Duchenne Muscular Dystrophy (DMD)


Muscular dystrophy (MD) is a group of genetic diseases characterized by progressive muscle weakness and atrophy. There are different types of muscular dystrophy based on the causative genetic mutation. These differ in terms of symptoms, age of onset, progression rate, and severity.

Muscular Dystrophy Symptoms in Children

Most types of MD are diagnosed in children when the patient is aged 3 to 6 years.1 The early symptoms of MD in children include walking delays, difficulty rising from a sitting or lying position, frequent falls, and muscle weakness in the shoulders and pelvis. Other common symptoms of MD in children include clumsiness, difficulty climbing stairs, inability to jump or hop, walking on toes, leg pain, weakness in facial muscles, and the inability to close eyes or whistle.

Muscular Dystrophy Symptoms in Adults

As MD progresses, symptoms may worsen and new ones may arise. Common symptoms of MD in adults include progressive muscle weakness affecting breathing and swallowing, scoliosis, contracture, and cardiomyopathy.2 However, these vary between types of MD. 

Duchenne Muscular Dystrophy Symptoms

The symptoms of Duchenne muscular dystrophy (DMD) usually appear between ages 2 and 3. Muscle weakness first affects the proximal muscles and then moves onto the distal muscles. The lower extremities are usually affected before the upper extremities.3

Children affected by the disease usually have enlarged calves due to fat deposits replacing muscle tissue. Gowers sign is also a characteristic pattern observed in children with DMD where they “climb up” their thigh with the help of their hands to overcome pelvic and proximal lower limb muscle weakness.4

As the disease progresses, cardiac and respiratory muscles are also affected, causing cardiomyopathy and acute respiratory failure.3

Facioscapulohumeral Muscular Dystrophy

Muscle weakness and atrophy in facioscapulohumeral muscular dystrophy (FSHD) usually start in the muscles around the eyes and mouth, shoulders, and upper arms. It then moves to the abdominal muscles and muscles of the lower legs. 

Other symptoms may include the inability to raise the arms above shoulder level, hand and finger weakness, foot drop, and scoliosis.5 Muscle weakness is usually asymmetrical. In more severe forms of the disease, hearing and vision may also be affected.

Limb-Girdle Muscular Dystrophy Symptoms

There are different types of limb-girdle muscular dystrophy (LGMD) and symptoms may vary depending on the type of disease.6 The time of onset of the symptoms also varies with some patients showing symptoms in early childhood (noncongenital) with others not having any symptoms until adulthood. 

The main symptom of LGMD is muscle weakness and atrophy in the proximal or distal-proximal muscles of the hips and shoulders. As the disease progresses, muscle weakness may spread to the distal areas. Other symptoms of LGMD include scoliosis, lordosis, contracture, and calf muscle hypertrophy. In later stages of the disease patients may develop cardiomyopathy, dysphagia, dysarthria, and respiratory difficulties.7

Distal Muscular Dystrophy Symptoms

Distal muscular dystrophy usually affects the muscles in the lower extremities causing difficulty with fine motor skills and foot drop. It can also affect the muscles in the neck, hands, hips, and trunk. 

There are different types of distal muscular dystrophy that can affect specific groups of muscles. For example, Welander distal myopathy usually affects the arms first and then the legs. Finnish (tibial) distal myopathy usually affects the legs and causes patients to lose ambulation as the disease progresses. Miyoshi distal myopathy causes weakness in the calf muscles usually leading to the loss of ambulation. Nonaka distal myopathy affects the muscles near the shin and then moves to the upper legs, upper arms, and neck. Hereditary inclusion-body myopathy type 2 usually affects the foot and thigh muscles. Finally, distal myopathy with pharyngeal weakness affects the voice, hands, and legs.8

Oculopharyngeal Muscular Dystrophy Symptoms

Oculopharyngeal muscular dystrophy affects a very specific group of muscles such as those around the muscles of the upper eyelids and in the throat.9 In rare cases, the disease may also affect the muscles in the upper extremities. 

The most common initial symptoms of oculopharyngeal muscular dystrophy are bilateral ptosis (drooping of eyelids) and dysphagia (difficulty swallowing). Some patients may also experience diplopia.

Muscular Dystrophy Symptoms and Treatment

The symptomatic treatment of MD includes medical treatment with corticosteroids to delay the progression of the disease, and physical, occupational, and speech therapy to increase muscle strength and improve patients’ quality of life.10 In more severe cases, patients may need respiratory support and a pacemaker to treat heart rhythm problems. 

Medical devices such as walkers and wheelchairs may be prescribed to increase mobility and prevent falls. Finally, surgery may be necessary in some instances to correct scoliosis (curved spine) and contracture.

References

  1. Pediatric muscular dystrophies. Children’s National. Accessed May 20, 2021. 
  2. Muscular dystrophy: hope through research. National Institute for Neurological Disorders and Stroke. August 2013. Accessed June 25, 2021.
  3. Duchenne muscular dystrophy (DMD). Muscular Dystrophy Association. Accessed May 20, 2021.
  4. Shrestha S, Munakomi S. Gower Sign. Stat Pearls. February 23, 2021. Accessed May 20, 2021.
  5. Statland JM, Tawil R. Facioscapulohumeral muscular dystrophy. Continuum (Minneap Minn). 2016;5; 22(6):1916–1931. doi: 10.1212/CON.0000000000000399
  6. Angelini C. LGMD. Identification, description and classification. Acta Myol. 2020;39(4):207–217. doi: 10.36185/2532-1900-024
  7. Limb-Girdle muscular dystrophies. National Organization for Rare Disorders. 2012. Accessed June 25, 2021.
  8. Distal myopathy. National Organization for Rare Disorders. 2007. Accessed June 25, 2021.
  9. Distal muscular dystrophy. Cedars Sinai. Accessed May 20. 2021.
  10. Oculopharyngeal muscular dystrophy. National Organization of Rare Disorders. Accessed May 20, 2021.
  11. Muscular dystrophy. Cleveland Clinic. June 22, 2020. Accessed May 20, 2021

Article reviewed by Debjyoti Talukdar, MD, on July 1, 2021.