.9

Limb-Girdle Muscular Dystrophy Prognosis

Limb-girdle muscular dystrophy (LGMD) is a group of muscular dystrophies characterized by muscle weakness around the shoulder girdle and hips. There are at least 16 different genetic forms of LGMD. As the disease progresses, other muscle groups also become involved. Patients usually lose ambulation 20 to 30 years after diagnosis.10

The disease also affects the heart and can cause cardiac muscle weakness and abnormal electrical activity. This can lead to palpitations, fainting, and sudden death. Although most patients with the disease live into adulthood, they do not reach their full life expectancy.10 

Emery-Dreifuss Muscular Dystrophy Prognosis

In Emery-Dreifuss muscular dystrophy, muscle weakness starts in the upper arms and lower legs. This is followed by weakness in the shoulders and hips. The disease also affects the heart muscle.11 

The age of onset and progression rate of the disease varies greatly between patients. The first signs of the disease usually become apparent by age 10. The disease may progress more slowly during childhood with more rapid progression in adulthood. Patients usually maintain mobility throughout their lives. Heart problems usually become apparent in the second decade of life and can be life-threatening.12 

Oculopharyngeal Muscular Dystrophy Prognosis

The symptoms of oculopharyngeal muscular dystrophy (OPMD) usually appear between ages 40 and 60 and include muscle weakness around the eyes and in the throat. The disease usually progresses slowly but progression seems to be faster in homozygote patients compared to heterozygote ones.13

OPMD also affects the central nervous system and leads to cognitive decline and psychotic problems. Life expectancy is reduced compared to the general population.14 

References

  1. Muscular dystrophy. Mayo Clinic. Accessed May 22, 2021.
  2. Duchenne muscular dystrophy. National Organization of Rare Disorders. Accessed May 22, 2021.
  3. Passamano L, Taglia A, Palladino A, et al. Improvement of survival in Duchenne muscular dystrophy: retrospective analysis of 835 patients. Acta Myol. 2012; 31(2):121–125.
  4. Becker muscular dystrophy (BMD). Muscular Dystrophy Association. Accessed May 22, 2021.
  5. Morrison LA. Chapter 2 – Dystrophinopathies. Handbook of Clinical Neurology. 2011;101:11-39. doi:10.1016/B978-0-08-045031-5.00002-5
  6. Becker muscular dystrophy. Genetic Testing Registry. Accessed May 22, 2021.
  7. Facioscapulohumeral muscular dystrophy (FSH, FSHD). Muscular Dystrophy Association. Accessed May 22, 2021.
  8. When your child is diagnosed with FSHD. FSHD Society. Accessed May 22, 2021.
  9. Deenen JCW, Arnts H, van der Maarel SM, et al. Population-based incidence and prevalence of facioscapulohumeral dystrophy. Neurology. 2014;6;83(12):1056-9. doi:10.1212/WNL.0000000000000797
  10. Limb-girdle muscular dystrophies. MedlinePlus. September 17, 2019. Accessed May 22, 2021.
  11. Emery-Dreifuss muscular dystrophy. Genetic and Rare Disease Information Center. Accessed May 22, 2021.
  12. Bonne G, Leturcq F, Yaou RB. Emery-Dreifuss muscular dystrophy. GeneReviews. Accessed May 22, 2021.
  13. Oculopharyngeal muscular dystrophy. National Organization of Rare Disorders. Accessed May 22, 2021.
  14. Blumen SC, Bouchard J-P, Brais B, et al. Cognitive impairment and reduced life span of oculopharyngeal muscular dystrophy homozygotes. Neurology. 2009;25;73(8):596-601. doi:10.1212/WNL.0b013e3181b388a3

Article reviewed by Harshi Dhingra, MD, on July 1, 2021.